Daniel L. Clarke-Pearson
Emily Ko
Lisa Abaid
Kevin Schuler
• The preoperative evaluation should be complete and thorough, taking into account the essential aspects of the patient’s general medical condition and prior surgical history. The risks, benefits, and potential complications of the surgical procedure should be discussed with the patient, including the most frequent complications of the particular surgical procedure. Alternative management, if any, should be presented.
• A calculated body mass index (BMI) can be used as a surrogate marker for nutritional status.
• Careful and meticulous fluid and electrolyte management is essential for all patients undergoing major surgical procedures.
• Although satisfactory analgesia is easily achievable with available methods, patients continue to suffer unnecessarily from postoperative pain.
• Prophylactic antibiotics should be employed judiciously. Prompt identification of perioperative infections and their specific treatments are critical to minimize the impact of this common morbidity.
• Early in the clinical course, a postoperative small bowel obstruction may exhibit signs and symptoms identical to those of ileus. Initial conservative management as outlined for the treatment of ileus is appropriate.
• Because pulmonary embolism is the leading cause of death following gynecologic surgical procedures, the use of prophylactic venous thromboembolism regimens is an essential part of management. In patients at moderate risk, intermittent pneumatic compression (IPC) during and after gynecologic surgery reduces the incidence of deep venous thrombosis on a level similar to that of low-dose or low molecular weight heparin. A combination of mechanical (IPC) and pharmacologic prophylaxis is recommended for high-risk patients.
• Patients who are predisposed to cardiovascular, respiratory, and endocrine illnesses must be thoroughly evaluated preoperatively. Coronary artery disease and chronic obstructive pulmonary disease (COPD) are major risk factors for patients undergoing abdominal surgery. Patients with hypertension should receive medication to control their blood pressure before surgery. Perioperative management of medical complications must be prompt and meticulous.
The successful outcome of gynecologic surgery is based on thorough evaluation, careful preoperative preparation, and attentive postoperative care. This chapter discusses approaches to the general perioperative management of patients undergoing major gynecologic surgery with specific medical problems that could complicate the surgical outcome.
Medical History and Physical Examination
Gynecologic surgery should be undertaken only after gaining a thorough understanding of a patient’s medical history and performing a complete physical examination.
1. The medical history should include detailed questions to identify any medical illnesses that might be aggravated by surgery or anesthesia. Coronary artery disease, pulmonary diseases, and obesity are the most common causes of postoperative complications.
2. Medications currently being taken (including nonprescription drugs) and those discontinued within the month before surgery should be recorded. Information about the use of “alternative therapies,” herbs, and vitamins should be elicited (1,2). Specific instructions must be given to the patient regarding the need to discontinue any medications before surgery (e.g., aspirin, antiplatelet agents, diuretics, hormone replacement, or oral contraceptives), and those medications that should be continued (e.g., beta-blockers, α-2 agonists, statins, H2 blockers, and proton pump inhibitors). Collaboration with the anesthesiologist in making decisions about continuing preoperative medications is essential. In the case of herbal medications, there is no evidence that herbal medications improve surgical outcomes and many may increase complications (Table 22.1). It is recommended that all herbal medications be discontinued at least a week before surgery.
Table 22.1 Potential Effects of Common Herbal and Dietary Supplements
|
Herb/Dietary Supplement |
Potential Perioperative Effect |
|
Aconite |
Potential ventricular arrhythmias |
|
Aloe |
May potentiate thiazides |
|
Black cohosh |
May potentiate hypotensive effects |
|
Danshen |
May cause bleeding |
|
Dong quai |
May cause bleeding |
|
Echinacea |
Allergic reactions; decreased effectiveness of immunosuppressants |
|
Ephedra/ma huang |
Risk of myocardial ischemia and stroke from tachycardia and hypertension; ventricular arrhythmias with halothane; long-term use may cause intraoperative hemodynamic instability; life-threatening interaction with monoamine oxidase inhibitors, anesthesia, potential for withdrawal |
|
Licorice |
May cause hypertension and hypokalemia |
|
Senna |
May cause electrolyte imbalance |
|
St. John’s wort |
Induction of cytochrome p450 enzyme; excessive sedation and delayed emergence from general anesthesia; potential serotonin syndrome if used in combination with other serotoneregic agents |
|
Valerian |
Excessive sedation and delayed emergence from general anesthesia; benzodiazepine-like acute withdrawal |
|
Yerba mate |
May cause hypertension or hypotension and excess sympathetic nervous system stimulation |
3. The patient should be questioned regarding known allergies to medications (e.g., sulfa and penicillin), foods, or environmental agents. A history of sensitivity to shellfish may be the only clue of iodine sensitivity, which could be fatal if intravenous contrast is administered without corticosteroid preparation.
4. Previous surgical procedures, and the patient’s course following those surgical procedures, should be reviewed to identify and protect against potential complications. The patient should be asked about specific complications, such as excessive bleeding, wound infection, venous thromboembolism, peritonitis, or bowel obstruction. Prior pelvic surgery should alert the gynecologist to the possibility of distorted surgical anatomy such as adhesions or ureteral stricture from previous periureteral scarring. In such cases, it may be prudent to identify any preexisting abnormality by performing computed tomography (CT) or other imaging. Many patients may not be entirely clear about the extent of the previous surgical procedure or the details of intraoperative findings. Therefore, operative notes from previous procedures should be obtained and reviewed.
5. Family history may identify familial traits that might complicate planned surgery. A family history of excessive intraoperative or postoperative bleeding, venous thromboembolism, malignant hyperthermia, and other potentially inherited conditions should be sought.
6. The review of systems should be detailed to identify any coexisting medical or surgical conditions. Inquiry about gastrointestinal and urologic function is particularly important before undertaking pelvic surgery because many gynecologic diseases involve adjacent nongynecologic viscera. The patient may have less serious symptoms, which could be corrected along with performing the primary surgery (e.g., stress urinary incontinence, fecal soiling, symptomatic cystocele).
7. Although many women undergoing gynecologic surgical procedures are otherwise healthy, with pathology identified only on pelvic examination, other major organ systems should not be neglected in the physical examination. Identification of abnormalities, such as a heart murmur, pulmonary compromise, hernia, or osteoarthritis of hips or knees should lead the surgeon to obtain additional testing and consultation to minimize intraoperative and postoperative complications.
Laboratory Evaluation
“Routine” preoperative laboratory testing of healthy women is to be discouraged as abnormal results are infrequent and are rarely of consequence in the surgical or anesthetic management of the patient (3). Despite well-established guidelines, approximately 90% of patients undergo unnecessary testing in a major university medical center (4). The selection of appropriate preoperative laboratory studies should depend on the type of the anticipated surgical procedure and the patient’s medical status.
Chest x-ray:
Over age 60 years undergoing major surgery
American Society of Anesthesiologists (ASA) 3 or greater
Cardiovascular disease
Electrocardiogram (5):
Over age 60 years undergoing major surgery
Any cardiovascular disease or diabetes
Complete blood count:
Major surgery
ASA 3 or greater
Renal function:
Recognized renal or cardiovascular disease
Coagulation studies (activated partial thromboplastin time [APTT], prothrombin time [PT], platelet count):
Not recommended unless patient has history of bleeding or liver disease (6)
Urinalysis:
Not recommended; may be considered given symptoms or history
Imaging of adjacent organ systems should be undertaken in individual cases as follows:
1. CT urography is helpful to delineate ureteral patency and course, especially in the presence of a pelvic mass, gynecologic cancer, or congenital müllerian anomaly. A CT urogram is not of value in the evaluation of most patients undergoing pelvic surgery (7).
2. Upper endoscopy, colonoscopy, barium enema, or upper gastrointestinal studies with small bowel assessment may be of value in evaluating some patients before undergoing pelvic surgery. Because of the proximity of the female genital tract to the lower gastrointestinal tract, the rectum and sigmoid colon may be involved with benign (endometriosis or pelvic inflammatory disease) or malignant gynecologic conditions. Conversely, a pelvic mass could have a gastrointestinal origin such as a diverticular abscess or a mass of inflamed small intestines (Crohn disease) or, rarely, a gastric or pancreatic carcinoma. Any patient with gastrointestinal symptoms should be further evaluated.
3. Other imaging studies, including ultrasonography, CT scanning, or magnetic resonance imaging (MRI), may be useful in selected patients such as in the evaluation of a pelvic mass.
Preoperative Discussion and Informed Consent
The preoperative discussion should include a description of the surgical procedure, its expected outcome and risks and is the basis for obtaining signed informed consent (8,9). Informed consent is an educational process for the patient and her family and fulfills the physician’s need to convey information in understandable terms. The items listed in Table 22.2 should be discussed, and, after each item, the patient and family should be invited to ask questions. Documentation of the discussion is an important component of the patient’s record that the physician should always include with the preprinted consent form.
Table 22.2 Outline of Key Points of the Preoperative Informed Consent Discussion
|
1. The nature and extent of the disease process 2. The extent of the actual operation proposed and the potential modifications of the operation, depending on intraoperative findings 3. The anticipated benefits of the operation, with a conservative estimate of successful outcome 4. The risks and potential complications of the surgery 5. Alternative methods of therapy and the risks and results of those alternative methods of therapy 6. The results likely if the patient is not treated |
Following are components of the informed consent process:
1. A discussion of the nature and the extent of the disease process should include an explanation in lay terms of the significance of the disease or condition. Printed materials, computer-based learning programs, and videotapes may assist in this process. The patient’s competency to understand the discussion and written consent should be assessed. If the patient speaks a different language, a qualified interpreter should be present and the presence of the interpreter documented.
2. The goals of surgery should be discussed in detail. Some gynecologic surgical procedures are performed purely for diagnostic purposes (e.g., dilation and curettage, cold knife conization, diagnostic laparoscopy), whereas most are aimed at correcting a specific problem. The extent of the surgery should be outlined, including which organs will be removed. Most patients like to be informed regarding the type of surgical incision and the estimated duration of anesthesia.
3. The expected outcome of the surgical procedure should be explained. If the procedure is being performed for diagnostic purposes, the outcome will depend on surgical or pathologic findings that are not known before surgery. When treating an anatomic deformity or disease, the expected success of the operation should be discussed, and the potential for failure of the operation (e.g., failure of tubal sterilization or the possibility that stress urinary incontinence may not be alleviated). When treating cancer, the possibility of finding more advanced disease and the potential need for adjunctive therapy (e.g., postoperative radiation therapy or chemotherapy) should be mentioned. Other issues of importance to the patient include discussion of loss of fertility or loss of ovarian function. These issues should be raised by the physician to ensure that the patient adequately understands the pathophysiology that may result from the surgery and to allow her to express her feelings regarding these emotionally charged issues. Unanticipated findings at the time of surgery should be mentioned. For example, if the ovaries are unexpectedly found to be diseased, the best surgical judgment may be that they should be removed.
4. The risks and potential complications of the surgical procedure should be discussed, including the most frequent complications of the particular surgical procedure. For most major gynecologic surgery, the risks include intraoperative and postoperative hemorrhage, postoperative infection, venous thromboembolism, injury to adjacent viscera, and wound complications. The patient should understand that minimally invasive surgery may have many of the same risks of injury or complications as does “open” surgery. Given the potential for transfusion of blood products, it should be clarified whether the patient would object to receiving a transfusion. Preexisting medical problems (e.g., diabetes, obesity, chronic obstructive pulmonary disease [COPD], coronary artery disease) result in additional risks and should be reviewed with the patient. Measures that will be taken to reduce the risk of complications should be described (e.g., prophylactic antibiotics, bowel preparation, venous thromboembolism prophylaxis).
5. The usual postoperative course should be discussed in enough detail to allow the patient to understand what to expect in the days following surgery. Information regarding the need for a suprapubic catheter, prolonged central venous monitoring, or an intensive care stay helps the patient accept her postoperative course and avoids surprises to the patient and her family that may be disconcerting. The expected duration of the recovery period, both in and out of the hospital, should be outlined.
6. Alternative methods of therapy should be discussed, including medical management or other surgical approaches. The patient should have an understanding of the outcome of the disease if nothing is done.
General Considerations
Nutrition
Young patients undergoing elective gynecologic surgery have adequate nutritional stores and, for the most part, do not require nutritional support. All patients should have a nutritional assessment, especially elderly patients and those undergoing gynecologic cancer surgery or other major gynecologic procedures in which a prolonged postoperative recovery is expected. Nutritional status should be reassessed at regular intervals postoperatively until the patient successfully returns to a regular diet.
A nutritional assessment includes a careful history and physical examination, which are the most useful, reliable, and cost-effective methods of determining a patient’s nutritional status. In particular, information about recent weight loss, dietary history, fad diets, extreme exercise, or anorexia or bulimia should be elucidated. Physical evidence of malnutrition includes temporal wasting, muscle wasting, ascites, and edema. Accurate height and weight measurements should be obtained and an ideal body weight, percentage ideal body weight, and percentage usual body weight may be calculated. Many Internet-based body weight calculators are available. A variety of techniques were developed to determine a patient’s nutritional state; however, many methods lack clinical utility outside of a research setting. Anthropometric measurements of skin-fold thickness and arm-muscle circumference provide an estimate of total body fat and lean muscle mass.
The calculated body mass index (BMI) can be used as a surrogate marker for nutritional status. The BMI is calculated as body weight in kilograms divided by the height in square centimeters. A BMI less than 22 increases the risk of malnutrition, and a BMI less than 19 gives clear evidence of malnutrition (10).
Patients who have lost less than 6% of their ideal body weight do not need preoperative nutritional intervention. However, patients who have lost more than 10% of their ideal body weight in 6 months meet the definition of severely malnourished and should be considered for preoperative intervention (11). Patients who have lost between 6% and 10% should undergo further studies to determine if preoperative intervention is needed. Laboratory assessments of albumin, transferrin, and prealbumin may be obtained in addition to the routine preoperative tests. The degree of malnutrition can in part be determined by serum concentrations of albumin, transferrin, and prealbumin. The levels of these serum proteins are greatly influenced by the patient’s level of hydration. Prealbumin has the shortest half-life, at 2 to 3 days, and levels of this protein are depressed very early in comparison with serum transferrin and albumin, which have half-lives of 8 and 20 days, respectively (12). Serum albumin is a substitute for the Prognostic Nutritional Index, which is a time-consuming calculation, in assessing malnutrition in women with gynecologic malignancies (13). A serum albumin level of 3.5 to 5.0 is in the normal range, 2.8 to 3.4 is considered to indicate mild malnutrition, 2.1 to 2.7 moderate malnutrition, and less than 2.1 severe malnutrition (14). Hypoalbuminemia is correlated with morbidity, mortality, and increased postoperative complication rates in data from the National Surgical Quality Improvement Program (15). Decisions regarding the need for nutritional support should be based on several individualized factors. These factors include the patient’s prior nutritional state, the anticipated length of time in which the patient will not be able to eat, the severity of surgery, and the likelihood of complications. The nutritional assessment should determine whether the cause of the malnutrition is increased enteral loss (malabsorption, intestinal fistula), decreased oral intake, increased nutritional requirements as a result of hypermetabolism (sepsis, malignancy), or a combination of these factors. Severe malnutrition, if not corrected, can further complicate the postoperative problem by causing altered immune function, chronic anemia, impaired wound healing, and eventually multiple organ system failure and death.
The patient’s nutritional requirements are increased by surgery for several reasons. First, there is a period following surgery during which oral intake is not allowed or is very limited. In addition, the operation itself causes increased protein catabolism, increased energy requirements, and a negative nitrogen balance. If the surgery is uncomplicated and the patient is without food for less than 7 days, this response is limited and patients usually recover without the need for nutritional support. An adequate diet is defined as providing 75% of estimated caloric and protein needs. Therefore, if an adequate oral diet is not expected for 7 to 10 days, perioperative nutritional support may be required to avoid progressive malnutrition and associated complications (14). Perioperative nutritional support reduces operative morbidity and decreases the length of hospitalization when commenced early in the postoperative course. Patients with either normal nutritional indices or mild or moderate malnutrition, who will be undergoing surgical procedures likely to require a prolonged catabolic period of more than 7 to 10 days, should have enteral or parenteral nutrition instituted in the early postoperative period as soon as the patient is hemodynamically stable. This type of management should be strongly considered in patients undergoing pelvic exenterations, urinary diversions, or multiple enterectomies (16). Preoperative nutritional support is indicated for patients who have significant preexisting malnutrition or require major elective surgery. According to the American Society for Parenteral and Enteral Nutrition (ASPEN) guidelines, evidence-based medicine supports the use of preoperative nutritional support for 7 to 14 days in moderately to severely malnourished patients undergoing major nonemergent gastrointestinal surgery (12). A Veterans Affairs Total Parenteral Nutrition Cooperative Study found that severely malnourished patients preconditioned with total parenteral nutrition (TPN) had fewer complications than did control patients, excluding infectious complications (17). In a meta-analysis review of 22 studies of preoperative TPN use, a 10% decrease in postoperative complications occurred in TPN-supported patients (18). In a prospective trial including 108 women with ovarian cancer who underwent surgical cytoreduction, 88 patients had prealbumin levels less than 18 mg/dL and 24 had prealbumin levels less than 10 mg/dL (19). All postoperative mortality (23%) and 61.5% of all complications occurred in women with prealbumin less than 10 mg/dL. Women who received preoperative TPN and had prealbumin levels that increased to greater than 10 mg/dL did not have significantly increased complications. These findings lend support to consideration of preoperative TPN or neoadjuvant chemotherapy with interval cytoreduction when the nutritional status improves. These findings are encouraging but not supported by all studies or meta-analyses (20). If preoperative TPN is prescribed, it should be tapered and stopped at midnight before surgery, restarted 24 to 72 hours after the procedure, and continued until the patient is able to meet nutritional requirements.
ASPEN guidelines do not support the routine use of nutritional support in the immediate postoperative period for patients undergoing major gastrointestinal surgery; however, the guidelines do indicate a role for nutritional support postoperatively in patients in whom oral intake will be inadequate for 7 to 10 days (12). Clinical trials demonstrate that TPN can improve nutritional status as measured by biochemical assays, immune function, and nitrogen balance. The effect of TPN on clinical outcome is less well established. Despite what seems reasonable, based on common sense and preoperative nutritional parameters, the data do not support TPN for mild to moderately malnourished patients. With severe malnutrition, preoperative TPN seems to be beneficial and should be instituted.
Route of Administration
After the decision is made that nutritional support is required, the appropriate route of administration must be determined. Enteral nutrition should be considered primarily because it is easy to deliver, associated with the fewest complications, linked to enhanced wound healing, and relatively inexpensive (21). Contraindications to this route of delivery include intestinal obstruction, gastrointestinal bleeding, and diarrhea. Many types of preparations are commercially available and can be chosen based on their caloric content, fat content, protein content, osmolality, viscosity, and price. Depending on the patient’s problem, the route of delivery may be through a Dobhoff feeding tube, a gastrostomy tube, or a feeding jejunostomy tube (22). If the gastrointestinal tract is unusable for more than 7 days postoperatively, TPN should be implemented.
Total parenteral nutrition must be delivered through a central vein and has wide acceptance as a means of providing nutritional support for surgically ill patients. It must be delivered through a subclavian or internal jugular vein, and the catheter must be placed using meticulous sterile surgical technique. Only intravenous access lines in the right atrium, superior vena cava, or inferior vena cava can be truly deemed central lines (23). Proper daily care is required to avoid infectious complications. When managed by an experienced team, the most frequent complication, infection, can be minimized (24).
Composition of Total Parenteral Nutrition Solutions
1. Calories. The daily caloric requirements can be met by providing 1,000 calories more than the patient’s basal energy expenditure. Caloric requirements can be calculated based on Long’s modification of the Harrison-Benedict formula for actual energy expenditure (AEE) (25). This is the most accurate available method to calculate an individual’s AEE:
AEE (women) = [655.10 + 9.56 Weight (kg) + 1.85 Height (cm) – 4.68 Age (yrs)] × (activity factor) × (injury factor)
Activity factor: confined to bed (1.2), out of bed (1.3).
Injury factor: minor surgery (1.2), skeletal trauma (1.3), major sepsis (1.6), severe burn (2.1).
Alternatively, daily caloric requirements can be met by giving the patient 35 kcal/kg/day for maintenance and 45 kcal/kg/day for anabolic states.
2. Protein. Daily nitrogen requirements may be met by providing 1 g of nitrogen (6.25 g of protein) for every 130 to 150 calories. Protein is provided by synthetic amino acids. The amino acids provide 15% to 20% of total calories (24).
3. Carbohydrates. The carbohydrate base of TPN is dextrose (glucose) in approximately 25% solution. Adults need approximately 100 g of dextrose per day at baseline. The maximal rate of glucose oxygenation in adults is approximately 7 g/kg/day, and glucose administration in excess of the caloric requirements can lead to fatty infiltration of the liver and other metabolic complications. When given by TPN infusion, the dextrose tolerance in critically ill patients is 5 mg/kg/min (24). Insulin should be used to maintain serum glucose concentration between 150 and 250 mg/dL, and it may be added directly to the TPN solution.
4. Fats. Lipids in a 10% to 20% emulsion can be given as further caloric supplement and supply the essential fatty acids, linoleic acid, and α-linoleic acids. More calories can be given in the form of free fatty acids, which are the major source of energy for most peripheral tissues. When lipids are used as a major source of calories, a minimum of 50 to 150 g per day of glucose should also be given to provide a substrate for the central nervous system. Most patients can tolerate up to 2 g of fat per kilogram of weight per day, and daily dosages should not exceed 4 g of fat per kilogram of weight per day. In critically ill patients, the lipid content should not exceed 1 g/kg/day. These lipid emulsions are isotonic and can be delivered simultaneously with the protein and carbohydrate mixture in a 3-L bag over a 24-hour infusion. In general, 30% to 50% of nonprotein calories should be supplied in lipid form. Serum triglyceride levels should be monitored to ensure that the patient can metabolize the fat.
5. Electrolytes, vitamins, and minerals. In addition to calories and protein, nutritional support should be maintained in terms of electrolytes, vitamins, and trace elements. Daily maintenance requirements for electrolytes are as follows: sodium, 40 to 50 mEq; potassium, 30 to 40 mEq; magnesium, 8 to 10 mEq; calcium, 2 to 5 mEq; and phosphate, 13 to 25 mmol (24). A number of vitamins and trace elements must also be supplied to ensure that the patient is eumetabolic.
Fluid and Electrolytes
Water constitutes approximately 50% to 55% of the body weight of the average woman. Two-thirds of this water is contained in the intracellular compartment. One-third is contained in the extracellular compartment, of which one-fourth is contained in plasma, and the remaining three-fourths is in the interstitium.
Osmolarity, or tonicity, is a property derived from the number of particles in a solution. Sodium and chloride are the primary electrolytes contributing to the osmolarity of the extracellular compartment. Potassium and, to a lesser extent, magnesium and phosphate are the major intracellular electrolytes. Water flows freely between the intracellular and the extracellular spaces to maintain osmotic neutrality throughout the body. Any shifts in osmolarity in any fluid spaces within the body are accompanied by corresponding shifts in free water from spaces of lower to higher osmolarity, thus maintaining equilibrium.
The average adult daily fluid maintenance requirement is approximately 30 mL/kg/day, or 2,000 to 3,000 mL per day (26). This level is offset partially by insensible losses of 1,200 mL per day, which include losses from the lungs (600 mL), skin (400 mL), and gastrointestinal tract (200 mL). Urinary output from the kidney accounts for the remainder of the fluid loss, and this output will vary depending on total body intake of water and sodium. Approximately 600 to 800 mOsm of solute are excreted by the kidneys daily. Healthy kidneys can concentrate urine up to approximately 1,200 mOsm and, therefore, the minimum output can range between 500 and 700 mL per day. The maximal urine output of the kidney can be as high as 20 L per day, as seen in patients with diabetes insipidus. In healthy individuals, the kidney adjusts output commensurate with daily fluid intake.
The major extracellular buffer used in the acid-base balance is the bicarbonate-carbonic acid system: CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3− (27). Typically, the body will maintain a bicarbonate-to-carbonic acid ratio of 20:1 to maintain an extracellular pH of 7.4. Both the lung and the kidney play integral roles in the maintenance of normal extracellular pH via retention or excretion of carbon dioxide and bicarbonate. Under conditions of alkalosis, minute ventilation decreases and renal excretion of bicarbonate increases to restore the normal ratio of bicarbonate to carbonic acid; the opposite occurs with acidosis.
Ultimately, the kidney plays the most important role in fluid and electrolyte balance through excretion and retention of water and solute. Circulating antidiuretic hormone and aldosterone help modulate the process. Serum osmolarity affects hypothalamic release of antidiuretic hormone and aldosterone secretion in response to renal perfusion. Under states of dehydration or hypovolemia, serum antidiuretic hormone levels increase, leading to increased resorption of water in the distal tubule of the kidney. Increased aldosterone release promotes increased sodium and water retention. The opposite occurs in states of fluid excess. Individuals with normal renal function and circulating antidiuretic hormone and aldosterone levels maintain normal serum osmolarity and electrolyte composition, despite daily fluctuations of fluid and electrolyte intake.
Various disease states can alter the normal fluid and electrolyte homeostatic mechanisms, making perioperative fluid and electrolyte management more difficult. Patients with intrinsic renal disease are unable to excrete solute and to maintain acid-base balance. In patients undergoing the stress of chronic starvation or severe illness, there may be an inappropriately high level of circulating antidiuretic hormone and aldosterone, resulting in fluid and sodium retention. With severe cardiac disease, secondary renal hypoperfusion can lead to increased aldosterone synthesis and increased sodium and water retention by the kidney. Patients with severe diabetes can have significant osmotic diuresis as well as acid-base dysfunction secondary to circulating keto acids. Treatment of renal, cardiac, or endocrine disorders preoperatively is imperative and often will rectify fluid and electrolyte abnormalities.
Special attention is warranted in the elderly patient undergoing surgery. Normal physiological changes associated with aging can increase the likelihood of fluid and electrolyte disorders. These changes include decreased glomerular filtration rate, decreased urinary concentrating ability, and narrowed limits for excretion of water and electrolytes (28). Fluid and electrolyte management in the perioperative period requires knowledge of the daily fluid and electrolyte requirements for maintenance, replacement of ongoing fluid and electrolyte losses, as well as correction of any existing abnormalities.
Fluid and Electrolyte Maintenance Requirements
The body adjusts to higher and lower volumes of intake by changes in plasma tonicity. Alterations in plasma tonicity induce adjustments in circulating antidiuretic hormone levels, which ultimately regulate the amount of water retained in the distal tubule of the kidney. In the preoperative and the early postoperative periods, it is usually necessary to replace only sodium and potassium. Chloride is automatically replaced, concomitant with sodium and potassium, because chloride is the usual anion used to balance sodium and potassium in electrolyte solutions. There are various commercially available solutions containing 40 mmol of sodium chloride, with smaller amounts of potassium, calcium, and magnesium, designed to meet the requirements of a patient who is receiving 3 L of intravenous fluids per day. The daily requirement can be met by any combination of intravenous fluids. For example, 2 L of D5 (5% dextrose)/0.45 normal saline (7 mEq sodium chloride each), supplemented with 20 mEq of potassium chloride, followed by 1 L of D5W (5% dextrose in water) with 20 mEq of potassium chloride, would suffice.
Fluid and Electrolyte Replacement
Fluid and electrolyte losses beyond the daily average must be replaced by appropriate solutions. The choice of solutions for replacement depends on the composition of the fluids lost. Often, it is difficult to measure free water loss, particularly in patients who have high losses from the lungs, skin, or the gastrointestinal tract. Weighing these patients daily can be very useful. Up to 300 g of weight loss daily can be attributable to weight loss from catabolism of protein and fat in the patient who is taking nothing by mouth (26). Any loss beyond this level represents fluid loss, which should be replaced accordingly.
Patients with a high fever can have increased pulmonary and skin loss of free water, sometimes in excess of 2 to 3 L per day. These losses should be replaced with free water in the form of D5W. Perspiration typically has one-third the osmolarity of plasma and can be replaced with D5W or, if the loss is excessive, with D5/0.25 normal saline.
Patients with acute blood loss need replacement with appropriate isotonic fluid or blood or both. There is a wide range of plasma volume expanders, including albumin, dextran, and hetastarch solutions, that contain large molecular weight particles (<50 kDa molecular weight). These particles are slow to exit the intravascular space, and about one-half of the particles remain after 24 hours. Controversy exists over the ideal strategy for intravascular volume replacement (29). A systematic review of 25 randomized clinical trials demonstrated preserved renal function and reduced intestinal edema in surgical patients receiving hyperoncotic albumin solutions, as compared with control fluids (30). Meta-analyses on the use of human albumin and crystalloids versus colloids in fluid resuscitation did not show a benefit in mortality rates (31,32). Caution is required in interpreting results from these pooled controlled trials because mortality outcome was not the end point of most of the studies, and publication bias is a limitation. Possible side effects with synthetic colloid solutions include adverse affects on hemostasis, severe anaphylactic reactions, and impairment of renal function (29). These solutions are expensive and for most cases, simple replacement with 0.9 normal saline or lactated Ringer’s solution will suffice. One-third of the volume of lactated Ringer’s solution or normal saline typically will remain in the intravascular space and the remainder goes to the interstitium.
Appropriate replacement of gastrointestinal fluid loss depends on the source of fluid loss in the gastrointestinal tract. Gastrointestinal secretions beyond the stomach and up to the colon are typically isotonic with plasma, with similar amounts of sodium, slightly lower amounts of chloride, slightly alkaline pH, and more potassium (in the range of 10 to 20 mEq/L). Under normal conditions, stool is hypotonic. However, under conditions of increased flow (i.e., severe diarrhea), stool contents are isotonic with a composition similar to that of the small bowel contents. Gastric contents are typically hypotonic, with one-third the sodium of plasma, increased amounts of hydrogen ion, and low pH.
In patients who have gastric outlet obstruction, nausea, and vomiting, or who undergo nasogastric suction, appropriate replacement of gastric secretions can be provided with a solution such as D5/0.45 normal saline with 20 mEq/L of potassium. Potassium supplementation is particularly important to prevent hypokalemia in these patients, whose kidneys attempt to conserve hydrogen ions in the distal tubule of the kidney in exchange for potassium ions.
In patients with bowel obstruction, 1 to 3 L of fluid can be sequestered daily in the gastrointestinal tract. This fluid should be replaced with isotonic saline or lactated Ringer’s solution. Similarly, patients with enterocutaneous fistulas or new ileostomies should receive replacement with isotonic fluids.
Correction of Existing Fluid and Electrolyte Abnormalities
Patients who have fluid or electrolyte abnormalities preoperatively can pose a diagnostic challenge. The correct diagnosis and therapy is contingent on a correct assessment of total body fluid and electrolyte status. The management of hyponatremia, for example, may be either fluid restriction or fluid replacement. The choice of treatment depends on whether there is overall extracellular fluid excess and normal body sodium stores or decreased overall total body sodium stores and extracellular fluid. A detailed history is necessary to disclose any underlying medical illness and to assess the amount and duration of any abnormal fluid losses or intake. Initial evaluation should include an assessment of hemodynamic, clinical, and urinary parameters to determine the overall level of hydration as well as the fluid status of the extracellular fluid compartment. The patient who has good skin turgor, moist mucosa, stable vital signs, and good urinary output is well hydrated. Nonpitting edema is indicative of extracellular fluid excess, whereas patients with orthostasis, sunken eyes, parched mouth, and decreased skin turgor have extracellular volume contraction. A patient’s overall extracellular fluid status does not always reflect the hydration status of the intravascular compartment. A patient can have increased interstitial fluid and yet be intravascularly dry, requiring replacement with isotonic fluid.
The laboratory workup for patients who may have preexisting fluid problems should include assessment of blood hematocrit, serum chemistry, glucose, blood urea nitrogen (BUN) and creatinine, urine osmolarity, and urine electrolyte levels. Serum osmolarity is mainly a function of the concentration of sodium and is given by the following equation:
2[Na+] + glucose (mg/dL)/18 +BUN (mg/dL)/2.8
Normal serum osmolarity is typically 290 to 300 mOsm. Blood hematocrit will rise or fall inversely at a rate of 1% per 500-mL alteration of extracellular fluid volume. The BUN:creatinine ratio is typically 10:1 but will rise to a ratio of greater than 20:1 under conditions of extracellular fluid contraction. Under conditions of extracellular fluid deficit, urine osmolarity will typically be high (>400 mOsm), whereas urine sodium concentration is low (<15 mEq/L), indicative of an attempt by the kidney to conserve sodium. Under conditions of extracellular fluid excess or in cases of renal disease in which the kidney has impaired ability to retain sodium and water, urine osmolarity will be low and urine sodium will be high (>30 mEq/L). Changes in sodium can give insight into the degree of extracellular fluid excess or deficit. In the average person, the serum sodium rises by 3 mmol/L for every liter of water deficit and falls by 3 mmol/L for each liter of water excess. One must be careful in making these estimates because patients with prolonged water and electrolyte loss can have low serum sodium levels and marked water deficits.
Specific Electrolyte Disorders
Hyponatremia
Because sodium is the major extracellular cation, shifts in serum sodium levels are usually inversely correlated with the hydration state of the extracellular fluid compartment. The pathophysiology of hyponatremia is usually expansion of body fluids leading to excess total body water (27,33). Symptomatic hyponatremia usually does not occur until the serum sodium is below 120 to 125 mEq/L. The severity of the symptoms (nausea, vomiting, lethargy, seizures) is related more to the rate of change of serum sodium than to the actual serum sodium level.
Hyponatremia in the form of extracellular fluid excess can be seen in patients with renal or cardiac failure and in conditions such as nephrotic syndrome, in which total body salt and water are increased, with a relatively greater increase in the latter. Administration of hypertonic saline to correct the hyponatremia would be inappropriate in this setting. The treatment should include, in addition to correcting the underlying disease process, water restriction with diuretic therapy. Inappropriate secretion of antidiuretic hormone (ADH) can occur with head trauma, pulmonary or cerebral tumors, and states of stress. The abnormally elevated ADH results in excess water retention. Treatment includes water restriction and, if possible, correction of the underlying cause. Demeclocycline, a tetracycline antibiotic, is effective in this disorder via its action in the kidney. The introduction of vasopressin receptor antagonists, such as tolvaptan, may replace demeclocycline as the drug of choice for the syndrome of inappropriate ADH secretion (34).
Inappropriate replacement of body salt losses with water alone will result in hyponatremia. This situation will typically occur in patients who lose large amounts of electrolytes secondary to vomiting, nasogastric suction, diarrhea, or gastrointestinal fistulas, and who received replacement with hypotonic solutions. Simple replacement with isotonic fluids and potassium will usually correct the abnormality. Rarely, rapid correction of the hyponatremia is necessary, in which case hypertonic saline (3%) can be administered. Hypertonic saline should be administered very cautiously to avoid a rapid shift in serum sodium, which will induce central nervous system dysfunction.
Hypernatremia
Hypernatremia is an uncommon condition that can be life-threatening if severe (serum sodium greater than 160 mEq/L). The pathophysiology is extracellular fluid deficit. The resultant hyperosmolar state leads to decreased water volume in cells in the central nervous system, which, if severe, can cause disorientation, seizures, intracranial bleeding, and death. The causes include excessive extrarenal water loss, which can occur in patients who have a high fever, have undergone tracheostomy in a dry environment, or have extensive thermal injuries; who have diabetes insipidus, either central or nephrogenic; and who have iatrogenic salt loading. The treatment involves correction of the underlying cause (correction of fever, humidification of the tracheostomy, administration of desmopressin for control of central diabetes insipidus) and replacement with free water either by the oral route or intravenously with D5W. As with severe hyponatremia, marked hypernatremia should be corrected slowly, no faster than 10 mEq per day, unless the patient is symptomatic from severe acute hypernatremia (35).
Hypokalemia
Hypokalemia may be encountered preoperatively in patients with significant gastrointestinal fluid loss (prolonged emesis, diarrhea, nasogastric suction, intestinal fistulas) and marked urinary potassium loss secondary to renal tubular disorders (renal tubular acidosis, acute tubular necrosis, hyperaldosteronism, prolonged diuretic use). It can arise from prolonged administration of potassium-free parenteral fluids in patients who are restricted from ingesting anything by mouth. The symptoms associated with hypokalemia include neuromuscular disturbances, ranging from muscle weakness to flaccid paralysis, and cardiovascular abnormalities, including hypotension, bradycardia, arrhythmias, and enhancement of digitalis toxicity. These symptoms rarely occur unless the serum potassium level is less than 3 mEq/L. The treatment is potassium replacement. Oral therapy is preferable in patients who are on an oral diet. If necessary, potassium replacement can be given intravenously in doses that should not exceed 10 mEq per hour.
Hyperkalemia
Hyperkalemia is encountered infrequently in preoperative patients. It is usually associated with renal impairment but can be seen in patients who have adrenal insufficiency, are taking potassium-sparing diuretics, and have marked tissue breakdown such as that occurring with crush injuries, massive gastrointestinal bleeding, or hemolysis. The clinical manifestations are mainly cardiovascular. Marked hyperkalemia (potassium >7 mEq/L) can result in bradycardia, ventricular fibrillation, and cardiac arrest. The treatment chosen depends on the severity of the hyperkalemia and whether there are associated cardiac abnormalities detected with electrocardiography. Calcium gluconate (10 mL of a 10% solution), given intravenously, can offset the toxic effects of hyperkalemia on the heart. One ampule each of sodium bicarbonate and D5W, with or without insulin, will cause a rapid shift of potassium into cells. Over the longer term, cation exchange resins such as sodium polystyrene sulfate (Kayexalate), taken orally or by enema, will bind and decrease total body potassium. Hemodialysis is reserved for emergent conditions in which other measures are not sufficient or have failed (35).
Postoperative Fluid and Electrolyte Management
Several hormonal and physiologic alterations in the postoperative period may complicate fluid and electrolyte management. The stress of surgery induces an inappropriately high level of circulating ADH. Circulating aldosterone levels are increased, especially if sustained episodes of hypotension occurred either intraoperatively or postoperatively. The elevated levels of circulating ADH and aldosterone make postoperative patients prone to sodium and water retention.
Total body fluid postoperative volume may be altered significantly. First, 1 mL of free water is released for each gram of fat or tissue that is catabolized and, in the postoperative period, several hundred milliliters of free water are released daily from tissue breakdown, particularly in the patient who has undergone extensive intra-abdominal dissection and who is restricted from ingesting food and fluids by mouth. This free water is often retained in response to the altered levels of ADH and aldosterone. Second, fluid retention is further enhanced by third spacing, or sequestration of fluid in the surgical field. The development of an ileus may result in an additional 1 to 3 L of fluid per day being sequestered in the bowel lumen, bowel wall, and peritoneal cavity.
In contrast to renal sodium homeostasis, the kidney lacks the capacity for retention of potassium. In the postoperative period, the kidneys continue to excrete a minimum of 30 to 60 mEq/L of potassium daily, irrespective of the serum potassium level and total body potassium stores (27). If this potassium is not replaced, hypokalemia may develop. Tissue damage and catabolism during the first postoperative day usually result in the release of sufficient intracellular potassium to meet the daily requirements. Beyond the first postoperative day, potassium supplementation is necessary.
Correct maintenance of fluid and electrolyte balance in the postoperative period starts with the preoperative assessment, with emphasis on establishing normal fluid and electrolyte parameters before surgery.Postoperatively, close monitoring of daily weight, urine output, serum hematocrit, serum electrolytes, and hemodynamic parameters will yield the necessary information to make correct adjustments in crystalloid replacement. The normal daily fluid and electrolyte requirements must be met and any unusual fluid and electrolyte losses, including those from the gastrointestinal tract, lungs, or skin, must be compensated. After the first few postoperative days, third-space fluid begins to return to the intravascular space, and ADH and aldosterone levels revert to normal. The excess fluid retained perioperatively is mobilized and excreted through the kidneys, and exogenous fluid requirements decrease. Patients with inadequate cardiovascular or renal reserve are prone to fluid overload during this time of third-space reabsorption, especially if intravenous fluids are not appropriately reduced.
The most common fluid and electrolyte disorder in the postoperative period is fluid overload. Fluid excess can occur concomitantly with normal or decreased serum sodium. Large amounts of isotonic fluids are usually infused intraoperatively and postoperatively to maintain blood pressure and urine output. Because the infused fluid is often isotonic with plasma, it will remain in the extracellular space. Under such conditions, serum sodium will remain within normal levels. Fluid excess with hypotonicity (decreased serum sodium) can occur if large amounts of isotonic fluid losses (e.g., blood and gastrointestinal tract) are inappropriately replaced with hypotonic fluids. The predisposition toward retention of free water in the immediate postoperative period compounds the problem. An increase in body weight occurs concomitantly with the fluid expansion. In the patient who is not allowed anything by mouth, catabolism should induce a daily weight loss as great as 300 g per day. The patient who is gaining weight in excess of 150 g per day is in a state of fluid expansion. Simple fluid restriction will correct the abnormality. When necessary, diuretics can be used to increase urinary excretion.
States of fluid dehydration are uncommon but will occur in patients who have large daily losses of fluid that are not replaced. Gastrointestinal losses should be replaced with the appropriate fluids. Patients with high fevers should be given appropriate free water replacement, because up to 2 L per day of free water can be lost through perspiration and hyperventilation. Although these increased losses are difficult to monitor, a reliable estimate can be obtained by monitoring body weight.
Postoperative Acid-Base Disorders
A variety of metabolic, respiratory, and electrolyte abnormalities in the postoperative period can result in an imbalance in normal acid-base homeostasis, leading to alkalosis or acidosis. Changes in the respiratory rate directly affect the amount of carbon dioxide that is exhaled. Respiratory acidosis will result from carbon dioxide retention in patients who have hypoventilation from central nervous system depression. This condition can result from oversedation with narcotics, particularly in the presence of concurrent severe chronic obstructive pulmonary disease. Respiratory alkalosis can result from hyperventilation caused by excitation of the central nervous system by drugs, pain, or excess ventilator support. Numerous metabolic derangements can result in metabolic alkalosis or acidosis. Proper fluid and electrolyte replacement as well as maintenance of adequate tissue perfusion will help prevent most acid-base disorders that occur during the postoperative period.
Alkalosis
The most common acid-base disorder encountered in the postoperative period is alkalosis (27). Alkalosis is usually of no clinical significance and resolves spontaneously. Several etiologic factors may include hyperventilation associated with pain; posttraumatic transient hyperaldosteronism, which results in decreased renal bicarbonate excretion; nasogastric suction, which removes hydrogen ions; infusion of bicarbonate during blood transfusions in the form of citrate, which is converted to bicarbonates; administration of exogenous alkali; and use of diuretics. Alkalosis can be corrected with removal of the inciting cause and the correction of extracellular fluid and potassium deficits (Table 22.3). Full correction usually can be safely achieved over 1 to 2 days.
Table 22.3 Causes of Metabolic Alkalosis
|
Disorder |
Source of Alkali |
Cause of Renal HCO Retention |
|
Gastric alkalosis |
||
|
Nasogastric suction |
Gastric mucosa |
↓↓ECF, ↓K |
|
Vomiting |
||
|
Renal alkalosis |
||
|
Diuretics |
Renal epithelium |
↓ECF, ↓K |
|
Respiratory acidosis and diuretics |
↓ECF, ↓K, ↑PCO2 |
|
|
Exogenous base |
NaHCO3, Na citrate, Na lactate |
Coexisting disorder of ECF, K, PaCO2 |
|
↓ECF, extracellular fluid depletion; ↓K, potassium depletion; ↑↑PCO2, carbon dioxide retention; NaHCO3, sodium bicarbonate; PaCO2, partial pressure of carbon dioxide, arterial. |
||
Marked alkalosis, with serum pH higher than 7.55, can result in serious cardiac arrhythmias or central nervous system seizures. Myocardial excitability is particularly pronounced with concurrent hypokalemia. Under such conditions, fluid and electrolyte replacement may not be sufficient to correct the alkalosis rapidly. Acetazolamide (250 to 500 mg) can be given orally or intravenously two to four times daily to induce renal bicarbonate diuresis. Treatment with an acidifying agent rarely is necessary and should be reserved for acutely symptomatic patients (i.e., those with cardiac or central nervous system dysfunction) or for patients with advanced renal disease. Under such conditions, hydrogen chloride (5 to 10 mEq per hour of a 100-mmol solution) can be given via a central intravenous line. Ammonium chloride can be given orally or intravenously but should not be given to patients with hepatic disease.
Acidosis
Metabolic acidosis is less common than alkalosis during the postoperative period, but acidosis can be serious because of its effect on the cardiovascular system. Under conditions of acidosis, there are decreased myocardial contractility, a propensity for vasodilation of the peripheral vasculature leading to hypotension, and refractoriness of the fibrillating heart to defibrillation (27). These effects promote decompensation of the cardiovascular system and can hinder attempts at resuscitation.
Metabolic acidosis results from a decrease in serum bicarbonate levels caused by the consumption and replacement of bicarbonate by circulating acids or the replacement by other anions such as chloride. The proper workup includes a measurement of the anion gap:
Anion gap = (Na+ + K+) – (CI− + HCO3−) = 10 to 14 mEq/L (normal)
The anion gap is composed of circulating protein, sulfate, phosphate, citrate, and lactate (36).
With metabolic acidosis, the anion gap can be increased or normal. An increase in circulating acids will consume and replace bicarbonate ion, increasing the anion gap. The causes include an increase in circulating lactic acid secondary to anaerobic glycolysis, such as that seen under conditions of poor tissue perfusion; increased ketoacids, as with cases of severe diabetes or starvation; exogenous toxins; and renal dysfunction, which leads to increased circulating sulfates and phosphates (37). The diagnosis can be established via a thorough history and measurement of serum lactate (normal <2 mmol/L), serum glucose, and renal function parameters. Metabolic acidosis in the face of a normal anion gap is usually the result of an imbalance of the ions chloride and bicarbonate, which occurs under conditions leading to excess chloride and decreased bicarbonate. Hyperchloremic acidosis can be seen in patients who underwent saline loading. Bicarbonate loss will be seen in patients with small bowel fistulas, new ileostomies, severe diarrhea, or renal tubular acidosis. In patients with marked extracellular volume expansion, which often occurs postoperatively, the relative decrease in serum sodium and bicarbonate will result in a mild acidosis. A summary of the various causes of metabolic acidosis is shown in Table 22.4.
Table 22.4 Causes of Metabolic Acidosis
|
High Anion Gap |
Normal Anion Gap |
|
|
Hyperkalemic |
Hypokalemic |
|
|
Uremia |
Hyporeninism |
Diarrhea |
|
Ketoacidosis |
Primary adrenal failure |
Renal tubular acidosis |
|
Lactic acidosis |
NH2Cl |
Ileal and sigmoid bladders |
|
Aspirin |
Sulfur poisoning |
Hyperalimentation |
|
Paraldehyde |
Early chronic renal failure |
|
|
Methanol |
Obstructive uropathy |
|
|
Ethylene glycol |
||
|
Methyl malonic aciduria |
||
|
NH2Cl (chloramine) |
||
|
Adapted from Narins RG, Lazarus MJ. Renal system. In: Vandam LD, ed. To make the patient ready for anesthesia: medical care of the surgical patient, 2nd ed. Menlo Park, CA: Addison Wesley, 1984:67–114. |
||
The treatment of metabolic acidosis depends on the cause. In patients with lactic acidosis, restoration of tissue perfusion is imperative. This state can be accomplished through cardiovascular and pulmonary support as needed, oxygen therapy, and aggressive treatment of systemic infection wherever appropriate. Ketosis from diabetes can be corrected gradually with insulin therapy. Ketosis resulting from chronic starvation or from lack of caloric support postoperatively can be corrected with nutrition. In patients with normal anion gap acidosis, bicarbonate lost from the gastrointestinal tract should be replaced, excess chloride administration can be curtailed, and, where necessary, a loop diuretic can be used to induce renal clearance of chloride. Dilutional acidosis can be corrected with mild fluid restriction.
Bicarbonates should not be given unless serum pH is lower than 7.2 or severe cardiac complications secondary to acidosis are present. Close monitoring of serum potassium levels is mandatory. Under states of acidosis, potassium will exit the cell and enter the circulation. The patient with a normal potassium concentration and metabolic acidosis is actually depleted of intracellular potassium. Treatment of the acidosis without potassium replacement will result in severe hypokalemia with its associated risks. A summary of the various acid-base abnormalities and associated therapies is shown in Table 22.5.
Table 22.5 Acid-Base Disorders and Their Treatment
Perioperative Pain Management
Although satisfactory analgesia is easily achievable with available methods, patients continue to suffer unnecessarily from postoperative pain. Studies consistently show that 25% to 50% of patients suffer moderate to severe pain in the postoperative period (38,39). There are several reasons for the existing inadequacies in pain management. First, patient expectations of pain relief are low and they are not aware of the extent of analgesia that they should expect. In a study of the perception of pain relief after surgery, 86% of patients had moderate to severe pain after surgery, but 70% felt that the pain was as severe as they expected (40). Second, there is a lack of formal physician training in pain management. This lack is epitomized by the commonly written order prescribing a range of narcotic to be given intramuscularly every 3 to 4 hours as needed, leaving pain management decisions to the nursing staff, with no attempt made to titrate the dose of the prescribed narcotic commensurate with individual patient requirements. Third, attitudes continue to be influenced by the common misconception that the use of narcotics in the postoperative period results in opioid dependence. In one review, 20% of nurses responding to a staff questionnaire expressed concern that the use of opioid analgesics during the postoperative period could cause addiction (40). Studies confirm that nurses administer less than one-fourth of the total dose of narcotic that is prescribed on an as-needed basis. To facilitate acute pain management and reduce the number of adverse outcomes, the American Society of Anesthesiologists established practice guidelines for acute pain management in the perioperative setting (41).
The minimal effective analgesic concentration (MEAC) refers to the serum concentration of a drug below which very little analgesia is achieved. At the MEAC, receptor and plasma concentrations of a drug are in equilibrium. Steady-state drug concentrations above the MEAC are difficult to achieve with intramuscular depot injection (42). In one study, patients receiving intramuscular injections with meperidine hydrochloride (Demerol) every 4 hours experienced marked intrapatient and interpatient variations in narcotic drug peak concentrations and in the time required to reach these peaks. As a result, serum concentrations of drug were above the MEAC an average of only 35% of each 4-hour dosing interval (43). Variable pain control following intermittent intramuscular injections is the result of inadequate, highly variable, and unpredictable blood concentrations (44). Adequate analgesia can be achieved through intramuscular or subcutaneous modes of administration, but unpredictable absorption can make titration difficult. Small intravenous boluses can be more easily titrated but may be shorter acting, requiring more frequent injections and thus intensive nursing care, whereas larger intravenous boluses may be associated with a higher incidence of central nervous system and respiratory depression. The patient-controlled analgesia (PCA) technique, which allows patients to self-administer small doses of narcotic on demand, allows titration of measured boluses of narcotic as needed to relieve pain. This technique can provide a more thorough analgesia with maintenance of steady-state drug concentrations above the MEAC.
Irrespective of the route of administration, analgesics must be front loaded to provide prompt analgesia from the start. Without front loading, attainment of the MEAC will not occur for at least three elimination half-lives of the narcotic agent that is used. After front loading, additional small boluses of narcotic can be administered until analgesia is achieved. From the total dose of drug required to achieve analgesia, maintenance drug dosages can then be determined and administered either as a continuous infusion or on a scheduled basis, so that the dose of drug administered offsets the amount that is cleared. Thereafter, prescribed doses of narcotic can be adjusted as needed.
Patient-Controlled Analgesia
Devices for administering PCA are electronically controlled infusion pumps that deliver a preset dose of narcotic into a patient’s indwelling intravenous catheter upon patient request. The devices all contain delay intervals or lockout times during which patient demands for more narcotic are not met. These devices eliminate the delay between the onset of pain and the administration of analgesic agents, a common problem inherent with on-demand analgesic orders in busy hospital wards. Patient-controlled analgesia has excellent patient acceptance. Compared with conventional intramuscular injections, serum narcotic levels have significantly lower variability in patients using PCA (42). Patients using PCA have improved analgesia, a lower incidence of postoperative pulmonary complications, and less confusion than those given intramuscular narcotics (45). The total dose of narcotic used is lower with PCA than with conventional intramuscular depot injection.
The use of PCA does not eliminate the adverse side effects of narcotics. Potentially life-threatening respiratory depression is seen in as many as 0.5% of patients using PCA. The use of a continuous narcotic infusion in addition to demand dosing is associated with a fourfold increase in respiratory depression. Elderly patients and those with preexisting respiratory compromise are at risk for respiratory depression (42).
Carefully supervised regimens using continuous infusions, on-demand intramuscular therapy, or fixed dosage schedules (every 4-hour dosing) with on-demand supplementation can have analgesic efficacy comparable with PCA. The type of close supervision required to achieve adequate on-demand analgesia without PCA is difficult to maintain. Use of PCA shortens the time between the onset of pain and the administration of pain medication, provides more continuous access to analgesics, and allows for an overall steadier state of pain control.
Epidural and Spinal Analgesia
Anesthetics and narcotics administered either in the epidural space or intrathecally are among the most potent analgesic agents available; the efficacy of these agents is greater than that provided by intravenous PCA techniques. These drugs can be administered in several ways, including a single-shot dose given by epidural or intrathecal injection, intermittent injection given either on schedule or on demand, and continuous infusion.
Because of the risk of central nervous system infections and headaches, intrathecal administration is usually limited to a single dose of narcotic, local anesthetic, or both. In comparison with epidural administration, duration of action for a single dose is increased via the intrathecal route as a result of the high concentrations of drug attained in the cerebrospinal fluid. The risk of central nervous system and respiratory depression, and systemic hypotension, is increased. The low doses of opioids required for intrathecal analgesia are sufficient to be associated with an increased risk of respiratory depression (46). Some investigators warn against the use of intrathecal spinal analgesia outside the intensive care setting.
Epidural administration is the preferred approach and provides extended (>24 hours) pain control during the postoperative period. Relative contraindications are the presence of coagulopathy, sepsis, and hypotension. Both anesthetic and narcotic agents are used with excellent efficacy. Among the anesthetic agents, bupivacaine is the most popular, providing excellent analgesia with minimal toxicity. Epidural analgesia is most suited for pain control in the lower abdomen and extremities. Potential adverse effects of epidural anesthetic agents include urinary retention, motor weakness, hypotension, and central nervous system and cardiac depression. In contrast to anesthetic agents, opioids offer excellent analgesia without accompanying sympathetic blockade. Epidural opioids tend to have a much longer duration of action, and hypotension is a rare complication. Compared with epidural anesthetics, there is a higher incidence of nausea and vomiting, respiratory depression, and pruritus (47).
Compared with analgesics administered intramuscularly or intravenously, epidural analgesia is associated with improved pulmonary function postoperatively, a lower incidence of pulmonary complications, a decrease in postoperative venous thromboembolic complications (most likely secondary to earlier ambulation), fewer gastrointestinal side effects, a lower incidence of central nervous system depression, and shorter convalescence (47). A systematic review concluded that continuous epidural anesthesia is more effective than intravenous opioid PCA in reducing postoperative pain for up to 72 hours after abdominal surgery (48). Severe respiratory depression, which occurs in less than 1% of patients, is the most serious potential complication. A lower incidence of respiratory depression occurs with the more lipophilic drugs such as fentanyl, which is quickly absorbed within the spinal cord and is less likely to diffuse to the central nervous system respiratory control centers. Pruritus, nausea, and urinary retention are common but can be managed easily and usually are of little clinical significance. Cost is perhaps the main and most limiting drawback of epidural analgesia.
Close monitoring by nursing staff is required for safe administration of epidural analgesia. An intensive care setting is not necessary. Epidural analgesics can be administered safely in a hospital ward setting under close nursing supervision, using respiratory monitoring with hourly ventilatory checks during the first 8 hours of epidural analgesia.
Nonsteroidal Anti-inflammatory Drugs
Current therapeutic strategies for perioperative pain control are largely dependent on multimodal therapy with opioid analgesics and nonsteroidal anti-inflammatory drugs (NSAIDs). The nonselective NSAID ketorolac is a potent drug that can be given orally or parenterally. Ketorolac has a slightly slower onset of activity than fentanyl but has an analgesic potency comparable to morphine. The theoretical advantages of NSAIDs over opioids include absence of respiratory depression, lack of abuse potential, decreased sedative effects, decreased nausea, early return of bowel function, and faster recovery. In clinical studies, ketorolac is found to have analgesic effects similar to those of morphine in postoperative orthopedic patients and, when used in conjunction with PCA, significantly reduced opioid requirements (49,50). Depending on the type of surgery, ketorolac has an opioid dose-sparing effect of a mean of 36% and improves analgesic control of moderate to severe pain 24 hours postoperatively (51). In the obstetric population, intravenous ketorolac is effective in reducing postoperative narcotic use after cesarean delivery (52). Although the U.S. Food and Drug Administration has not approved ketorolacfor use during lactation, it was quantified in breast milk and has lower levels than ibuprofen (53).
Potential adverse effects associated with the use of NSAIDs include an increased risk of renal compromise (particularly in patients suffering from acute hypovolemia), gastrointestinal side effects, hypersensitivity reactions, and bleeding. The effects of ketorolac on bleeding are inconsistent. Studies of ketorolac on healthy volunteers showed transient increases in bleeding time and decreases in platelet aggregation, but these changes were not clinically significant (54). A retrospective cohort study showed increased risk of gastrointestinal and operative site bleeding in elderly patients receiving high doses of ketorolac, between 105 and 120 mg per day. Increased risk for all gastrointestinal bleeding was associated with use of ketorolac for more than 5 days (55). Controlled prospective studies did not show a significant increase in blood loss in patients who receive NSAIDs perioperatively. Ketorolac may be associated with elevated rates of acute renal failure when therapy exceeds 5 days (56). A meta-analyses of the use of postoperative NSAIDs in patients with normal preoperative renal function showed a clinically insignificant reduction in renal function (57). These agents should be used with extreme care, if at all, in patients with asthma, because 5% to 10% of adult patients with asthma are sensitive to aspirin and other NSAID preparations.
With the advantages of less gastrointestinal toxicity and a lack of antiplatelet effects, selective cyclooxygenase-2 (COX-2) inhibitors are a valuable option in perioperative pain management (58). Although evidence exists showing an increased risk of serious cardiovascular events associated with COX-2 inhibitors, short-term use of these agents in the perioperative setting can be considered in low-risk patients without existing cardiovascular disease (59–64).
In addition to NSAIDs, other adjuvant analgesics are being explored to minimize opioid use and the accompanying side effects, which can delay recovery. Capsaicin is a nonnarcotic that promotes release of substance P, a neurotransmitter for pain and heat, which initially results in a burning sensation, but eventually leads to substance P depletion and a reduction in pain. It is available in both topical and injectable preparations. Ketamine blocks centrally located N-methyl-d-aspartate pain receptors, and at low subanesthetic doses can reduce central sensitization caused by surgery and prevent opioid-induced hyperalgesia. At higher doses, ketamine is associated with hallucinations, dizziness, nausea, and vomiting. Gabapentin and pregabalin are nonnarcotics that prevent the release of excitatory neurotransmitters that relay pain signals. They reduce opioid requirements and are effective antihyperalgesic agents (64).
Antimicrobial Prophylaxis in Gynecologic Surgery
Gynecologic procedures often involve breaching the reproductive and gastrointestinal tracts, which harbor endogenous bacteria capable of causing polymicrobial infections in the postoperative period (Table 22.6). Despite great advances in aseptic technique and drug development, bacterial contamination of the operative site and postoperative infections are an inevitable part of the practice of gynecologic surgery. Prevention of these surgical complications includes using proper aseptic technique, minimizing tissue trauma, minimizing the amount foreign material in the surgical site, controlling diabetes, avoiding immunologic suppression, maximizing tissue oxygenation, draining blood and serum from the surgical site, and using prophylactic antibiotics. Antibiotic prophylaxis is given with the belief that antibiotics enhance the immune mechanisms in host tissues that resist infections by killing the bacteria that inoculate the surgical site during surgery (65).
Table 22.6 Bacteria Indigenous to the Lower Genital Tract
|
Lactobacillus |
Enterobacter agglomerans |
|
Diphtheroids |
Klebsiella pneumoniae |
|
Staphylococcus aureus |
Proteus mirabilis |
|
Staphylococcus epidermidis |
Proteus vulgaris |
|
Streptococcus agalactiae |
Morganella morganii |
|
Streptococcus faecalis |
Citrobacter diversus |
|
α-Hemolytic streptococci |
Bacteroides species |
|
Group D streptococci |
B. disiens |
|
Peptostreptococci |
B. fragilis |
|
Peptococcus |
B. melaninogenicus |
|
Clostridium |
|
|
Gaffky anaerobia |
|
|
Escherichia coli |
|
|
Fusobacterium |
|
|
Enterobacter cloacae |
Infections in the skin or pelvis that result from gynecologic surgery (e.g., parametritis, cuff cellulitis, pelvic abscess) typically are polymicrobial in nature. These infections are complex and often involve gram-negative rods, gram-positive cocci, and anaerobes. Antibiotic prophylaxis should be sufficiently broad to cover these potential pathogens (66) (Table 22.7).
Table 22.7 Antibiotic Prophylaxis Regimens by Procedure
|
Procedure |
Antibiotic |
Dose |
|
Hysterectomy |
Cefazolina |
1 g or 2 g IVb |
|
Hysterosalpingogram or |
Doxycyclinee |
100 mg orally, twice daily for 5 days |
|
Induced abortion/dilation and evacuation |
Doxycycline |
100 mg orally 1 hour before procedure and 200 mg orally after procedure |
|
IV, intravenously. |
||
|
aAlternatives include cefotetan, cefoxitin, cefuroxime, or ampicillin-sulbactam. bA 2-g dose is recommended in women with a body mass index greater than 35 or weight greater than 100 kg or 220 lb. cAntimicrobial agents of choice in women with a history of immediate hypersensitivity to penicillin. dCiprofloxacin or levofloxacin or moxifloxacin. eIf patient has a history of pelvic inflammatory disease or procedure demonstrates dilated fallopian tubes. No prophylaxis is indicated for a study without dilated tubes. |
||
|
Adapted from Antibiotic prophylaxis for gynecologic procedures. American College of Obstetricians and Gynecologists Practice Bulletin No. 104, May 2009. |
||
The timing of antimicrobial prophylaxis is important. There is a relatively narrow window of opportunity for affecting outcomes (67). In the United States, it is customary to give antimicrobial prophylaxis shortly before or during the induction of anesthesia. Data revealed that a delay of 3 hours or more between the time of bacterial inoculation (i.e., skin incision) and administration of antibiotics may result in ineffective prophylaxis. Evidence indicates that for prophylaxis, one dose of antibiotic is appropriate. When the surgical procedure proceeds longer than 1 to 2 times the half-life of the drug or blood loss is greater than 1.5 L, additional intraoperative doses of antibiotics should be administered to maintain adequate levels of medication in serum and tissues (68,69). There are no data to support the continuation of prophylactic antimicrobial agents into the postoperative period for routine gynecologic procedures. For cases involving colorectal resection, a reduction in surgical site infections (SSI) was seen when antibiotics were continued for up to 24 hours. Other measures to reduce SSI incidence were taken, including tight glycemic control, maintenance of intraoperative normothermia, and placement of subcutaneous drains in obese patients (70).
Cephalosporins emerged as the most important class of antimicrobial agents for prophylaxis. These drugs have a broad spectrum and relatively low incidence of adverse reactions. Cefazolin (1 g) appears to be widely used in the United States by gynecologic surgeons because of its relatively low cost and long half-life (1.8 hours). Other cephalosporins such as cefoxitin, cefotaxime, and cefotetancommonly are used for prophylaxis. These agents appear to have a broader spectrum of activity against anaerobic bacteria and are appropriate selections when colorectal resections are possible, such as during a debulking surgery for ovarian cancer. For the majority of gynecologic procedures, there is little evidence that a clinically relevant distinction exists between cefazolin and the other agents. Morbidly obese patients, defined as having a BMI greater than 35 or weight greater than 100kg, should receive 2 g of cefazolinto achieve appropriate blood and tissue antibiotic concentrations (71).
Antimicrobial prophylaxis, although usually beneficial, is not without risk. Anaphylaxis is the most life-threatening complication from antibiotic use. Anaphylactic reactions to penicillins are reported in 0.2% courses of treatment. The fatality rate is 0.0001%. Data indicate that it is safe to administer cephalosporins to women who report a history of adverse reactions to penicillins. The incidence of adverse reactions (e.g., skin flushing, itching) in women with a history of penicillin allergy who are given cephalosporins is 1% to 10%. The incidence of anaphylaxis in this setting is less than 0.02% (72).
A single dose of broad-spectrum antibiotics can result in pseudomembranous colitis, caused by Clostridium difficile. Diarrhea may develop in as many as 15% of hospitalized patients treated with beta-lactam antibiotics (73). In patients receiving clindamycin, the rate of diarrhea is nearly 10% to 25% (74). These gastrointestinal complications from antibiotics may cause serious morbidity in the surgical patient, and the surgeon should be able to recognize and manage these problems.
Not all gynecologic surgery patients need to receive prophylactic antibiotics. The surgeon should choose agents to cover procedures based on available data, thereby avoiding the potential for adverse reactions and minimizing the unnecessary use of antibiotics, which may contribute to increased rates of antimicrobial resistance. In patients with cephalosporin allergies or anaphylaxis to penicillin, other drugs or combinations should be chosen to provide adequate prophylactic coverage. Antimicrobial prophylaxis options for common gynecologic procedures are presented in Table 22.6. Antibiotic prophylaxis is not indicated for diagnostic or operative laparoscopy, exploratory laparotomy, or diagnostic or operative hysteroscopy, including endometrial ablation, intrauterine device insertions, endometrial biopsy, or urodynamics (75).
Subacute Bacterial Endocarditis Prophylaxis
It was thought that women who had severe valvular disease or other cardiac conditions required antibiotic prophylaxis prior to genitourinary (GU) or gastrointestinal (GI) procedures in order to prevent bacterial endocarditis as a result of the transient bacteremia provoked by the surgery. After reviewing the pertinent evidence-based literature, the American Heart Association issued revised guidelines in 2007 stating that antibiotic prophylaxis was not necessary solely to prevent endocarditis in patients undergoing GI or GU procedures, including hysterectomy (Table 22.8) (76).
Table 22.8 Recommendations for Prophylaxis of Bacterial Endocarditis
|
Highest-Risk Patients |
Agents |
Regimen (within 30 – 60 min of starting procedure) |
|
Standard regimen |
Amoxicillin |
2 g PO |
|
Ampicillin |
2.0 g IM or IV |
|
|
or |
||
|
Cefazolin or ceftriaxone |
1 g IM or IV |
|
|
Cephalexin |
2 g |
|
|
Penicillin-allergic (oral) |
Cephalexin |
2 g |
|
Clindamycin |
600 mg |
|
|
Azithromycin or clarithromycin |
500 mg |
|
|
Penicillin-allergic (non-oral) |
Cefazolin or ceftriaxone |
1 g IM or IV |
|
Clindamycin |
600 mg IM or IV |
|
|
IM, intramuscularly; IV, intravenously. |
||
|
Derived from Wilson W, Taubert KA, Gewitz M, et al. Prevention of infective endocarditis: guidelines from the American Heart Association: a guideline from the American Heart Association Rheumatic Fever, Endocarditis, and Kawasaki Disease Committee, Council on Cardiovascular Disease in the Young, and the Council on Clinical Cardiology, Council on Cardiovascular Surgery and Anesthesia, and the Quality of Care and Outcomes Research Interdisciplinary Working Group. Circulation 2007;116:1736–1754 |
||
Postoperative Infections
Infections are a major source of morbidity in the postoperative period. Risk factors for infectious morbidity include the absence of perioperative antibiotic prophylaxis, contamination of the surgical field from infected tissues or from spillage of large bowel contents, an immunocompromised host, poor nutrition, chronic and debilitating severe illness, poor surgical technique, and preexisting focal or systemic infection. Sources of postoperative infection can include the lung, urinary tract, surgical site, pelvic sidewall, vaginal cuff, abdominal wound, and sites of indwelling intravenous catheters. Early identification and treatment of infection will result in the best outcome for these potentially serious complications.
Although infectious morbidity is an inevitable complication of surgery, the incidence of infections can be decreased by the appropriate use of simple preventive measures. In cases that involve transection of the large bowel, spillage of fecal contents inevitably occurs. A thorough preoperative mechanical and antibiotic bowel preparation in combination with systemic antibiotic prophylaxis will help decrease the incidence of postoperative pelvic and abdominal infections in these patients. The surgeon can further decrease the risk of postoperative infections by using meticulous surgical technique. Blood and necrotic tissue are excellent media for the growth of aerobic and anaerobic organisms. In cases in which there is higher-than-usual potential for serum and blood to collect in spaces that were contaminated by bacterial spill, closed-suction drainage may reduce the risk of infection. Antibiotic therapy, rather than prophylaxis, should be initiated during surgery in patients who have frank intra-abdominal infection or pus. Elective surgical procedures should be postponed in patients who have preoperative infections. In an epidemiologic study conducted by the Centers for Disease Control and Prevention (CDC), the incidence of nosocomial surgical infections ranged from 4.3% in community hospitals to 7% in municipal hospitals (77). Data confirmed this, with an incidence of 2% to 5% (78). Urinary tract infections accounted for approximately 40% of these nosocomial infections. Infections of the skin and wound accounted for approximately one-third of the infections, and respiratory tract infections accounted for approximately 16%. In patients who had any type of infection before surgery, the risk of infection at the surgical wound site increased fourfold. Rates of infection were higher in older patients, in patients with increased length of surgery, and in those with increased length of hospital stay before surgery. The relative risk was three times higher in patients with a community-acquired infection before surgery. These community-acquired infections included infections of the urinary and respiratory tracts.
Historically, the standard definition of febrile morbidity for surgical patients was the presence of a temperature higher than or equal to 100.4°F (38°C) on two occasions at least 4 hours apart during the postoperative period, excluding the first 24 hours. Other sources defined fever as two consecutive temperature elevations greater than 101.0°F (38.3°C) (79,80). Febrile morbidity is estimated to occur in as many as one-half of patients; it is often self-limited, resolves without therapy, and is usually noninfectious in origin (81). Overzealous evaluations of postoperative fever, especially during the early postoperative period, are time consuming, expensive, and sometimes uncomfortable for the patient (81). The value of 101.0°F is more useful than 100.4°F to distinguish an infectious cause from an inconsequential postoperative fever.
The assessment of a febrile surgical patient should include a review of the patient’s history with regard to risk factors. Both the history and the physical examination should focus on the potential sites of infection (Table 22.9). The examination should include inspection of the pharynx, a thorough pulmonary examination, percussion of the kidneys to assess for costovertebral angle tenderness, inspection and palpation of the abdominal incision, examination of sites of intravenous catheters, and an examination of the extremities for evidence of deep venous thrombosis or thrombophlebitis. In gynecologic patients, an appropriate workup may include inspection and palpation of the vaginal cuff for signs of induration, tenderness, or purulent drainage. A pelvic examination should be performed to identify a mass consistent with a pelvic hematoma or abscess and to look for signs of pelvic cellulitis.
Table 22.9 Posthysterectomy Infections
|
Operative Site |
Nonoperative Site |
|
Vaginal cuff |
Urinary tract |
|
Pelvic cellulitis |
Asymptomatic bacteriuria |
|
Pelvic abscess |
Cystitis |
|
Supervaginal, extraperitoneal |
Pyelonephritis |
|
Intraperitoneal |
Respiratory |
|
Adnexa |
Atelectasis |
|
Cellulitis |
Pneumonia |
|
Abscess |
Vascular |
|
Abdominal incision |
Phlebitis |
|
Cellulitis |
Septic pelvic thrombophlebitis |
|
Simple |
|
|
Progressive bacterial synergistic |
|
|
Necrotizing fasciitis |
|
|
Myonecrosis |
Patients with fever in the early postoperative period should have an aggressive pulmonary toilet, including incentive spirometry (80). If the fever persists beyond 72 hours postoperatively, additional laboratory and radiologic data may be obtained. The evaluation may include complete and differential white blood cell counts and a urinalysis. In one study, results from fever workups included positive blood cultures in 9.7% of patients, a positive urine culture in 18.8%, and a positive chest x-ray in 14%. These data support the need for a tailored workup based on the patient’s clinical picture (82). Blood cultures can be obtained but will most likely be of little yield unless the patient has a high fever (102°F). In patients with costovertebral angle tenderness, intravenous pyelogram may be indicated to rule out the presence of ureteral damage or obstruction from surgery, particularly in the absence of laboratory evidence of urinary tract infection. Patients who have persistent fevers without a clear localizing source should undergo CT scanning of the abdomen and pelvis to rule out the presence of an intra-abdominal abscess. If fever persists in patients who had gastrointestinal surgery, a barium enema or upper gastrointestinal studies with small bowel assessment may be indicated late in the course of the first postoperative week to rule out an anastomotic leak or fistula.
Urinary Tract Infections
Historically, the urinary tract was the most common site of infection in surgical patients (83). The incidence reported in the gynecologic literature is less than 4% (84,85). This decrease in urinary tract infections is most likely the result of increased perioperative use of prophylactic antibiotics. The incidence of postoperative urinary tract infection in gynecologic surgical patients not receiving prophylactic antibiotics is confirmed to be as high as 40%, and even a single dose of perioperative prophylactic antibiotic decreases the incidence of postoperative urinary tract infection to as low as 4% (86,87).
Symptoms of a urinary tract infection may include urinary frequency, urgency, and dysuria. In patients with pyelonephritis, other symptoms include headache, malaise, nausea, and vomiting. A urinary tract infection is diagnosed on the basis of microbiology and is defined as the growth of 105 organisms per milliliter of urine cultured. Most infections are caused by coliform bacteria, with Escherichia coli being the most frequent pathogen. Other pathogens include Klebsiella, Proteus, and Enterobacter species. Staphylococcus organisms are the causative bacteria in fewer than 10% of cases.
Despite the high incidence of urinary tract infections in the postoperative period, few of these infections are serious. Most are confined to the lower urinary tract, and pyelonephritis is a rare complication (88). Catheterization of the urinary tract, either intermittently or continuously with the use of an indwelling catheter, is implicated as a main cause of urinary tract contamination (89). More than 1 million catheter-associated urinary tract infections occur yearly in the United States, and catheter-associated bacteria remains the most common etiology of gram-negative bacteremia in hospitalized patients. Bacteria adhere to the surface of urinary catheters and grow within bile films, which appear to protect embedded bacteria from antibiotics, making treatment less effective. The use of urinary tract catheters should be minimized. An indwelling catheter should be removed or replaced in a patient undergoing treatment for catheter-related infections.
The treatment of urinary tract infection includes hydration and antibiotic therapy. Commonly prescribed and effective antibiotics include penicillin, sulfonamides, cephalosporins, fluoroquinolones, and nitrofurantoin. The choice of antibiotic should be based on knowledge of the susceptibility of organisms cultured at a particular institution. In some institutions, for example, more than 40% of E. coli strains are resistant to ampicillin. For uncomplicated urinary tract infections, an antibiotic that has good activity against E. coli should be given in the interim while awaiting results of the urine culture and sensitivity data.
Patients who have a history of recurrent urinary tract infections, those with chronic indwelling catheters (Foley catheters or ureteral stents), and those who have urinary conduits should be treated with antibiotics that will be effective against the less common urinary pathogens such as Klebsiella and Pseudomonas. Chronic use of fluoroquinolones for prophylaxis is not advised because these agents are notorious for inducing antibiotic-resistant strains of bacteria.
Pulmonary Infections
The respiratory tract is an uncommon site for infectious complications in gynecologic surgical patients. In one study only six cases of pneumonia occurred in more than 4,000 women who underwent elective hysterectomy (85). This low incidence is probably a reflection of the young age and good health status of gynecologic patients in general. In acute care facilities, pneumonia is a frequent hospital-acquired infection, particularly in elderly patients (90). Risk factors include extensive or prolonged atelectasis, preexistent COPD, severe or debilitating illness, central neurologic disease causing an inability to clear oropharyngeal secretions effectively, nasogastric suction, and a prior history of pneumonia (90,91). In surgical patients, early ambulation and aggressive management of atelectasis are the most important preventive measures. The role of prophylactic antibiotics remains unclear.
A significant percentage (40% to 50%) of cases of hospital-acquired pneumonia is caused by gram-negative organisms (83). These organisms gain access to the respiratory tract from the oral pharynx. Gram-negative colonization of the oral pharynx is increased in patients in acute care facilities and is associated with the presence of nasogastric tubes, preexisting respiratory disease, mechanical ventilation, and tracheal intubation (92). The use of antimicrobial drugs seems to significantly increase the frequency of colonization of the oral pharynx with gram-negative bacteria.
A thorough lung examination should be included in the assessment of all febrile surgical patients. In the absence of significant lung findings, chest radiography is probably of little benefit in patients at low risk for postoperative pulmonary complications. In patients with pulmonary findings or with risk factors for pulmonary complications, chest radiography should be performed. A sputum sample should be obtained for Gram stain and culture. The treatment should include postural drainage, aggressive pulmonary toilet, and antibiotics. The antibiotic chosen should be effective against both gram-positive and gram-negative organisms. In patients who are receiving assisted ventilation, the antibiotic spectrum should include drugs that are active against Pseudomonas organisms.
Phlebitis
Historically, intravenous catheter–related infections were common; the reported incidence is 25% to 35% in the 1980s (93). Because the incidence of catheter-related phlebitis increases significantly after 72 hours, intravenous catheters should be changed at least every 3 days according to the CDC (94). The institution of intravenous therapy teams decreased the incidence of phlebitis by as much as 50% in one study (95). In combination, these measures led to a dramatic decrease in peripheral catheter site infection.
The intravenous site should be inspected daily, and the catheter should be removed if there is any associated pain, redness, or induration. Phlebitis can occur even with close surveillance of the intravenous site. In one study, more than 50% of the cases of phlebitis became evident more than 12 hours after discontinuation of intravenous catheters (96). Less than one-third of patients had symptoms related to the intravenous catheter site 24 hours before the diagnosis of phlebitis.
Phlebitis can be diagnosed based on the presence of fever, pain, redness, induration, or a palpable venous cord. Occasionally, suppuration will be present. Phlebitis is usually self-limited and resolves within 3 to 4 days. The treatment includes application of warm, moist compresses and prompt removal of any catheters from the infected vein. Antibiotic therapy with antistaphylococcal agents should be instituted for catheter-related sepsis. Excision or drainage of an infected vein rarely is necessary.
Wound Infections
The results of a prospective study of more than 62,000 wounds were revealing in regard to the epidemiology of wound infections (97). The wound infection rate varied markedly, depending on the extent of contamination of the surgical field. The wound infection rate for clean surgical cases (infection not present in the surgical field, no break in aseptic technique, no viscus entered) was lower than 2%, whereas the incidence of wound infections with dirty, infected cases was 40% or higher. Preoperative showers with hexachlorophene slightly lowered the infection rate for clean wounds, whereas preoperative shaving of the wound site with a razor increased the infection rate. A 5-minute wound preparation immediately before surgery was as effective as preparation for 10 minutes. The wound infection rate increased with the duration of preoperative hospital stay and with the duration of surgery. Incidental appendectomy increased the risk of wound infection in patients undergoing clean surgical procedures. The study concluded that the incidence of wound infections could be decreased by short preoperative hospital stays, hexachlorophene showers before surgery, minimizing shaving of the wound site, use of meticulous surgical technique, decreasing operative time as much as possible, bringing drains out through sites other than the wound, and dissemination of information to surgeons regarding their wound infection rates. A program instituting these conclusions led to a decrease in the clean wound infection rate from 2.5% to 0.6% over an 8-year period. The wound infection rate in most gynecologic services is lower than 5%, reflective of the clean nature of most gynecologic operations.
The symptoms of wound infection often occur late in the postoperative period, usually after the fourth postoperative day, and may include fever, erythema, tenderness, induration, and purulent drainage. Wound infections that occur on postoperative days 1 through 3 are generally caused by streptococcal and Clostridia infections. The management of wound infections is mostly mechanical and involves opening the infected portion of the wound above the fascia, with cleansing and debridement of the wound edges as necessary. Wound care, consisting of debridement and dressing changes two to three times daily with mesh gauze, will promote growth of granulation tissue, with gradual filling in of the wound defect by secondary intention. Clean, granulating wounds can often be secondarily closed with good success, shortening the time required for complete wound healing.
The technique of delayed primary wound closure can be used in contaminated surgical cases to lower the incidence of wound infection. This technique involves leaving the wound open above the fascia at the time of the initial surgical procedure. Vertical interrupted mattress sutures through the skin and subcutaneous layers are placed 3 cm apart but are not tied. Wound care is instituted immediately after surgery and continued until the wound is noted to be granulating well. Sutures may then be tied and the skin edges further approximated using sutures or staples. Using this technique of delayed primary wound closure, the overall wound infection rate is decreased from 23% to 2.1% in high-risk patients (98).
Pelvic Cellulitis
Vaginal cuff cellulitis is present in most patients who underwent hysterectomy. It is characterized by erythema, induration, and tenderness at the vaginal cuff. A purulent discharge from the apex of the vagina may be present. The cellulitis is often self-limited and does not require any treatment. Fever, leukocytosis, and pain localized to the pelvis may accompany severe cuff cellulitis and most often signifies extension of the cellulitis to adjacent pelvic tissues. In such cases, broad-spectrum antibiotic therapy should be instituted with coverage for gram-negative, gram-positive, and anaerobic organisms. If purulence at the vaginal cuff is excessive or if there is a fluctuant mass noted at the vaginal cuff, the vaginal cuff should be gently probed and opened with a blunt instrument. The cuff can be left open for dependent drainage or, alternatively, a drain can be placed into the lower pelvis through the cuff and removed when drainage, fever, and symptoms in the lower pelvic region have resolved.
Intra-abdominal and Pelvic Abscess
The development of an abscess in the surgical field or elsewhere in the abdominal cavity is an uncommon complication after a gynecologic surgery. It is likely to occur in contaminated cases in which the surgical site is not adequately drained or as a secondary complication of hematomas. The causative pathogens in patients who have intra-abdominal abscesses are usually polymicrobial in nature. The aerobes most commonly identified include E. coli, Klebsiella, Streptococcus, Proteus, and Enterobacter. Anaerobic isolates are common, usually from the Bacteroides group. These pathogens arise mainly from the vaginal tract but can be derived from the gastrointestinal tract, particularly when the colon was entered at the time of surgery.
Intra-abdominal abscess is sometimes difficult to diagnose. The evolving clinical picture is often one of persistent febrile episodes with a rising white blood cell count. Findings on abdominal examination may be equivocal. If an abscess is located deep in the pelvis, it may be palpable by pelvic or rectal examination. For abscesses above the pelvis, the diagnosis will depend on radiologic confirmation.
Ultrasonography can occasionally delineate fluid collections in the upper abdomen and in the pelvis. Bowel gas interference makes visualization of fluid collections or abscesses in the midabdomen difficult to distinguish. Computed tomography scanning is more sensitive and specific for diagnosing intra-abdominal abscesses and often is the radiologic procedure of choice. Occasionally, if conventional radiologic methods fail to identify an abscess and the index of suspicion for an abscess remains high, labeled leukocyte scanning may be useful for locating the infected focus.
Standard therapy for intra-abdominal abscess is evacuation and drainage combined with appropriate parenteral administration of antibiotics. Abscesses located low in the pelvis, particularly in the area of the vaginal cuff, can be reached through a vaginal approach. In many patients, the ability to drain an abscess by placement of a drain percutaneously under CT guidance obviated the need for surgical exploration. With CT guidance, a pigtail catheter is placed into an abscess cavity via transperineal, transrectal, or transvaginal approaches. The catheter is left in place until drainage decreases. Transperineal and transrectal drainage of deep pelvic abscesses is successful in 90% to 93% of patients, obviating the need for surgical management (99,100). For those patients in whom radiologic drainage is not successful, surgical exploration and evacuation are indicated. The standard approach to initial antibiotic therapy is the combination of ampicillin, gentamicin, and clindamycin. Adequate treatment can be achieved with available broad-spectrum single agents (including the broad-spectrum penicillin), second- and third-generation cephalosporins, levofloxacin and metronidazole, and the sulbactam-clavulanic acid–containing preparations (101).
Necrotizing Fasciitis
Necrotizing fasciitis is an uncommon infectious disorder, affecting roughly 1,000 patients per year (102). This disease process is characterized by a rapidly progressive bacterial infection that involves the subcutaneous tissues and fascia while characteristically sparing underlying muscle. Systemic toxicity is a frequent feature of this disease, as manifested by the presence of dehydration, septic shock, disseminated intravascular coagulation, and multiple organ system failure.
The pathogenesis of necrotizing fasciitis involves a polymicrobial infection of the dermis and subcutaneous tissue. Hemolytic streptococcus was initially believed to be the primary pathogen responsible for the infection in necrotizing fasciitis (103). Other organisms are often cultured in addition to streptococcus, including other gram-positive organisms, coliforms, and anaerobes (104). Bacterial enzymes such as hyaluronidase and lipase released in the subcutaneous space destroy the fascia and adipose tissue and induce a liquefactive necrosis. Noninflammatory intravascular coagulation or thrombosis subsequently occurs. Intravascular coagulation results in ischemia and necrosis of the subcutaneous tissues and skin. Subcutaneous spread of up to 1 inch per hour can be seen, often with little effect on the overlying skin (104). Late in the course of the infection, destruction of the superficial nerves produces anesthesia in the involved skin. The release of bacteria and bacterial toxins into the systemic circulation can cause septic shock, acid-base disturbances, and multiple organ impairment.
The diagnosis is often difficult to make early in the disease course. Most patients with necrotizing fasciitis develop erythema, edema, and pain, which in the early stages of the disease is disproportionately greater than that expected from the degree of cellulitis present and characteristically extends beyond the border of erythema (105). Late in the course of the infection, the involved skin may be anesthetized secondary to necrosis of superficial nerves. Temperature abnormalities, both hyperthermia and hypothermia, are concomitant with the release of bacterial toxins and with bacterial sepsis (104). The involved skin is initially tender, erythematous, and warm. Edema develops, and the erythema spreads diffusely, fading into normal skin, characteristically without distinct margins or induration. Subcutaneous microvascular thrombosis induces ischemia in the skin, which becomes cyanotic and blistered. As necrosis develops, the skin becomes gangrenous and may slough spontaneously (104). Most patients will have leukocytosis and acid-base abnormalities. Subcutaneous gas may develop, which can be identified by palpation and by radiography. The finding of subcutaneous gas by radiography is often indicative of clostridial infection, although it is not a specific finding and may be caused by other organisms. These organisms include Enterobacter, Pseudomonas, anaerobic streptococci, and Bacteroides, which, unlike clostridial infections, spare the muscles underlying the affected area. A tissue biopsy specimen for Gram stain and aerobic and anaerobic culture should be obtained from the necrotic center of the lesion to identify the etiologic organisms (105). Although necrotizing fasciitis often is diagnosed during surgery, a high index of suspicion and liberal use of frozen-section biopsy can provide an early life-saving diagnosis and minimize morbidity (104).
Predisposing risk factors for necrotizing fasciitis include diabetes mellitus, alcoholism, an immunocompromised state, hypertension, peripheral vascular disease, intravenous drug abuse, and obesity (104). The most frequent site of infection is in the extremities, but the infection can occur anywhere in the subcutaneous tissues, including the head and neck, trunk, and perineum. Necrotizing fasciitis occurs after trauma, surgery, burns, and lacerations; as a secondary complication in perirectal infections or Bartholin duct abscesses; and de novo (103,106–109). Increased age, delay in diagnosis, inadequate debridement during initial surgery, extensive disease at the time of diagnosis, and the presence of diabetes mellitus are all factors that are associated with an increased likelihood of mortality from necrotizing fasciitis (104–106). Early diagnosis and aggressive management of this lethal disease contribute to improved survival.
Successful management of necrotizing fasciitis involves early recognition, immediate initiation of resuscitative measures (including correction of fluid, acid-base, electrolyte, and hematologic abnormalities), aggressive surgical debridement and redebridement as necessary, and broad-spectrum intravenous antibiotic therapy (104). During surgery, the incision should be made through the infected tissue down to the fascia. An ability to undermine the skin and subcutaneous tissues with digital palpation often will confirm the diagnosis. Multiple incisions can be made sequentially toward the periphery of the affected tissue until well-vascularized, healthy, resistant tissue is reached at all margins. The remaining affected tissue must be excised. The wound can be packed and sequentially debrided on a daily basis as necessary until healthy tissue is displayed at all margins. Hyperbaric oxygen therapy may be of some benefit, particularly in patients for whom culture results are positive for anaerobic organisms (110). Retrospective nonrandomized studies demonstrated that the addition of hyperbaric oxygen therapy to surgical debridement and antimicrobial therapy appears to significantly decrease both wound morbidity and overall mortality in patients with necrotizing fasciitis (110). The benefit of hyperbaric therapy demonstrated in one study was remarkable, given that patients receiving hyperbaric oxygen were sicker and had a higher incidence of diabetes mellitus, leukocytosis, and shock (106).
After the initial resuscitative efforts and surgical debridement, the primary concern is the management of the open wound. Allograft and xenograft skin can be used to cover open wounds, thus decreasing heat and evaporative water loss. Temporary biologic closure of open wounds seems to decrease bacterial growth (111). Amniotic membranes were effective wound covering in patients with necrotizing fasciitis (112).
A new technology demonstrated to significantly improve wound healing in laboratory and clinical studies is a vacuum-assisted closure (VAC) method that uses a subatmospheric pressure technique (113–115). In situations in which spontaneous closure is not likely, the VAC device may allow for the development of a suitable granulation bed and prepare the tissue for graft placement, thereby increasing the probability of graft survival. Skin flaps can be mobilized to help cover open wounds when the infections resolve and granulation begins.
Gastrointestinal Preparation
Traditionally, mechanical bowel preparation was advised before abdominal surgery, especially if colonic surgery was anticipated. Despite the infrequent need for colonic surgery (or injury) when performing gynecologic surgery, bowel preparation is part of the standard practice for many gynecologists. Advantages of mechanical bowel preparation include reduction of gastrointestinal contents, which facilitates the surgical procedure by allowing more room in the abdomen and pelvis. If a rectosigmoid colon enterotomy occurs, the mechanical bowel preparation eliminates formed stool and reduces the risk of bacterial contamination, thus reducing infectious complications.
Randomized clinical trials questioned the need for mechanical bowel preparation in colonic surgery (116). Although somewhat controversial, a meta-analyses including almost 5,000 patients showed no statistical difference between the groups for anastomotic leakage (p = 0.46), pelvic or abdominal abscess (p = 0.75), and wound sepsis (p = 0.11). The use of different mechanical regimes did not influence primary and secondary outcomes. The authors concluded that this analysis demonstrates that any kind of mechanical bowel preparation should be omitted before colonic surgery. The main limitation concerned rectal surgery for which the limited data preclude any interpretation.
A randomized trial of mechanical bowel preparation versus no bowel preparation with rectal surgery found that the overall and site-specific infectious morbidity rates were significantly higher in no preparation versus the mechanical preparation group. Regarding anastomotic leakage, length of hospital stay, major morbidity and mortality rates, there was no significant difference between the no preparation and mechanical bowel preparation groups. This was the first randomized trial to demonstrate that rectal cancer surgery without mechanical preparation is associated with higher risk of overall and infectious morbidity rates without any significant increase of anastomotic leakage rate. It suggests continuing to perform mechanical preparation before elective rectal resection for cancer (117).
Despite evidence of the infectious complications associated with mechanical preparation or no preparation, many gynecologic surgeons prefer a mechanical preparation to aid with exposure in the pelvic operative field. This may be particularly relevant to the surgeon performing minimally invasive surgery.
Mechanical bowel preparation may be accomplished as presented in (Table 22.10) The traditional use of laxatives and enemas requires at least 12 to 24 hours and causes moderate abdominal distention and crampy pain. Randomized trials comparing traditional mechanical bowel preparation (magnesium citrate and enemas) with oral gut lavage (PEG electrolyte solution, GoLYTELY) found that the use of approximately 4 L of GoLYTELY (administered until the rectal effluent is clear) provides more complete, faster, and more comfortable bowel preparation (118). However, the ingestion of 4 L of fluid is problematic for many patients, so magnesium citrate may be preferable when mechanical preparation is to be used.
Table 22.10 Mechanical Bowel Preparation
|
Preoperative Day 1 Clear liquid diet |
|
Mechanical Prep |
|
4 L of GoLYTELY |
|
Antibiotic Prep (Optional) |
|
Neomycin (oral), 1 g every 4 h for three doses (4, 8, 12 p.m.) |
|
aBe aware of acute phosphate nephropathy. Avoid use of phospho-soda in patients with inadequate hydration, increased age, a history of hypertension, current use of an angiotensin receptor blocker, or angiotensin-conversing enzyme (ACE) inhibitors; renal disease or chronic heart failure and those taking nonsteroidal anti-inflammatory drugs (NSAIDs) or diuretics. |
An alternative mechanical preparation method is the use of oral sodium phosphate (Phospho-Soda). When evaluated in a randomized trial comparing the 4 L of GoLYTELY with oral sodium phosphate, colonoscopic examination disclosed that both methods were equally effective in colonic cleansing, and more patients preferred the sodium phosphate method (119). Some patients are at higher risk to develop acute phosphate nephropathy, leading to acute renal failure or worsening of chronic renal disease after the use of sodium phosphate. Although the pathophysiology is not fully understood, it may be secondary to substantial fluid shifts and electrolyte changes. It is speculated that potential etiologic factors included inadequate hydration, increased patient age, a history of hypertension, and current use of an angiotensin receptor blocker or angiotension-converting enzyme (ACE) inhibitors. Patients with chronic renal disease or chronic heart failure and those taking NSAIDs or diuretics appear to be at higher risk of acute phosphate nephropathy (120). For these patients, the guidelines recommend an alternative bowel preparation agent, polyethylene glycol, which is not associated with volume shifts and electrolyte abnormalities (121,122).
Oral antibiotic prophylaxis was advised over the past three decades to reduce the infectious complications following colonic surgery. The usual regimen was a combination of oral erythromycin and neomycintaken the day before surgery. Many surgeons would substitute oral metronidazole for erythromycin because patients tolerate it better. With the use of perioperative parental antibiotics, the benefit of oral antibiotics is questioned and most surgeons abandoned the use of oral antibiotics in favor of perioperative parenteral antibiotics.
Postoperative Gastrointestinal Complications
Ileus
Following open abdominal or pelvic surgery, most patients experience some degree of intestinal ileus. The exact mechanism by which this arrest and disorganization of gastrointestinal motility occurs is unknown, but it appears to be associated with the opening of the peritoneal cavity and is aggravated by manipulation of the intestinal tract and prolonged surgical procedures. Infection, peritonitis, and electrolyte disturbances may result in ileus. For most patients undergoing common gynecologic operations, the degree of ileus is minimal, and gastrointestinal function returns relatively rapidly, allowing the resumption of oral intake within a few days of surgery. Patients who have persistently diminished bowel sounds, abdominal distention, and nausea and vomiting require further evaluation and more aggressive management. Patients with symptoms of ileus or small bowel obstruction who underwent minimally invasive surgery are a different matter. Minimally invasive surgery should result in a daily improvement in GI function. An “ileus” in the case of minimally invasive surgery more likely represents GI injury, which should be evaluated immediately with a CT scan using GI contrast.
Ileus is usually manifested by abdominal distention and should be evaluated by physical examination. Pertinent points of the abdominal examination include assessment of the quality of bowel sounds and palpation in search of distension, masses, tenderness, or rebound. The possibility that the patient’s signs and symptoms may be associated with a more serious intestinal obstruction or intestinal complication (such as a perforation) must be considered. Pelvic examination should be performed to evaluate the possibility of a pelvic abscess or hematoma that may contribute to the ileus. Abdominal radiography to evaluate the abdomen in the flat (supine) position and in the upright position will aid in the diagnosis of an ileus. The most common radiographic findings include dilated loops of small and large bowel and air-fluid levels while the patient is in the upright position. Sometimes, massive dilation of the colon or stomach may be noted. The remote possibility of distal colonic obstruction suggested by a dilated cecum should be excluded by rectal examination, proctosigmoidoscopy, colonoscopy, or barium enema. In the postoperative gynecology patient, especially in the upright position, the abdominal x-ray may show free air. This common finding following surgery lasts 7 to 10 days in some instances and is not indicative of a perforated viscus in most patients.
The initial management of a postoperative ileus is aimed at gastrointestinal tract decompression and maintenance of appropriate intravenous replacement fluids and electrolytes.
1. The patient should be made NPO status (nothing by mouth) with intravenous (IV) fluids and electrolytes. If nausea and vomiting persist, a nasogastric tube should be used to evacuate the stomach of its fluid and gaseous contents. Continued nasogastric suction removes swallowed air, which is the most common source of gas in the small bowel.
2. Fluid and electrolyte replacement must be adequate to keep the patient well hydrated and in metabolic balance. Significant amounts of third-space fluid loss occur in the bowel wall, the bowel lumen, and the peritoneal cavity during the acute episode. Gastrointestinal fluid losses from the stomach may lead to metabolic alkalosis and depletion of other electrolytes as well. Careful monitoring of serum chemistry levels and appropriate replacement are necessary.
3. Most cases of severe ileus begin to improve over a period of several days. This improvement is recognizable by a reduction in the abdominal distention, return of normal bowel sounds, and passage of flatus or stool. Repeat abdominal radiographs should be obtained as necessary for further monitoring.
4. When the gastrointestinal tract function appears to have returned to normal, the nasogastric tube may be removed and a liquid diet instituted.
5. If a patient shows no evidence of improvement during the first 48 to 72 hours of medical management, other causes of ileus should be sought. Such cases may include ureteral injury, peritonitis from pelvic infection, unrecognized gastrointestinal tract injury with peritoneal spill, or fluid and electrolyte abnormalities such as hypokalemia. With persistent ileus, the use of water-soluble upper gastrointestinal contrast studies (CT scan with oral contrast) may assist in the resolution, but prospective randomized data regarding this maneuver are lacking.
Small Bowel Obstruction
Obstruction of the small bowel following major gynecologic surgery occurs in approximately 1% to 2% of patients (123). The most common cause of small bowel obstruction is adhesions to the operative site. If the small bowel becomes adherent in a twisted position, partial or complete obstruction may result from distention, ileus, or bowel wall edema. Less common causes of postoperative small bowel obstruction include entrapment of the small bowel into an incisional hernia and an unrecognized defect in the small bowel or large bowel mesentery. Early in its clinical course, a postoperative small bowel obstruction may exhibit signs and symptoms identical to those of ileus. Initial conservative management as outlined for the treatment of ileus is appropriate. Because of the potential for mesenteric vascular occlusion and resulting ischemia or perforation, worsening symptoms of abdominal pain, progressive distention, fever, leukocytosis, or acidosis should be evaluated carefully because immediate surgery may be required.
In most cases of small bowel obstruction following gynecologic surgery, the obstruction is only partial and the symptoms usually resolve with conservative management.
1. Further evaluation after several days of conservative management may be necessary. Evaluation of the gastrointestinal tract with barium enema, an upper gastrointestinal study, or a CT scan with small bowel assessment is appropriate. In most cases, complete obstruction is not documented, although a narrowing (“transition point”) or tethering of the segment of small bowel may indicate the site of the problem.
2. Further conservative management with nasogastric decompression and intravenous fluid replacement may allow time for bowel wall edema or torsion of the mesentery to resolve.
3. If resolution is prolonged and the patient’s nutritional status is marginal, the use of TPN may be necessary.
4. Conservative medical management of postoperative small bowel obstruction usually results in complete resolution. If persistent evidence of small bowel obstruction remains after full evaluation and an adequate trial of medical management, exploratory laparotomy may be necessary to manage the obstruction. In most cases, lysis of adhesions is all that is required, although a segment of small bowel that is badly damaged or extensively sclerosed from adhesions may require resection and reanastomosis.
Colonic Obstruction
Postoperative colonic obstruction following surgery for most gynecologic conditions is exceedingly rare. It is associated with a pelvic malignancy, which in most cases was known at the time of the initial operation. Advanced ovarian carcinoma is the most common cause of colonic obstruction in postoperative gynecologic surgery patients, and it is caused by extrinsic impingement on the colon by the pelvic malignancy. Intrinsic colonic lesions may be undetected, especially in a patient with some other benign gynecologic condition. When colonic obstruction is manifested by abdominal distention and abdominal radiography reveals a dilated colon and enlarging cecum, further evaluation of the large bowel is required by barium enema or colonoscopy. Dilation of the cecum to more than 10 to 12 cm in diameter as viewed by abdominal radiography requires immediate evaluation and surgical decompression by performing colectomy or colostomy. Surgery should be performed as soon as the obstruction is documented. Conservative management of colonic obstruction is not appropriate because the complication of colonic perforation has an exceedingly high mortality rate. In patients who are too ill to undergo surgery, the interventional radiologist may be able to place a cecostomy tube or the gastroenterologist may place a colonic stent (124).
Diarrhea
Episodes of diarrhea often occur following abdominal and pelvic surgery as the gastrointestinal tract returns to its normal function and motility. Prolonged and multiple episodes may represent a pathologic process such as impending small bowel obstruction, colonic obstruction, or pseudomembranous colitis. Excessive amounts of diarrhea should be evaluated by abdominal radiography and stool samples tested for the presence of ova and parasites, bacterial culture, and Clostridium difficile toxin. Proctoscopy and colonoscopy may be advisable in severe cases. Evidence of intestinal obstruction should be managed as outlined previously. Infectious causes of diarrhea should be managed with the appropriate antibiotics and fluid and electrolyte replacement. C. difficile–associated pseudomembranous colitis may result from exposure to any antibiotic. Discontinuation of these antibiotics (unless they are needed to treat another severe infection) is advisable, along with the institution of appropriate therapy. Oral metronidazole is a suitable agent for instituting therapy and is less expensive than vancomycin. Therapy should be continued until the diarrhea abates, and several weeks of oral therapy may be required to obtain complete resolution of the pseudomembranous colitis.
Fistula
Gastrointestinal fistulas are relatively rare following gynecologic surgery. They are most often associated with malignancy, prior radiation therapy, intestinal resection with anastomosis, or surgical injury to the large or small bowel that was improperly repaired or unrecognized. Signs and symptoms of gastrointestinal fistula are often similar to those of small bowel obstruction or ileus, except that fever is usually a more prominent component of the patient’s symptoms. When fever is associated with gastrointestinal dysfunction postoperatively, evaluation should include early assessment of the gastrointestinal tract to confirm its continuity. When fistula is suspected, the use of water-soluble gastrointestinal contrast material is advised to avoid the complication of barium peritonitis. Evaluation with abdominal pelvic CT scan may assist in identification of a fistula and associated abscess. Recognition of an intraperitoneal gastrointestinal leak or fistula formation usually requires immediate surgery, unless the fistula drained spontaneously through the abdominal wall or vaginal cuff.
An enterocutaneous fistula arising from the small bowel and draining spontaneously through the abdominal incision may be managed successfully with medical therapy. Therapy should include nasogastric decompression, replacement of intravenous fluids as well as TPN, and appropriate antibiotics to treat an associated mixed bacterial infection. If the infection is under control and there are no other signs of peritonitis, the surgeon may consider allowing potential resolution of the fistula over a period of up to 2 weeks. Some authors suggested the use of somatostatin to decrease intestinal tract secretion and allow earlier healing of the fistula. In some cases, the fistula will close spontaneously with this mode of management. If the enterocutaneous fistula does not close with conservative medical management, surgical correction with resection, bypass, or reanastomosis will be necessary.
A rectovaginal fistula that occurs following gynecologic surgery is usually the result of surgical trauma that may have been aggravated by the presence of extensive adhesions and scarring in the rectovaginal septum associated with endometriosis, pelvic inflammatory disease, or pelvic malignancy. A small rectovaginal fistula may be managed with a conservative medical approach, in the hope that decreasing the fecal stream will allow closure of the fistula. A small fistula that allows continence except for an occasional leak of flatus may be managed conservatively until the inflammatory process in the pelvis resolves. At that point, usually several months later, correction of the fistula is appropriate. Large rectovaginal fistulas for which there is no hope of spontaneous closure are best managed by performing an initial diverting colostomy followed by repair of the fistula after inflammation resolves. After the fistula closure is healed and deemed successful, the colostomy can be reversed.
Thromboembolism
Risk Factors
Deep venous thrombosis and pulmonary embolism are largely preventable, yet significant complications in postoperative patients. The magnitude of this problem is relevant to the gynecologist, because 40% of all deaths following gynecologic surgery are directly attributed to pulmonary emboli, and it is the most frequent cause of postoperative death in patients with uterine or cervical carcinoma (125,126).
The causal factors of venous thrombosis were first proposed by Virchow in 1858 and include a hypercoagulable state, venous stasis, and vessel endothelial injury. Risk factors include major surgery; advanced age; nonwhite race; malignancy; history of deep venous thrombosis, lower extremity edema, or venous stasis changes; presence of varicose veins; being overweight; a history of radiation therapy; and hypercoagulable states, such as factor V Lieden, pregnancy, and use of oral contraceptives, estrogens, or tamoxifen. Intraoperative factors associated with postoperative deep venous thrombosis include increased anesthesia time, increased blood loss, and the need for transfusion in the operating room. It is important to recognize these risk factors and to provide the appropriate level of venous thrombosis prophylaxis (127,128). The levels of thromboembolism risk are listed in Table 22.11.
Table 22.11 Thromboembolism Risk Stratification
|
Low Risk |
|
Minor surgery |
|
No other risk factorsa |
|
Moderate Risk |
|
Age >40 years and major surgery |
|
Age <40 years with other risk factorsa and major surgery |
|
High Risk |
|
Age >60 years and major surgery |
|
Cancer |
|
History of deep venous thrombosis or pulmonary embolism |
|
Thrombophilias |
|
Highest Risk |
|
Age >60 and cancer or history of venous thromboembolism |
|
aRisk factors: obesity, varicose veins, history of deep venous thrombosis or pulmonary embolism, current estrogen, tamoxifen, or oral contraceptive use. |
Prophylactic Methods
A number of prophylactic methods significantly reduced the incidence of deep venous thrombosis, and a few studies included a large enough patient population to show a reduction in fatal pulmonary emboli (129). The ideal prophylactic method would be effective, free of significant side effects, well accepted by the patient and nursing staff, widely applicable to most patients, and inexpensive.
Low-Dose Heparin
The use of small doses of subcutaneously administered heparin for the prevention of deep venous thrombosis and pulmonary embolism is the most widely studied of all prophylactic methods. More than 25 controlled trials demonstrated that heparin given subcutaneously 2 hours preoperatively and every 8 to 12 hours postoperatively is effective in reducing the incidence of deep venous thrombosis. The value of low-dose heparin in preventing fatal pulmonary emboli was established by a randomized, controlled multicenter international trial, which demonstrated a significant reduction in fatal postoperative pulmonary emboli in general surgery patients receiving low-dose heparin every 8 hours postoperatively (129). Trials of low-dose heparin in gynecologic surgery patients showed a significant reduction in postoperative deep venous thrombosis.
Although low-dose heparin is considered to have no measurable effect on coagulation, most large series noted an increase in the bleeding complication rate, especially a higher incidence of wound hematoma (130). Although relatively rare, thrombocytopenia is associated with low-dose heparin use and was found in 6% of patients after gynecologic surgery (130). If patients remain on low-dose heparin for more than 4 days, it is reasonable to check their platelet count to assess the possibility of heparin-induced thrombocytopenia.
Low-Molecular-Weight Heparin
Low-molecular-weight heparins (LMWH) are fragments of heparin that vary in size from 4,500 to 6,500 Da. When compared with unfractionated heparin, LMWH have more anti-Xa and less antithrombin activity, leading to less effect on partial thromboplastin time and possibly leading to fewer bleeding complications (131). An increased half-life of 4 hours results in increased bioavailability when compared with unfractionated heparin. The increase in half-life of LMWH allows the convenience of once-a-day dosing.
Randomized controlled trials compared LMWH with unfractionated heparin in patients undergoing gynecologic surgery. In all studies, there was a similar incidence of deep venous thrombosis (DVT). Bleeding complications were similar between the unfractionated heparin and LMWH groups (132). A meta-analysis of general surgery and gynecological surgery patients from 32 trials indicated that daily LMWH administration is as effective as unfractionated heparin in DVT prophylaxis without any difference in hemorrhagic complications (133).
Mechanical Methods
Stasis in the veins of the legs occurs while the patient is undergoing surgery and continues postoperatively for varying lengths of time. Stasis occurring in the capacitance veins of the calf during surgery, plus the hypercoagulable state induced by surgery, are the prime factors contributing to the development of acute postoperative DVT. Prospective studies of the natural history of postoperative DVT showed that the calf veins are the predominant site of thrombi and that most thrombi develop within 24 hours of surgery (134).
Although probably of only modest benefit, reduction of stasis by short preoperative hospital stays and early postoperative ambulation should be encouraged for all patients. Elevation of the foot of the bed, raising the calf above heart level, allows gravity to drain the calf veins and should further reduce stasis.
Graduated Compression Stockings
Controlled studies of graduated compression stockings are limited but do suggest modest benefit when they are carefully fitted (135). Poorly fitted stockings may be hazardous to some patients who develop a tourniquet effect at the knee or midthigh (126). Variations in human anatomy do not allow perfect fit of all patients to available stocking sizes. The simplicity of graduated compression stockings and the absence of significant side effects are probably the two most important reasons that they are included in routine postoperative care. Compared to thigh length stockings, calf-high stockings appear to offer the same degree of venous thromboembolism protection.
Intermittent Pneumatic Compression
The largest body of literature dealing with the reduction of postoperative venous stasis deals with intermittent compression of the leg by pneumatically inflated sleeves placed around the calf or leg during intraoperative and postoperative periods. Various pneumatic compression devices and leg sleeve designs are available, and the literature has not demonstrated superiority of one system over another. Calf compression during and after gynecologic surgery significantly reduces the incidence of DVT on a level similar to that of low-dose heparin. In addition to increasing venous flow and pulsatile emptying of the calf veins, intermittent pneumatic compression appears to augment endogenous fibrinolysis, which may result in lysis of very early thrombi before they become clinically significant (136).
The duration of postoperative external pneumatic compression differed in various trials. External pneumatic compression may be effective when used in the operating room and for the first 24 hours postoperatively in patients with benign conditions who will ambulate on the first postoperative day (136,137).
External pneumatic compression used in patients undergoing major surgery for gynecologic malignancy reduced the incidence of postoperative venous thromboembolic complications by nearly threefold, but only if calf compression was applied intraoperatively and for the first 5 postoperative days (138,139). Patients with gynecologic malignancies may remain at risk for a longer period than general surgical patients because of stasis and hypercoagulable states; therefore, these patients appear to benefit from longer use of intermittent pneumatic compression.
Intermittent pneumatic leg compression has no significant side effects or risks and is considered slightly more cost-effective when compared with pharmacologic methods of prophylaxis (140). Compliance in wearing the leg compression while in bed is of utmost importance, and the patient and nursing staff should be educated to the proper regimen for maximum benefit.
The use of low-dose heparin or LMWH or intermittent pneumatic compression is a reasonable strategy in the care of women at moderate risk for postoperative venous thromboembolism. In high-risk patients, consideration should be given to using a pharmacologic method along with intermittent pneumatic compression.
Management of Postoperative Deep Venous Thrombosis and Pulmonary Embolism
Because pulmonary embolism is the leading cause of death following gynecologic surgical procedures, identification of high-risk patients and the use of prophylactic venous thromboembolism regimens are essential parts of management (125,126,141).
The early recognition of DVT and pulmonary embolism and immediate treatment are critical. Most pulmonary emboli arise from the deep venous system of the leg following gynecologic surgery; the pelvic veins are a known source of fatal pulmonary emboli.
The signs and symptoms of DVT of the lower extremities include pain, edema, erythema, and prominent vascular pattern of the superficial veins. These signs and symptoms are relatively nonspecific; 50% to 80% of patients with these symptoms will not have DVT (142). Conversely, approximately 80% of patients with symptomatic pulmonary emboli have no signs or symptoms of thrombosis in the lower extremities (143). Because of the lack of specificity when signs and symptoms are recognized, additional tests should be performed to establish the diagnosis of DVT.
Diagnosis
Doppler Ultrasound B-mode duplex
Doppler imaging is the most common technique for the diagnosis of symptomatic venous thrombosis, especially when it arises in the proximal lower extremity. With duplex Doppler imaging, the femoral vein can be visualized and clots may be seen directly (144). Compression of the vein with the ultrasound probe tip allows assessment of venous collapsibility; the presence of a thrombus diminishes vein wall collapsibility. Doppler imaging is less accurate when evaluating the calf and the pelvic veins.
Venography
Although venography is the standard technique for diagnosis of DVT, other diagnostic studies are accurate when performed by a skilled technologist and, in nearly all patients, may replace the need for contrast venography. Venography is moderately uncomfortable, requires the injection of a contrast material that may cause allergic reaction or renal injury, and may result in phlebitis in approximately 5% of patients (145). If the results of noninvasive imaging are normal or inconclusive and the clinician remains concerned given clinical symptoms, venography should be performed to obtain a definitive answer.
Magnetic Resonance Venography
In addition to having a sensitivity and specificity comparable to venography, magnetic resonance venography (MRV) may detect thrombi in pelvic veins that are not imaged by venography (146). The primary drawback to MRV is the time involved in examining the lower extremity and pelvis and the expense of this technology.
Treatment
Deep Venous Thrombosis
The treatment of postoperative DVT requires the immediate institution of anticoagulant therapy. Treatment may be with either unfractionated heparin or LMWH, followed by 6 months of oral anticoagulant therapy with warfarin (Coumadin).
Unfractionated Heparin
After venous thromboembolism is diagnosed, unfractionated heparin should be initiated to prevent proximal propagation of the thrombus and allow physiological thrombolytic pathways to dissolve the clot. An initial bolus of 80 U per kilogram is given intravenously, followed by a continuous infusion of 1,000 to 2,000 U per hour (18 U/kg/hour). Heparin dosage is adjusted to maintain activated partial thromboplastin time (APTT) levels at a therapeutic level 1.5 to 2.5 times the control value. Initial APTT should be measured after 6 hours of heparin administration and the dose adjusted as necessary. Patients having subtherapeutic APTT levels in the first 24 hours have a 15-fold increased risk of recurrent VTE when compared to patients who are adequately anticoagulated. Patients should be managed aggressively using intravenous heparin to achieve prompt anticoagulation. A weight-based nomogram is helpful in achieving a therapeutic APTT level (Table 22.12) (147). Oral anticoagulant (warfarin) administration may be started on the first day of heparin infusion. The international normalized ration (INR) should be monitored daily until a therapeutic level is achieved (2.0 to 3.0 times normal value). The change in the INR resulting from warfarin administration often precedes the anticoagulant effect by approximately 2 days, during which time low protein C levels are associated with a transient hypercoagulable state. Therefore, heparin should be administered until the INR was maintained in a therapeutic range for at least 2 days, confirming proper warfarin dose. Intravenous heparin may be discontinued in 5 days if an adequate IRN level is established.
Table 22.12 Heparin Administration for Treatment of Deep Venous Thrombosis or Pulmonary Embolism: Weight-Based Nomogram
|
Time of Administration |
Dose |
|
Initial dose |
80-U/kg bolus, then 18 U/kg/h |
|
The APTT should be measured every 6 h and the heparin dose adjusted as follows: |
|
|
APTT <35 seconds (<1.2 × control) |
80-U/kg bolus, then 4 U/kg/h |
|
APTT 35–45 seconds (1.2–1.5 × control) |
40-U/kg bolus, then 2 U/kg/h |
|
APTT 46–70 seconds (1.5–2.3 × control) |
No change |
|
APTT 71–90 seconds (2.3–3 × control) |
Decrease infusion rate by 2 U/kg/h |
|
APTT >90 seconds (>3 × control) |
Hold infusion for 1 h, then decrease infusion rate by 3 U/kg/h |
|
APTT, activated partial thromboplastin time. |
|
|
Reprinted from Raschke RA, Reilly BM, Guidry JR, et al. The weight-based heparin dosing nomogram compared with a “standard care” nomogram. Ann Intern Med 1993;119:874–881, with permission. |
|
Low-Molecular-Weight Heparin
Two LMWH preparations (enoxaparin and dalteparin) were effective in the treatment of venous thromboembolism and have a cost-effective advantage over intravenous heparin in that they may be administered in the outpatient setting. The dosages used in treatment of thromboembolism are unique and weight adjusted according to each LMWH preparation. Because LMWH has a minimal effect on APPT, serial laboratory monitoring of these levels is not necessary. Similarly, monitoring of anti-Xa activity (except in difficult cases or those with renal impairment) is not of significant benefit in a dose adjustment of LMWH. The increased bioavailability associated with LMWH allows for twice-a-day dosing, potentially making outpatient management an option for a subset of patients. A meta-analysis involving more than 4,000 patients from 22 trials suggests that LMWH is more effective, safer, and less costly when compared with unfractionated heparin in preventing recurrent thromboembolism(148).
Pulmonary Embolism
Many of the signs and symptoms of pulmonary embolism are associated with other, more commonly occurring pulmonary complications following surgery. The classic findings of pleuritic chest pain, hemoptysis, shortness of breath, tachycardia, and tachypnea should alert the physician to the possibility of a pulmonary embolism. Many times the signs are subtle and may be demonstrated only by a persistent tachycardia or a slight elevation in the respiratory rate. Patients suspected of pulmonary embolism should be evaluated initially by chest x-ray, electrocardiography, and arterial blood gas assessment. Any evidence of abnormality should be further evaluated by a spiral CT scan of the chest or a ventilation-perfusion lung scan. A high percentage of lung scans may be interpreted as “indeterminate.” In this setting, careful clinical evaluation and judgment are required to decide whether pulmonary arteriography should be performed to document or exclude the presence of a pulmonary embolism.
The treatment of pulmonary embolism is as follows:
1. Immediate anticoagulant therapy, identical to that outlined for the treatment of DVT, should be initiated.
2. Respiratory support, including oxygen and bronchodilators and an intensive care setting, if necessary.
3. Although massive pulmonary emboli are usually quickly fatal, rarely pulmonary embolectomy is successful.
4. Pulmonary artery catheterization with the administration of thrombolytic agents bears further evaluation and may be important in patients with massive pulmonary embolism.
5. Vena cava interruption may be necessary in situations in which anticoagulant therapy is ineffective in the prevention of rethrombosis and repeated embolization from the lower extremities or pelvis. A vena cava filter may be inserted percutaneously above the level of the thrombosis and caudad to the renal veins. In most cases, anticoagulant therapy is sufficient to prevent repeat thrombosis and embolism and to allow the patient’s own endogenous thrombolytic mechanisms to lyse the pulmonary embolus.
Management of Medical Problems
Endocrine Disease
The three most frequent endocrine disorders that occur in patients undergoing gynecologic surgery are diabetes mellitus, thyroid disease, and adrenal abnormalities. The pathophysiology of these disorders aids in understanding the effects of surgery on patients with these problems.
Diabetes Mellitus
According to the American Diabetes Association, 9.3 million American women, or 10.2% of all women older than 20 years, suffer from diabetes (149). Approximately 50% of individuals with diabetes mellitus (DM) will require surgery during their lives (150). Many of these procedures are a direct result of the complications of DM: retinopathy, nephropathy, large- and small-vessel occlusive disease, and coronary artery disease. It is the direct effect of DM on the end organs that determines the risk of surgery, rather than the type or duration of surgery, or the management of the condition itself. Diabetes mellitus is a complicated medical disorder of glucose metabolism that is related to a lack of production of, or resistance to, insulin.
Patients with DM experience exaggerated hyperglycemia during surgery. This hyperglycemia is multifactorial in origin and is secondary to increased catecholamine production, which inhibits pancreatic release of insulin and causes increased insulin resistance at the end organs. Elevations in instrumental hormones, such as cortisol, growth hormone, and glucagon, enhance gluconeogenesis and glycogenolysis (151). Goals of the preoperative assessment and perioperative management are to ensure metabolic homeostasis and to anticipate problems arising from preexisting complications.
Preoperative Risk Assessment
Preoperative risk assessment for diabetes should begin with a review of systems. Nocturia, polyuria, polydipsia, glucosuria, obesity, previous gestational diabetes, ethnicity, and family history are relevant aspects of the history. The current criteria for diagnosis of diabetes include (152):
1. Polyuria, polydipsia, or unexplained weight loss with a random nonfasting glucose of ≥200 mg/dL, or
2. Fasting glucose ≥126 mg/dL (in which fasting is defined as no food intake for 8 hours), or
3. Two-hour oral glucose tolerance test of 75 g, with serum glucose ≥200 mg/dL, or
4. Hemoglobin A1c ≥6.5%.
Confirmation of the diagnosis requires repeating the same test on a different day or concordant results of two different tests simultaneously.
Preoperative risk assessment in the previously diagnosed individual with diabetes should begin with the knowledge of the type of diabetes. Type 1 (insulin dependent) diabetes, or type 2 diabetes (noninsulin dependent), should be established because the perioperative management of each differs. The patient’s routine glucose management strategies, glucose levels, medications, and baseline hemoglobin A1c should be assessed (153). The presence of end-organ complications of diabetes should be documented.
Large- and small-vessel arterial occlusive disease is the single most important risk factor in the preoperative setting. A careful history and physical examination should be performed to determine the presence or absence of coronary artery or cerebral vascular disease (150). When extended surgery is possible, as with surgery for gynecologic cancer, exercise stress testing or dipyridamole-thallium imaging should be considered to rule out occult coronary artery disease. Perioperative beta-blockade should be continued for patients already on beta-blockers at baseline. For patients with inducible ischemia, coronary artery disease, or multiple clinical risk factors for heart disease, perioperative beta-blockade should be considered, with initiation and careful titration of medication several weeks prior to surgery (154,155). Assessment of end-organ disease in the retina, kidney, and carotid arteries or evidence of peripheral vascular disease by the presence of foot ulcers should alert the clinician to the presence of small- or large-vessel disease. Diabetic nephropathy should be documented carefully preoperatively. Imaging studies using contrast dye should be avoided, and alternative testing should be performed to reduce the incidence of acute tubular necrosis. If a contrast study must be performed, adequate hydration both before and after the procedure is essential, and oral metformin should be withheld for 24 to 48 hours after the procedure.
Diabetes is associated with increased perioperative infections (156). Preoperative evaluation should include examination of the skin and urine sediment to detect asymptomatic infection. Wound infections, skin infections, pneumonia, and urinary tract infections account for two-thirds of the postoperative complications in patients with diabetes (151). There is a known predisposition for patients with DM to have increased colonization by methicillin-resistant Staphylococcus aureus, increased infections by gram-negative and staphylococcal bacteria, and an increased incidence of gram-negative and group B streptococcal sepsis (157–159). Seven percent of individuals with diabetes will have postoperative gram-negative sepsis, a rate approximately seven times higher than that of the nondiabetic population. These complications occur more often in patients with poor glucose control, probably caused by impaired leukocyte function in the presence of hyperglycemia (160,161). Individuals with DM have an increased risk of wound dehiscence and wound infection, possibly related to an impaired immune function, with changes in phagocytosis, cell-mediated immunity, and intracellular bactericidal activity (162). Autonomic neuropathy was documented in patients with DM, and these autonomic impairments can lead to intraoperative hypotension, cardiac arrhythmias, sudden death and abnormal motility of the esophagus, stomach, and small intestine (151). Peripheral sensory and motor neuropathies may or may not be present. The presence of any manifestations of autonomic neuropathy intraoperatively should prompt close monitoring of the affected organ system in the postoperative period.
The traditional goal for glucose control perioperatively is to maintain the glucose level below 200 mg/dL (151,153). Significant debate continues regarding whether strict glycemic control below 110 mg/dL may be beneficial in critically ill patients (163,164). Perioperative hyperglycemia (>250 mg/dL) is associated with increased susceptibility to infection and poor wound healing. Extreme hyperglycemia predisposes type 1 DM patients to metabolic acidosis, and surgery should be canceled until normal acid-base balance is documented. Hyperosmolar hyperglycemic nonketotic states must be recognized before surgery. Electrolyte disturbances, especially those related to sodium and potassium, should be corrected preoperatively. Hypoglycemia should be avoided during the perioperative period.
The history and type of DM are important factors to consider when devising a perioperative management plan. Patients with noninsulin-dependent diabetes (type 2) whose condition is controlled with oral hypoglycemic agents or diet are best treated with intravenous fluids containing no dextrose and should not be given insulin intraoperatively. Oral administration of hypoglycemic agents should be discontinued when the patient ceases oral intake of food, and hyperglycemic episodes in the perioperative period are treated with sliding-scale regular insulin if blood sugar levels exceed 200 mg/dL (151,153).
Insulin-dependent or type 1 diabetes poses a more difficult problem. These patients are insulin deficient and therefore require a basal rate of insulin at all times. Likewise, they require a baseline intake of glucose. They risk developing diabetic ketoacidosis whether or not they are eating (153). Preoperatively, the goals include avoiding ketoacidosis and hypoglycemia, and, to a lesser extent, hyperglycemia. Traditionally, approximately one-third to one-half of the patient’s usual daily dose of NPH insulin (intermediate acting) is given subcutaneously the morning of surgery. Omit any short-acting insulin without oral intake. An infusion of 5% dextrose should be given while being restricted from oral intake. Additional regular insulin can be administered in the operating room as needed (150,153). If patients are normally on a continuous insulin infusion, they may continue at their usual infusion rate. There is no single regimen that is superior for the intraoperative management of type 1 diabetic patients. A continuous intravenous insulin infusion is indicated for patients with unstable type 1 diabetes, those who require emergency surgery while in ketoacidosis, and those undergoing long, complex procedures (161). Consultation with endocrine and anesthesia colleagues can be helpful in managing these complex regimens.
Postoperative Management
Postoperative monitoring of patients with DM includes careful monitoring of serum glucose levels. If an intravenous insulin regimen is used, blood glucose levels must be checked every 1 to 2 hours. If a sliding-scale insulinadministration is used, blood glucose should be checked and documented approximately every 6 hours until the patient is eating and stable on her preoperative regimen. The serum glucose level should be maintained at less than 250 mg/dL, and ideally below 140 mg/dL when fasting and below 180 mg/dL with random draws (165,166). For type 2 diabetics, oral hypoglycemics can be restarted when the patient resumes eating, except with metformin, which requires normal renal and liver function (153).
It is essential to prevent the development of severe hypoglycemia or hyperglycemia and the associated complications of diabetic ketoacidosis or a hyperosmolar state. Rigorous perioperative management may obviate some of the infectious and wound-healing complications that are more common in these patients (167).
Thyroid Syndromes
Thyroid dysfunction should be suspected in any patient with a history of hyperthyroidism, use of thyroid replacement medication or antithyroid medication, prior thyroid surgery, or radioactive iodine therapy.
Hyperthyroidism
Diffuse toxic goiter (Grave’s disease) is the most common cause of hyperthyroidism and results from abnormal stimulation of the thyroid gland by antithyroid antibodies. Other causes of hyperthyroidism include multinodular goiter, excess thyroid hormone, or thyroiditis. Any signs or symptoms suggestive of weight loss, tachycardia, atrial fibrillation, goiter, or proptosis should initiate a more extensive laboratory evaluation of thyroid function. Total thyroxin, free triiodothyronine (T3), free thyroxin (T4), and thyroid-stimulating hormone (TSH) tests are useful in diagnosis. In hyperthyroidism, the free T4level will be elevated, and the TSH level will be suppressed (154). A new diagnosis of hyperthyroidism necessitates postponement of elective surgery until adequate treatment with antithyroid medication is received because of the risk of thyroid storm. Thyroid storm is associated with mortality of up to 40% (168). Stable thyroid conditions do not require any special preoperative treatments or tests. Ideally, an euthyroid state should be maintained for 3 months before elective surgery. In emergent situations, beta-blockers can be used to counter sympathomimetic drive such as palpitations, diaphoresis, and anxiety. Antithyroid medications such as propylthiouracil (PTU) or radioactive iodine do not render patients euthyroid quickly enough for urgent surgery. Radioactive iodine requires 6 to 18 weeks to establish a euthyroid state (154). When thyroid dysfunction is corrected and maintained for several months, elective surgery can proceed without additional perioperative monitoring. Antithyroid medications should be resumed with return of bowel function. If a prolonged delay in resumption of oral intake is encountered, PTU and methimazole can be administered rectally (169). When time does not permit establishment of a euthyroid state preoperatively, oral administration of PTU and a beta-blocker can be implemented for 2 weeks before surgery, and with careful monitoring, optimal results can be achieved(170). Alternatively, oral beta-blockers, glucocorticoids, and sodium iopanoate can be used for 5 days, followed by surgery on day 6 (169). In the emergent setting, close monitoring of the patient for tachycardia, arrhythmias, and hypertension is necessary. Beta-blockers can control these symptoms until definitive therapy can be initiated after recovery from surgery.
Any signs suggestive of the development of thyroid storm—including hemodynamic instability, tachycardia, arrhythmias, hyperreflexia, diarrhea, fever, delirium, or congestive heart failure—mandate transfer to an intensive care setting for optimal monitoring and management in consultation with a medical endocrinologist. Such thyroid instability can be triggered by underlying infection, which requires diagnosis and treatment to facilitate management of this medical emergency. The mortality rate from thyroid storm is reportedly between 10% and 75% (169). Treatment of thyroid storm consists of beta-blockers, thioamides, iodine, iodinated contrast agents, and corticosteroids (151). Aspirin should not be given for fever in the patient with thyroid storm because it may interfere with the protein binding of T4 and T3, resulting in increased free serum concentrations (151).
Hypothyroidism
The incidence of hypothyroidism is approximately 1% in the adult population, and 5% in adults older than 50 years (154). In women older than 60 years, the incidence of hypothyroidism may approach 6% (168). Hypothyroidism is 10 times more common in women than in men (154). Many such cases are secondary to previous antithyroid therapy (radioactive iodine or thyroidectomy) for hyperthyroidism. The most common primary cause of hypothyroidism is Hashimoto’s thyroiditis, an autoimmune condition (154). A history of lethargy, cold intolerance, lassitude, weight gain, fluid retention, constipation, dry skin, hoarseness, periorbital edema, and brittle hair can be indicative of inadequate thyroid function. In this setting, physical findings of increased relaxation phase of deep tendon reflexes, cardiomegaly, pleural or pericardial effusions, or peripheral edema should stimulate further investigation of thyroid function by assessment of TSH and free T4 levels. Hypothyroidism decreases cardiac output by 30% to 50% as a result of decreased stroke volume and heart rate (171). Hyponatremia may be associated with hypothyroidism because of the inability of the kidneys to excrete water (171). When elective surgery is planned for severely hypothyroid patients, surgery should be postponed until thyroid replacement therapy is initiated (154). In patients with mild or moderate hypothyroidism, the delay of surgery is controversial (154).
For young patients with mild to moderate hypothyroidism, a starting dose of 1.6 μg/kg of thyroid hormone replacement can be given. In elderly patients, thyroxin dosage (0.025 mg once a day) should be given with interval dose increases every 4 to 6 weeks until the patient is euthyroid (168). Dosage levels can ultimately be titrated against TSH levels. In severely hypothyroid patients requiring urgent or emergent surgery, intravenous T3 or T4 may be given, along with intravenous corticosteroids to avoid consequences of unrecognized adrenal insufficiency (151,154).
In the immediate postoperative setting, T4 therapy can be held for 5 to 7 days while waiting for return of bowel function because the half-life of circulating T4 is approximately 5 to 9 days (170). If more than 5 to 7 days of decreased bowel function are expected, T4 can be given by the intramuscular or intravenous route at approximately 80% of the oral dose (171,172).
Adrenal Insufficiency
Adrenal insufficiency may result in catastrophic postoperative complications, including death. The most common cause of adrenal insufficiency in the surgical patient is secondary to the exogenous use of corticosteroids. The physician should ascertain whether a patient used exogenous steroids for asthma (including inhaled steroids), malignant conditions, arthritis, or irritable bowel syndrome. The type of steroid use, the route, the dose, the duration, and the temporal relationship to the timing of the surgical procedure must be determined. The type of surgical procedure and its associated stress should be taken into consideration. The use of high doses of exogenous steroids for prolonged periods can cause circulatory collapse, and they have adverse effects on wound healing and immunocompetence.
The daily replacement dose of cortisol is approximately 5 to 7.5 mg of prednisone. Suppression of the hypothalamic–pituitary–adrenal (HPA) axis by exogenous steroids for more than a few weeks may produce relative adrenal insufficiency. When systemic steroids are used for longer periods, adrenal insufficiency may persist for up to 1 year. Short courses of low-dose oral steroids (<5 mg of prednisone in a single morning dose for any duration of time, alternate-day dosing of short-acting glucocorticoids, and any dose of corticosteroids given for less than 3 weeks) are not thought to cause clinically significant suppression of the HPA axis (151,172). Use of inhaled corticosteroids of over 0.8 mg per day or class I topical glucocorticoids of 2 g per day or more may cause suppression (172).
If either the dose or duration of glucocorticoid administration exceeds the preceding regimen, biochemical tests are recommended to preoperatively evaluate the function of the adrenal gland. The easiest and safest test to assess HPA function is the cosyntropin stimulation test. Cosyntropin, a synthetic analogue of adrenocorticotropic hormone, is given in a dose of 250 μg intravenously, and a blood sample is collected 30 minutes after the injection and assayed for plasma cortisol. A plasma cortisol value of greater than 18 to 20 μg/dL indicates adequate adrenal function (151,154). If the history regarding exogenous steroid use is unclear, the cosyntropin stimulation test should be considered as a preoperative test to determine whether the patient will need perioperative glucocorticoid coverage. The amount of glucocorticoid replacement should be equivalent to the normal physiologic response to surgical stress (Table 22.13) (173).
Table 22.13 Guidelines for Adrenal Supplementation Therapya
|
Medical or Surgical Stress |
Corticosteroid Dosage |
|
Minor |
|
|
Inguinal hernia repair |
25 mg of hydrocortisone or 5 mg of methylprednisolone IV on day of procedure only |
|
Colonoscopy |
|
|
Mild febrile illness |
|
|
Mild-moderate nausea/vomiting |
|
|
Gastroenteritis |
|
|
Moderate |
|
|
Open cholecystectomy |
50–75 mg of hydrocortisone or 10–15 mg of methylprednisolone IV on day of procedure |
|
Hemicolectomy |
|
|
Significant febrile illness |
|
|
Pneumonia |
|
|
Severe gastroenteritis |
|
|
Severe |
|
|
Major cardiothoracic surgery |
100–150 mg of hydrocortisone or 20–30 mg |
|
Whipple procedure |
|
|
Liver resection |
|
|
Pancreatitis |
|
|
Critically Ill |
|
|
Sepsis-induced hypotension or shock |
50–100 mg of hydrocortisone IV every 6–8 h or 0.18 mg/kg/h as a continuous infusion + 50 μg/d of fludrocortisone until shock resolved. |
|
May take several days to a week or more, then gradually taper, following vital signs and serum sodium. |
|
|
IV, intravenously. |
|
|
aPatients receiving 5 mg/d or less of prednisone should receive their normal daily replacement but do not require supplementation. Patients who receive greater than 5 mg/d of prednisone should receive the above therapy in addition to their maintenance therapy. |
|
|
Reprinted from Coursin DB, Wood KE. Corticosteroid supplementation for adrenal insufficiency. JAMA 2002;287:236–240, with permission. |
|
For minor surgical stress, such as colonoscopy, the glucocorticoid target is approximately 25 mg of hydrocortisone equivalent on the day of the procedure (173). For moderate surgical stress, for example, open cholecystectomy, the glucocorticoid target is 50 to 75 mg of hydrocortisone equivalent on the day of the procedure and tapered quickly for 1 to 2 days (173). The patient should receive her normal daily dose preoperatively, followed by 50 mg of hydrocortisone intravenously administered intraoperatively. For major surgical stress, such as liver resection, the glucocorticoid target range is 100 to 150 mg hydrocortisone equivalent on the day of the procedure, tapering rapidly over the next 1 to 2 days to the usual dosage (173). The patient should receive her normal daily dose preoperatively.
Administration of high-dose steroids should be stopped as soon as possible postoperatively because they can inhibit wound healing and promote infection. Hypertension and glucose intolerance can develop. When a prolonged or involved procedure is performed and longer steroid use is necessary, careful tapering may be required. The previously recommended approach was to halve the dose of hydrocortisone on a daily basis until a dose of 25 mg is reached. Eliminating one daily dose each day until the drug is stopped was considered the safest method of withdrawal; no consensus on the timing or duration of steroid tapering exists. Addison’s disease is uncommon but should be considered in the differential diagnosis if the patient develops perioperative hypotension after steroids are withdrawn. In addition to blood and isotonic fluid replacement, a “stress” dose of steroids should be given if adrenal insufficiency is suspected and sepsis and hypovolemia are excluded.
Cardiovascular Diseases
The incidence of perioperative cardiovascular complications decreased markedly as a result of improvements in preoperative detection of high-risk patients, preoperative preparation, and surgical and anesthetic techniques (174).
Preoperative Evaluation
The goal of a preoperative cardiac evaluation is to determine the presence of heart disease, its severity, and the potential risk to the patient during the perioperative period. Every patient should be questioned about symptoms of cardiac disease including chest pain, dyspnea on exertion, peripheral edema, wheezing, syncope, claudication, or palpitations. Patients with a history of cardiac disease should be evaluated for worsening of symptoms, which indicates progressive or poorly controlled disease. Records of previous treatment should be obtained. Prescriptions for antihypertensive, anticoagulant, antiarrhythmic, antilipid, or antianginal medications may be the only indication of cardiac problems. In patients without known heart disease, the presence of DM, hyperlipidemia, hypertension, tobacco use, or a family history of heart disease identifies patients at higher risk for heart disease who should be more carefully screened.
On physical examination, the presence of findings such as hypertension, jugular venous distention, laterally displaced point of maximum impulse, irregular pulse, third heart sound, pulmonary rales, heart murmurs, peripheral edema, or vascular bruits should prompt a more complete evaluation. Laboratory evaluation of patients with known or suspected heart disease should include a blood count and serum chemistry analysis. Patients with heart disease tolerate anemia poorly. Serum sodium and potassium levels are particularly important in patients taking diuretics and digitalis. Blood urea nitrogen and creatinine values provide information on renal function and hydration status. Assessment of blood glucose levels may detect undiagnosed DM. Chest radiography and electrocardiography are mandatory as part of the preoperative evaluation, and the results may be particularly helpful when compared with those of previous studies.
Coronary Artery Disease
Coronary artery disease is a major risk factor for patients undergoing abdominal surgery. In an adult population without a prior history of myocardial infarction, the incidence of myocardial infarction following surgery is 0.1% to 0.7% (175). In patients who had a prior myocardial infarction, the reinfarction rate is 2.8% to 7% (176). The risk of reinfarction is inversely proportional to the length of time between infarction and surgery. At 3 months or less, the risk of reinfarction is 5.7%, and from 3 to 6 months, the rate falls to 2.3%. Six months after myocardial infarction, the reinfarction rate is 1.5% (175). Careful perioperative management can lower the reinfarction rate in patients who had recent infarctions. Perioperative myocardial infarction is associated with a mortality rate of 26% to 70% (177).
Because of the high mortality and morbidity associated with perioperative myocardial infarction, considerable effort is made to predict perioperative cardiac risk. A prospective evaluation of preoperative cardiac risk factors using a multivariate analysis identified independent cardiac risk factors for patients undergoing noncardiac surgery (177). Using these factors, a cardiac risk index was created that placed a patient in one of four risk classes. This cardiac risk index was further modified and validated prospectively, resulting in a tool for clinical risk assessment in nonemergent major noncardiac surgery, the Revised Cardiac Risk Index (178). Risk factors include high-risk surgical procedures, history of ischemic heart disease, history of congestive heart failure, history of transient ischemic attack or stroke, preoperative insulin therapy, and preoperative serum creatinine levels greater than 2.0 mg/dL. Depending on the number of risk factors, the risk of major cardiac events (myocardial infarction, cardiac arrest, pulmonary edema, and complete heart block) range from 0.5% to 9.1% (Table 22.14).
Table 22.14 Major Cardiac Event Rates by the Revised Cardiac Risk Index
Risk assessment is stratified into three major categories: (i) clinical predictors, (ii) functional capacity, and (iii) surgery-specific risk (179). Clinical predictors of increased perioperative cardiac risk were formerly divided into major, intermediate, and minor factors. The intermediate category was replaced by clinical risk factors from the revised cardiac risk index (Table 22.15). The patient’s functional status is assessed by a thorough history (Table 22.16), and self-reported exercise tolerance can be used to predict perioperative risk, based on a system of metabolic equivalents (METS) (180). Surgery-specific risk is subdivided into high-risk procedures (emergent major operations, aortic and vascular procedures, and prolonged surgical procedures associated with large fluid shifts or blood loss), intermediate-risk procedures (intraperitoneal and intrathoracic), and low-risk procedures (endoscopic, breast surgery, and ambulatory procedures). Patients with poor functional capacity and any clinical risk factor undergoing more than low-risk nonemergent surgery should undergo preoperative testing, based on American Heart Association (AHA) guidelines (179).
Table 22.15 Clinical Predictors of Increased Perioperative Cardiovascular Risk
|
Major |
|
Unstable coronary syndromes: acute (≤ 7 days) or recent (7 < days ≤ 1 month) MI, unstable or severe angina |
|
Decompensated congestive heart failure |
|
Significant arrhythmias (high-grade AV block, symptomatic ventricular arrhythmias, supraventricular arrhythmias with uncontrolled ventricular rate) |
|
Severe valvular disease |
|
Intermediate |
|
History of cerebrovascular disease |
|
Prior ischemic cardiac disease |
|
Compensated or prior congestive heart failure |
|
Diabetes mellitus |
|
Renal insufficiency |
|
Minor |
|
Advanced age |
|
Abnormal ECG (LVH, LBBB, ST-T abnormalities) |
|
Rhythm other than sinus |
|
Uncontrolled systemic hypertension |
|
MI, myocardial infarction; AV, atrioventricular; ECG, electrocardiogram; LVH, left ventricular hypertrophy; LBBB, left bundle branch block. |
|
Adapted from Fleisher LA, Beckman JA, Brown KA, et al. 2009 ACCF/AHA focused update on perioperative beta blockade incorporated into the ACC/AHA 2007 guidelines on perioperative cardiovascular evaluation and care for noncardiac surgery: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines. Circulation 2009;120:e169–e276. |
Table 22.16 Functional Capacity Assessment from Clinical History
|
Excellent |
|
Carry 24 lb up eight steps |
|
Carry objects that weigh 80 lb |
|
Outdoor work (shovel snow, spade soil) |
|
Recreation (ski, basketball, squash, handball, jog or walk 5 mph) |
|
Moderate |
|
Have sexual intercourse without stopping |
|
Walk at 4 mph on ground level |
|
Outdoor work (garden, rake, weed) |
|
Recreation (roller-skate, dance) |
|
Poor |
|
Shower and dress without stopping |
|
Basic housework |
|
Walk 2.5 mph on level ground |
|
Recreation (golf, bowl) |
|
Adapted from Mehta RH, Bossone E, Eagle KA. Perioperative cardiac risk assessment for noncardiac surgery. Cardiologia 1999;44:409–418. |
In an effort to quantify preoperative cardiac risk, several tests are used to assess cardiovascular function. Electrocardiogram should be considered for anyone other than asymptomatic persons undergoing low risk procedures. Echocardiography may be used to evaluate left ventricular function (179). Patients who have dyspnea of unknown origin, current or past heart failure, prior cardiomyopathy, or with any of the above factors and no cardiac assessment in the past 12 months should consider echocardiogram testing preoperatively (179). Exercise stress testing before surgery can identify patients who have ischemic heart disease not apparent at rest. AHA guidelines recommend noninvasive stress testing for patients with one to two clinical risk factors, undergoing intermediate risk surgery with poor functional capacity of METS less than 4. Likewise, it is recommended for patients with greater clinical risk factors or those undergoing high-risk surgery (179). These patients are at increased risk of developing cardiac complications in the perioperative period. In a study of patients undergoing peripheral vascular surgery, a high-risk group of patients was identified who had ischemic electrocardiographic changes when they exercised to less than 75% of their maximal predicted heart rate. In this group, the incidence of perioperative myocardial infarction was 25% and the overall cardiac mortality rate was 18.5%. Conversely, no perioperative infarctions occurred in patients who were able to exercise to more than 75% of their maximal predicted heart rate and who had no electrocardiographic evidence of ischemia (181). The prognostic value of stress testing was not supported in another prospective study that found that only an abnormal preoperative resting electrocardiography result was an independent risk factor (182). The exercise stress test must be selectively applied to a high-risk population because its predictive value depends on the prevalence of the disease. It is not prudent to screen all patients preoperatively; it is preferable to rely on a careful history to identify patients with symptoms of cardiac disease for whom the test would be most predictive.
Exercise stress testing is limited in some patients who cannot exercise because of musculoskeletal disease, pulmonary disease, or severe cardiac disease. Dipyridamole-thallium scanning may be used to overcome the limitations of exercise stress testing. This study has a high degree of sensitivity and specificity but a low positive predictive value (179,183). It relies on the ability of dipyridamole to dilate normal coronary arteries but not stenotic vessels. Normally perfused myocardium readily takes up thallium when it is given intravenously. Conversely, hypoperfused myocardium does not show good uptake of thallium when scanned 5 minutes after injection. Reperfusion and uptake of thallium 3 hours after injection identify viable but high-risk myocardium. Old infarctions are identified as areas without uptake. Several studies show an increasing risk of perioperative myocardial infarction dependent on the extent of reperfusion of thallium, or reversible defect, ranging from 3% to 49% (184,185). The dipyridamole-thallium scan is applicable to clinically high-risk patients who are unable to exercise because it uses a medically induced “stress.”
Dobutamine stress echocardiography is another test to evaluate cardiac risk in patients who are unable to exercise. This method identifies regional cardiac wall motion abnormalities after dobutamine infusion to identify patients at high risk for cardiac events. Positive and negative predictive values are similar to those of dipyridamole-thallium testing for a perioperative event (186,187). Dipyridamole-thalliumtesting is preferred for patients with known cardiac arrhythmias, and dobutamine is preferred for patients with bronchospastic lung disease and in those with severe cardiac stenosis (188). Coronary angiography should be considered only in patients who have an indication for angiography independent of the planned surgery, such as patients with acute coronary syndromes, unstable angina, angina refractory to medical therapy, or high-risk results on noninvasive testing.
Preoperative testing should be used discriminately in intermediate-risk patients. Controversy exists regarding the accuracy of these tests to provide prognostic information beyond what is obtained from clinical risk stratification for nonvascular procedures. Diagnostic testing should not lead to unnecessary additional testing or harmful delays in surgery. The American College of Cardiology and the American Heart Association present an updated detailed algorithm that incorporates risk-factor stratification to guide clinicians to proceed directly to surgery, to delay surgery and obtain preoperative noninvasive testing, or to attempt risk factor modification (179).
It is rare for patients who are younger than 50 years and who do not have diabetes, hypertension, hypercholesterolemia, or coronary artery disease to suffer a perioperative myocardial infarction. In contrast, patients with coronary artery disease are at increased risk of myocardial infarction in the postoperative period. Prevention, early recognition, and treatment are important because myocardial infarctions that occur in the postoperative period have mortality rates of up to 25% and are associated with increased rates of cardiovascular death in the 6 months following surgery (189).
Nearly two-thirds of postoperative myocardial infarctions occur during the first 3 days postoperatively (189). Although the pathophysiologic factors are complex, the causes of postoperative myocardial ischemia and infarction are related to decreased myocardial oxygen supply coupled with increased myocardial oxygen requirements. In postoperative patients, conditions that decrease oxygen supply to the myocardium include tachycardia, increased preload, hypotension, anemia, and hypoxia (190). Conditions that increase myocardial oxygen consumption are tachycardia, increased preload, increased afterload, and increased contractility. Tachycardia and increased preload are the most important causes of ischemia, because both conditions decrease oxygen supply to the myocardium while simultaneously increasing myocardial oxygen demand. Tachycardia decreases the diastolic time, which, when the coronary arteries are perfused, decreases the volume of oxygen available to the myocardium. Increased preload increases the pressure exerted by the myocardial wall on the arterioles within it, thus decreasing myocardial blood flow.
Other factors associated with perioperative myocardial ischemia include physiologic responses to the stress of intubation, intravenous or arterial line placement, emergence from anesthesia, pain, and anxiety. These stresses result in catecholamine stimulation of the cardiovascular system, resulting in increased heart rate, blood pressure, and contractility, which may induce or worsen myocardial ischemia. Loss of intravascular volume because of third spacing of fluids or postoperative hemorrhage can induce ischemia.
Postoperative myocardial infarction is often difficult to diagnose. Chest pain, which is present in 90% of nonsurgical patients with myocardial infarction, may be present in only 50% of patients with postoperative infarction because myocardial pain may be masked by coexisting surgical pain and the use of analgesics (175). It is important to maintain a high level of suspicion for postoperative infarction in patients with coronary artery disease. The presence of arrhythmia, congestive heart failure, hypotension, dyspnea, or elevations of pulmonary artery pressure may indicate infarction and should prompt a thorough cardiac investigation and electrocardiographic monitoring. Measurement of creatinine phosphokinase myocardial band (CPK-MB) isoenzyme and troponin T levels are the most sensitive and specific indicators of myocardial infarction, and assessments should be obtained for all patients suspected of myocardial infarction (189).
Despite the high incidence of silent myocardial infarction, routine use of postoperative electrocardiography (ECG) for all patients with cardiovascular disease is controversial. Many patients will exhibit P-wave changes that spontaneously resolve and do not represent ischemia or infarction. Conversely, patients with proven myocardial infarctions may show few, if any, ECG abnormalities. The American College of Cardiology and American Heart Association advise consideration of postoperative surveillance via ST-segment monitoring for myocardial infarction in patients with known or suspected coronary artery disease (191). In a review of over 2,400 patients, the sensitivity of predicting postoperative cardiac events was 55% to 100%, specificity 37% to 85%, positive predictive value 7% to 57%, and negative predictive value 89% to 100% (192). If routine screening of asymptomatic patients is desired, ECG should be performed 24 hours following surgery because significant ECG changes that occur immediately postoperatively will persist for 24 hours. It is prudent to continue serial ECG assessments for at least 3 days postoperatively.
Postoperative management of patients with coronary artery disease is based on maximizing delivery of oxygen to the myocardium and decreasing myocardial oxygen utilization. Most patients benefit from supplemental oxygen in the postoperative period, although special care should be exercised in patients with COPD. Oxygenation can easily be monitored by pulse oximetry. Anemia is detrimental because of loss of oxygen-carrying capacity and resultant tachycardia and should, therefore, be carefully corrected in high-risk patients. Although transfusion criteria are not absolute, all patients with a hemoglobin less than 6 mg/dL, and hemoglobin of 6 to 10 mg/dL with significant cardiac risk factors should be offered blood transfusion (193).
Patients with coronary artery disease may benefit from pharmacologic control of hyperadrenergic states that result from increased postoperative catecholamine production. Beta-blockers decrease heart rate, myocardial contractility, and systemic blood pressure, all of which are increased by adrenergic stimulation. Perioperative use of ß1 selective beta-blocker is shown to significantly reduce perioperative ischemia, myocardial infarction, and overall mortality caused by cardiac death and congestive heart failure in the perioperative period (194–196). The POISE (Perioperative Ischemic Evaluation) trial, a randomized controlled trial of metoprolol, enrolling 8,000 patients undergoing noncardiac surgery, revealed a reduction in cardiovascular death, myocardial infarction, and cardiac arrest. There was an increased risk of stroke and total mortality (197). The AHA provides the following guidelines: Continue beta-blocker therapy in patients on baseline beta-blockers for treatment of cardiac disease. Consider initiating and titrating beta-blockers in patients with coronary artery disease or high cardiac risk (as defined by the presence of more than one clinical risk factor) who are undergoing intermediate-risk surgery (155). Therapy should be initiated at least 1 week before surgery to allow for proper titration. The timing and optimal duration of beta-blocker therapy remains an area of uncertainty. Nevertheless, for patients already on beta-blocker therapy, they should continue it perioperatively because abrupt withdrawal results in a rebound hyperadrenergic state.
Prophylactic use of other agents such as nitroglycerin and calcium-channel blockers remains controversial, as data did not show a consistent benefit toward reducing risk of ischemic cardiac events. Nitroglycerin may cause hypotension, which may worsen cardiac status (155).
Congestive Heart Failure
Patients with congestive heart failure (CHF) face a substantially increased risk of myocardial infarction during and after surgery (177). The postoperative development of pulmonary edema may be associated with a high mortality rate, especially if it occurs in the setting of cardiac ischemia (198,199). Because patients with heart failure at the time of surgery are significantly more likely to develop complications, every effort should be made to diagnose and treat CHF before surgery (178,200). The signs and symptoms of CHF are listed in Table 22.17 and should be assessed based on preoperative history and physical examination. Patients who are able to perform usual daily activities without developing CHF are at limited risk of perioperative heart failure.
Table 22.17 Signs and Symptoms of Congestive Heart Failure
|
1. Presence of an S3 gallop 2. Jugular venous distention 3. Lateral shift of the point of maximal impulse 4. Lower-extremity edema 5. Basilar rales 6. Increased voltage on electrocardiogram 7. Evidence of pulmonary edema or cardiac enlargement on chest radiograph 8. Tachycardia |
To prevent severe postoperative complications, CHF must be corrected preoperatively. Treatment usually relies on aggressive diuretic therapy, although care must be taken to avoid dehydration, which may result in hypotension during the induction of anesthesia. Hypokalemia can result from diuretic therapy and is especially deleterious to patients who are taking digitalis. In addition to diuretics and digitalis, treatment often includes the use of preload- and afterload-reducing agents. Optimal use of these drugs and correction of CHF may be aided by consultation with a cardiologist. It is preferable to continue the usual regimen of cardioactive drugs throughout the perioperative period.
Postoperative CHF frequently results from excessive administration of intravenous fluids and blood products. Other common postoperative causes are myocardial infarction, systemic infection, pulmonary embolism, and cardiac arrhythmias. The cause of postoperative heart failure must be diagnosed because, to be successful, treatment should be directed simultaneously to the underlying cause. Postoperative diagnosis of CHF is more difficult than preoperative diagnosis because the signs and symptoms of CHF are not specific and may result from other causes. The most reliable method of detecting CHF is chest radiography, in which the presence of cardiomegaly or evidence of pulmonary edema is a helpful diagnostic feature.
Acute postoperative CHF frequently manifests as pulmonary edema. Treatment of pulmonary edema may include the use of intravenous furosemide, supplemental oxygen, morphine sulfate, and elevation of the head of the bed. Intravenous aminophylline may be useful if cardiogenic asthma is present. Electrocardiography, in addition to laboratory evaluation, including arterial blood gas, serum electrolyte, and renal function chemistry measurements, should be obtained expediently. If the patient’s condition does not improve rapidly, she should be transferred to an intensive care unit.
Arrhythmias
Nearly all arrhythmias found in otherwise healthy patients are asymptomatic and of limited consequence. In patients with underlying cardiac disease, however, even brief episodes of arrhythmias may result in significant cardiac morbidity and mortality.
Preoperative evaluation of arrhythmias by a cardiologist and anesthesiologist is important because many anesthetic agents and surgical stress contribute to the development or worsening of arrhythmias. In patients undergoing continuous electrocardiographic monitoring during surgery, a 60% incidence of arrhythmias, excluding sinus tachycardia, are reported (201). Patients with heart disease have an increased risk of arrhythmias, most commonly ventricular arrhythmias (201). Patients without cardiac disease are more likely to develop supraventricular arrhythmias during surgery. Patients taking antiarrhythmic medications before surgery should continue taking those drugs during the perioperative period. Initiation of antiarrhythmic medications is rarely indicated preoperatively, but consultation with a cardiologist is recommended for patients in whom arrhythmias are detected before surgery.
Patients with first-degree atrioventricular (AV) block or asymptomatic Mobitz I (Wenckebach) second-degree AV block require no preoperative therapy. A pacemaker is appropriate in patients with symptomatic Mobitz II second- or third-degree AV block before elective surgery (202). In emergency situations, a pacing pulmonary artery catheter can be used. Before performing surgery on patients with a permanent pacemaker, the type and location of the pacemaker should be determined because electrocautery units may interfere with demand-type pacemakers (203). When performing gynecologic surgery on patients with pacemakers, it is preferable to place the electrocautery unit ground plate on the leg to minimize interference by preventing the pacemaker generator from sitting within the electrocautery circuit and to maximize distance from the pacemaker device. If possible, use of bipolar cautery devices are recommended rather than monopolar devices. In patients with a demand pacemaker in place, the pacemaker should be converted preoperatively to the fixed-rate (or asynchronous) mode. Although this can be accomplished oftentimes by placing a magnet over the pacemaker, it may be better to reprogram the pacemaker preoperatively and then again postoperatively. Patients should be monitored continuously intraoperatively with both telemetry and continuous pulse oximeter. Close coordination with anesthesia and cardiology is imperative. Patients with an implantable cardioverter defibrillator device should have their device programmed off prior to surgery and reprogrammed postoperatively (155).
Surgery is not contraindicated in patients with bundle branch blocks or hemiblocks (204). Perioperative mortality rates are not increased by bundle-branch block. Complete heart block rarely develops during noncardiac surgical procedures in patients with conduction system disease. The presence of a left bundle-branch block may indicate the presence of aortic stenosis, which can increase surgical mortality if it is severe.
Valvular Heart Disease
Although there are many forms of valvular heart disease, two types—aortic and mitral stenosis—primarily are associated with significantly increased operative risk (205). Patients with significant aortic stenosis appear to be at greatest risk, which is increased in the presence of atrial fibrillation, congestive heart failure, or coronary artery disease. Significant stenosis of aortic or mitral valves should be repaired before elective gynecologic surgery (176).
Severe valvular heart disease usually is evident during physical exertion. Common findings in such patients are listed in Table 22.18. The classic history presented by patients with severe aortic stenosis includes exercise dyspnea, angina, and syncope, whereas symptoms of mitral stenosis are paroxysmal and effort dyspnea, hemoptysis, and orthopnea. Most patients have a remote history of rheumatic fever. Severe stenosis of either valve is considered to be a valvular area of less than 1 cm2, and diagnosis can be confirmed by echocardiography or cardiac catheterization.
Table 22.18 Signs and Symptoms of Valvular Heart Disease
|
Aortic stenosis 1. Systolic murmur at right sternal border, which radiates into carotids 2. Decreased systolic blood pressure 3. Apical heave 4. Chest radiograph with calcified aortic ring, left ventricular enlargement 5. Electrocardiogram with high R waves, depressed T waves in lead I, and precordial leads |
|
Mitral stenosis 1. Precordial heave 2. Diastolic murmur at apex 3. Mitral opening snap 4. Suffused face and lips 5. Chest radiograph with left atrial dilation 6. Electrocardiogram with large P waves and right axis deviation |
Patients with valvular abnormalities are subdivided by the American Heart Association into risk groups for the development of subacute bacterial endocarditis following surgery. Patients in the highest risk groups should receive prophylactic antibiotics immediately preoperatively to prevent subacute bacterial endocarditis (Table 22.8). As defined by the American Heart Association, only patients with prosthetic cardiac valves, congenital heart disease, and cardiac transplantation who develop cardiac valvulopathy should receive perioperative endocarditis prophylaxis (76). All other patients do not require antibiotics for subacute bacterial endocarditis prophylaxis. Routine prophylaxis for GI or GU procedures is not recommended. Only in cases of a known infection of the GI or GU tract should antibiotics coverage for enterococcus with amoxicillin or ampicillin or vancomycin be provided.
Patients with aortic and mitral stenosis tolerate sinus tachycardia and other tachyarrhythmias poorly. In patients with aortic stenosis, sufficient levels of digitalis should be provided to correct preoperative tachyarrhythmias, and propranolol may be used to control sinus tachycardia. Patients with mitral valve stenosis often have atrial fibrillation and, if present, digitalis should be used to reduce rapid ventricular response.
Patients with mechanical heart valves usually tolerate surgery well (206). These patients should receive antibiotic prophylaxis (Table 22.8). If the patient is taking aspirin therapy, it should be discontinued 1 week before the procedure and restarted as soon as it is considered safe by the surgeon. Patients with a bileaflet aortic valve with no risk factors (atrial fibrillation, previous thromboembolism, left ventricular dysfunction, a hypercoagulable state, older generation thrombogenic valve) generally do not require anticoagulation bridging. Warfarin should be stopped 72 hours prior to the procedure and resumed 24 hours after the procedure. In contrast, patients with a mechanical aortic valve and any above mentioned risk factor, or a mechanical mitral valve, should be bridged with intravenous unfractionated heparin when the INR falls below 2. The heparin drip should be stopped approximately 6 to 8 hours before the procedure and restarted as soon as possible after surgery when the patient is deemed stable from postoperative bleeding risk. The heparin bridge can be stopped when the INR reaches therapeutic levels (207).
In the postoperative period, patients with mitral stenosis should be carefully monitored for pulmonary edema because they may not be able to compensate for the amount of intravenous fluid administered during surgery. Prevention of tachycardia is important, as it may lead to pulmonary edema. Patients with mitral stenosis frequently have pulmonary hypertension and decreased airway compliance. They may require more pulmonary support and therapy postoperatively, including prolonged mechanical ventilation.
For patients with significant aortic stenosis, it is imperative that a sinus rhythm be maintained during the postoperative period. Even sinus tachycardia can be deleterious because it shortens the diastolic time. Bradycardia less than 45 beats per minute should be treated with atropine. Supraventricular dysrhythmias may be controlled with verapamil or direct-current cardioversion. Particular attention should be provided to the maintenance of proper fluid status, digoxin levels, electrolyte levels, and blood replacement.
Hypertension
Patients with controlled essential hypertension have no increased risk of perioperative cardiac morbidity or mortality (208). Patients with concomitant heart disease are at elevated risk and should be completely evaluated by a cardiologist preoperatively. Laboratory studies should include an ECG, chest radiography, blood count, urinalysis, and serum electrolytes and creatinine measurement. Antihypertensive medications should be continued perioperatively. Beta-blockers should be continued, parenterally if necessary, to avoid rebound tachycardia, hypercontractility, and hypertension. Clonidinemay cause significant rebound hypertension if withdrawn acutely. Angiotensin converting enzyme inhibitor agents and angiotensin II receptor antagonists are associated with increased intraoperative hypotension and perioperative renal dysfunction possibly resulting from a hypovolumic state. It may be prudent to withhold these agents on the morning of surgery and resume them postoperatively when good renal function and euvolumia is confirmed (155).
Patients with diastolic pressures higher than 110 mm Hg or systolic pressures higher than 180 mm Hg should receive medication to control their hypertension before surgery. Beta-blockers may be particularly effective agents for treatment of preoperative hypertension (179). Chronically hypertensive patients are very susceptible to intraoperative hypotension because of impaired autoregulation of blood flow to the brain and require a higher mean arterial pressure to maintain adequate perfusion (209). During induction of anesthesia, episodes of hypertension occur, and such episodes are seen more frequently in patients with baseline hypertension.
Postoperative hypertension is usually treated parenterally because gastrointestinal absorption may be diminished, and transdermal absorption can be erratic in patients who are cold and rewarming. Commonly used parenteral antihypertensives are listed in Table 22.19.
Table 22.19 Common Parenteral Antihypertensives
Perioperative Antiplatelet Agents
Increasing numbers of patients undergo coronary revascularization procedures, otherwise known as coronary artery bypass grafting, or percutaneous coronary intervention, typically stent placement. With the evolution of bare metal and drug-eluting stents, perioperative management of cardiovascular thrombotic risk versus perioperative bleeding and mortality is challenged. Given that drug-eluting stents generally require 12 months' treatment with dual agent aspirin and thienopyridine (i.e., clopidogrel), the American College of Cardiology and American Heart Association (ACC/AHA) guidelines recommend avoiding elective surgery within 12 months of drug-eluting stent placement. When surgery cannot wait, the ACC/AHA recommends continuation of aspirin perioperatively, discontinuation of thienopyridine 5 days prior to surgery, and resuming it as soon as possible postoperatively. Ultimately the risk of perioperative morbidity secondary to bleeding must be weighed against the risk of repeat thrombosis and cardiovascular morbidity and mortality. If a patient requires new placement of a cardiac stent and requires a noncardiac surgery in the following 12 months, placement of a bare metal stent is recommended rather than a drug-eluting stent, as these require only 4 to 6 weeks of dual-antiplatelet therapy. Again, aspirin should be continued perioperatively. Following a newly placed bare metal stent, noncardiac surgery should be scheduled at least 30 to 45 days after the stent placement to decrease cardiac morbidity (179).
Hemodynamic Monitoring
Hemodynamic monitoring is integral to the perioperative management of patients with cardiovascular and pulmonary diseases. The major impetus for this advancement resides in the need for the quantitative estimate of cardiac function, resulting in the development of bedside pulmonary artery catheterization. The impact of monitoring cardiac function is demonstrated by the significant reduction of myocardial infarctions in high-risk patients who are aggressively monitored for 72 to 96 hours postoperatively (175).
Before the development of the pulmonary artery catheter, central venous pressure (CVP) measurement was used to assess intravascular volume status and cardiac function. To measure the CVP, a catheter is placed in the central venous system, most frequently the superior vena cava. A water manometer or a calibrated pressure transducer is connected to the CVP line, allowing an estimation of right atrial pressure. Right atrial pressure is determined by the balance between cardiac output and venous return. Cardiac output is determined by heart rate, myocardial contractility, preload, and afterload. If the pulmonary vascularity and left ventricular function are normal, the CVP accurately reflects the left ventricular end-diastolic pressure (LVEDP). The LVEDP reflects cardiac output or systemic perfusion and was considered the standard estimator of left ventricular pump function. Venous return is determined primarily by the mean systemic pressure, which propels blood toward the heart, balanced against resistance to venous return, which acts in the opposite direction. If right ventricular function is normal, the CVP accurately reflects intravascular volume.
Left and right ventricular function is frequently abnormal or discordant; therefore, the relationship of CVP to cardiac function and to intravascular volume is not maintained. When this occurs, measurement of pulmonary artery occlusion pressure can be used to accurately assess volume status and cardiovascular function. The use of a pulmonary artery catheter allows detection of changes in cardiovascular function with more sensitivity and rapidity than clinical observation.
The balloon-tipped pulmonary artery catheter (Swan-Ganz catheter) can measure pulmonary artery and pulmonary artery occlusion pressures (210). The catheter can measure cardiac output, be used to perform intracavitary electrocardiography, and provide temporary cardiac pacing. The standard pulmonary artery occlusion catheter is a 7-French, radiopaque, flexible, polyvinyl chloride, 4-lumen catheter with a 1.5-mL latex balloon at its distal tip. Most often, a right internal jugular cannulation is used for placement of the catheter, because this site provides the most direct access into the right atrium and has fewer complications when compared with a subclavian route of placement. After the catheter is placed into the right atrium, the balloon is inflated, and the catheter is pulled by blood flow through the right ventricle into the pulmonary artery. The position of the catheter can be identified and followed by the various pressure waveforms generated by the right atrium, right ventricle, and pulmonary artery. As the catheter passes through increasingly smaller branches of the pulmonary artery, the inflated balloon eventually occludes the pulmonary artery.
The distal lumen of the catheter, which is beyond the balloon, measures left atrial pressure (LAP) and, in the absence of mitral valvular disease, LAP approximates LVEDP. Pulmonary–capillary wedge pressure (PCWP) equals the LAP, which equals LVEDP and is normal at 8 to 12 mm Hg. Because the standard pulmonary artery catheter has an incorporated thermistor, thermodilution studies can be performed to determine cardiac output. This thermodilution method is performed by injecting cold 5% dextrose in water through the proximal port of the catheter, which cools the blood entering the right atrium. The change in temperature measured at the more distal thermistor (4 cm from the catheter tip) generates a curve proportional to cardiac output. Knowledge of the cardiac output is helpful in establishing cardiovascular diagnoses. For example, a patient with hypotension, low-to-normal wedge pressure, and a cardiac output of 3 L per minute is most likely hypovolemic. The same patient with a cardiac output of 8 L per minute is probably septic with resultant low systemic vascular resistance.
Pulmonary artery catheters are associated with a small but significant complication rate. The complications can be grouped into those occurring during venous cannulation or insertion, during maintenance and use, and those related to interpretation of hemodynamic data (210). The most common problems encountered during venous access are cannulation of the carotid or subclavian artery and introduction of a pneumothorax. Problems resulting from the catheter itself include dysrhythmias, sepsis, and disruption of the pulmonary artery. Pulmonary artery catheters (PAC) should be placed under the supervision of experienced personnel in a setting in which complications can be rapidly diagnosed and treated. Accessory equipment such as resuscitation equipment and an external pacing device must be immediately available. Ultrasound and fluoroscopic equipment if available may aid in PAC placement (211).
The effect of PAC use on patient outcome is controversial. Several large trials did not confer a definite benefit to PAC use. One multi-institutional study examined the association of PAC placement within the first 24 hours of hospital stay and its associated outcomes. They found a higher mortality rate in patients who received a PAC than those who did not have a PAC (212). The study was limited because it was retrospective and not randomized. A randomized controlled trial of 1,994 high-risk (American Society of Anesthesiologists class III or IV risk) patients age 60 or older undergoing urgent or elective major noncardiac surgery compared outcomes of those who underwent PAC placement versus standard care. Results analyzed by a blinded assessor revealed no benefit of PAC over standard care with central venous catheters (213). Another randomized controlled trial enrolling 65 intensive care units in the United Kingdom found no difference in mortality among critically ill patients managed with or without a PAC (214). A meta-analysis of 13 randomized controlled trials of PAC use found no significant difference in mortality rates and an increased use of ionotropes and intravenous vasodilators (215). Routine preoperative use of PAC in noncardiac surgery patients is no longer indicated. Use of PAC in critically ill patients postoperatively remains controversial.
Hematologic Disorders
The presence of hematologic disorders, although uncommon in gynecologic patients, significantly affects operative morbidity and mortality and should be considered routinely in preoperative evaluation. Preoperative assessment should include consideration of anemia, platelet and coagulation disorders, white blood cell function, and immunity.
Anemia
Moderate anemia is not in itself a contraindication to surgery because it can be corrected by transfusion. If possible, surgery should be postponed until the cause of the anemia can be identified and the anemia corrected without resorting to transfusion. By tradition, anesthetic and surgical practice recommended a hemoglobin level of greater than 10 g/dL or a hematocrit of greater than 30%. Data suggest a lower tolerance for pre- and intraoperative transfusion threshold to improve intra- and postoperative morbidity and mortality (216–219). It remains that no universal “transfusion threshold” is agreed upon, but that a hematocrit of less than 24% should prompt strong consideration (219). The circulating blood volume provides oxygen-carrying capacity and tissue oxygenation. Usually this capacity is reflected by the hemoglobin level and hematocrit. Under certain circumstances this is not the case. After an acute blood loss or before plasma expansion by extracellular fluid occurs, hematocrit measurements may be normal despite a low circulating blood volume. Conversely, overhydration may result in low hematocrit and hemoglobin levels despite adequate red blood cell mass.
Individual tolerance of anemia depends on overall physical fitness and cardiovascular reserve. The effects of anemia depend on its magnitude, the rate at which it occurs, the oxygen requirement of the patient, and the ability of physiologic mechanisms to compensate (220). Maintenance of adequate tissue perfusion requires an increase in cardiac output as hemoglobin concentration falls (193). In the healthy patient, oxygen delivery is unchanged when it falls below 7 g/dL (221). In contrast, a patient with ischemic heart disease will not tolerate anemia as well (222). The presence of cardiac, pulmonary, or other serious illness justifies a more conservative approach to the management of anemia. Patients with longstanding anemia may have normal blood volume levels and tolerate surgical procedures well. There is no evidence that mild to moderate anemia increases perioperative morbidity or mortality (222).
Autologous blood transfusion may be an acceptable option for patients. Patients with normal hematocrit levels may store autologous blood preoperatively to reduce the need for allogenic blood transfusion and minimize the risk of infections and immunologic problems (193). Recombinant human erythropoietin may increase collection and reduce preoperative anemia in these patients (223,224). Intraoperative blood collection and homologous transfusion can be employed to limit the need for allogenic blood transfusion.
Autologous blood donation is advocated as a safer alternative for the patient; however, the use of preoperative autologous blood donation has come under scrutiny (225,226). Preoperative autologous blood may lead to more liberal blood transfusion, iatrogenic anemia, volume overload, and bacterial contamination (227). Preoperative autologous blood donation is poorly cost-effective (228). The National Heart, Lung, and Blood Institute does not recommend collection of autologous blood for procedures with a likelihood of transfusion less than 10%, such as uncomplicated abdominal and vaginal hysterectomies (229).
Platelet and Coagulation Disorders
Surgical hemostasis is provided by platelet adhesion to injured vessels, which plugs the opening as the coagulation cascade is activated, resulting in the formation of fibrin clots. Functional platelets and coagulation pathways are necessary to prevent excessive surgical bleeding. Platelet dysfunction is encountered preoperatively more frequently than coagulation disorders.
Platelets may be deficient in both number and function. The normal peripheral blood count is 150,000 to 400,000 per mm3, and the normal lifespan of a platelet is approximately 10 days. Although there is no clear-cut correlation between the degree of thrombocytopenia and the presence or amount of bleeding, several generalizations can be made. If the platelet count is higher than 100,000/mm3 and the platelets are functioning normally, there is little chance of excessive bleeding during surgical procedures. Patients with a platelet count higher than 75,000/mm3 almost always have normal bleeding times, and a platelet count higher than 50,000/mm3 is probably adequate. A platelet count lower than 20,000/mm3 often will be associated with severe and spontaneous bleeding. Platelet counts higher than 1,000,000/mm3 are often, paradoxically, associated with bleeding.
If the patient’s platelet count is lower than 100,000/mm3, an assessment of bleeding time should be obtained. If the bleeding time is abnormal and surgery must be performed, an attempt should be made to raise the platelet count by administering platelet transfusions immediately before surgery. In patients with immune destruction of platelets, human leukocyte antigen (HLA)–matched donor-specific platelets may be required to prevent rapid destruction of transfused platelets. If surgery can be postponed, a hematology consultation should be obtained to identify and treat the cause of the platelet abnormality.
Abnormally low platelet counts result from either decreased production or increased consumption of platelets. Although there are numerous causes of thrombocytopenia, most are exceedingly uncommon. Decreased platelet production may be drug induced and is associated with the use of sulfonamides, cinchona alkaloids, thiazide diuretics, NSAIDs, gold salts, penicillamine, anticonvulsants, and heparins (230). Decreased platelet count is a feature of several diseases, including vitamin B12 and folate deficiency, aplastic anemia, myeloproliferative disorders, renal failure, and viral infections. Inherited congenital thrombocytopenia is extremely rare. More commonly, thrombocytopenia results from immune destruction of platelets by diseases such as idiopathic thrombocytopenia purpura and collagen vascular disorders. Consumptive thrombocytopenia is a feature of disseminated intravascular coagulation, which is encountered most frequently in conjunction with sepsis or malignancy in the preoperative population.
Platelet dysfunction most often is acquired, but may be inherited. Occasionally, a patient with von Willebrand disease, the second most common inherited disorder of coagulation, may be encountered in the preoperative setting. More commonly, platelet dysfunction results from the use of drugs (e.g., aspirin and amitriptyline), and in patients with resulting prolonged bleeding time, the drug should be withheld for 7 to 10 days before surgery. Uremia and hepatic diseases can affect platelet function.
Platelet dysfunction is more difficult to diagnose than abnormalities of platelet count. A history of easy bruising, petechiae, bleeding from mucous membranes, or prolonged bleeding from minor wounds may signify an underlying abnormality of platelet function. Such dysfunction can be identified with the help of a bleeding time, but full characterization of the underlying etiology should be carried out with hematologic consultation. If at all possible, surgery should be postponed until therapy is instituted.
Disorders of the coagulation cascade often are diagnosed through a personal or family history of excessive bleeding during minor surgery, childbirth, or menses. Many women with menorrhagia are referred for surgical intervention and require a thorough preoperative evaluation for possible inherited disorders of hemostasis, such as factor VIII (hemophilia), factor IX (Christmas disease), factor XI deficiencies, and von Willebrand disease. Von Willebrand disease is the most common hereditary bleeding disorder, with prevalence in the general population of roughly 1% (231). Seventy percent to 90% of patients with von Willebrand disease have menorrhagia (231). Identified women can be treated effectively with desmopressin nasal spray, avoiding unanticipated or excessive bleeding during surgery (232). In the absence of a genetic diagnosis, the diagnosis of von Willebrand disease is difficult and involves a combination of clinical and laboratory assessments, including von Willebrand factor antigen and von Willebrand factor functional activity or ristocetin cofactor assay (232). Physiologic fluctuations occur with von Willebrand factor levels, requiring repeat testing and consultation or referral to a hematologist. It is recommended that women presenting with menorrhagia without obvious pelvic abnormalities should be routinely screened for inherited bleeding disorders before undergoing invasive procedures.
There are few commonly prescribed drugs that affect coagulation factors, the exceptions being warfarin and heparin. Disease states that may be associated with decreased coagulation factor levels are primarily liver disease, vitamin K deficiency (secondary to obstructive biliary disease, intestinal malabsorption, or antibiotic reduction of bowel flora), and disseminated intravascular coagulation.
Preoperative laboratory screening for coagulation deficiencies is controversial. Routine screening is not warranted in patients who do not have historical evidence of a bleeding problem (233). Patients who are seriously ill or who will be undergoing extensive surgical procedures should undergo testing preoperatively to determine prothrombin time, partial thromboplastin time, fibrinogen level, and platelet count.
White Blood Cells and Immune Function
Abnormally high or low white blood cell counts are not an absolute contraindication to surgery; they should be considered relative to the need for surgery. Evaluation of an elevated or decreased white blood cell count should be undertaken before elective surgery. Patients with absolute granulocyte counts lower than 1,000/mm3 are at increased risk of severe infection and perioperative morbidity and mortality and should undergo surgery only for life-threatening indications (234).
Blood Component Replacement
Packed red blood cells, which may be stored for several weeks, are used for most postoperative transfusions. Most clotting factors are stable for long periods. The exceptions are factors V and VIII, which decrease to 15% and 50% of normal, respectively. Most hematologic problems observed in the postoperative period are related to perioperative bleeding and blood component replacement. Although the primary cause of the bleeding is usually lack of surgical hemostasis, other factors, including deranged coagulation, may compound the problem. Such coagulopathy can result from massive transfusion (less than one blood volume) and is thought to be caused by dilution of platelets and labile coagulation factors by platelet- and factor-poor packed red blood cells (PRBCs), fibrinolysis, and disseminated intravascular coagulation.
A review in Transfusion questioned the traditional practice of limiting blood component replacement in massive transfusion. Summarizing 14 articles and encompassing nearly 4,600 patients, the conclusions note a decrease in all-cause mortality with more liberal transfusion of platelets and fresh frozen plasma (FFP) (235).
A task force for the American Society of Anesthesiologists recommended critical values for replacement in patients with massive transfusion and microvascular bleeding (193):
1. Platelet transfusion usually is indicated for counts less than 50,000/mm3 (with intermediate platelet counts, i.e., 50,000/mm3 to 100,000/mm3, the transfusion of platelet concentrates should be based on the risk of more significant bleeding).
2. Fresh frozen plasma therapy is indicated if the prothrombin or activated partial thromboplastin time values exceed 1.5 times the normal value.
3. Cryoprecipitate transfusion is indicated if fibrinogen concentrations decrease to less than 80 to 100 mg/dL.
Cryoprecipitate transfusions are recommended for prophylaxis in nonbleeding perioperative patients with fibrinogen deficiencies or von Willebrand disease refractory to desmopressin acetate and bleeding patients with von Willebrand disease (232).
Donor blood is stored in the presence of citrate, which chelates calcium to prevent clotting, increasing the theoretical risk of hypocalcemia following massive transfusion. Citrate is metabolized at a rate equivalent to 20 U of blood transfused per hour; thus, routine supplementation of calcium is unnecessary. Close monitoring of calcium levels is required in patients with hypothermia, liver disease, or hyperventilation because citrate metabolism may be slowed. Hepatic metabolism of citrate to bicarbonate can result in metabolic alkalosis following transfusion, resulting in subsequent hypokalemia, despite the high level of extracellular potassium in stored blood.
Pulmonary Disease
In patients undergoing abdominal surgery, several pulmonary physiologic changes manifest secondary to immobilization, anesthetic irritation of the airways, and the splinting of breathing that inevitably occurs secondary to incisional pain. Pulmonary physiologic changes include a decrease in the functional residual capacity (FRC), an increase in ventilation perfusion mismatching, and impaired mucociliary clearance of secretions from the tracheobronchial tree (236). Risk factors for postoperative pulmonary complications include the following (237,238) (Table 22.20):
Table 22.20 Predictors of Postoperative Pulmonary Complicationsa
|
Parameter |
Value |
|
Maximal breathing capacity |
<50% predicted |
|
FEV1 |
<1 L |
|
FVC |
<70% predicted |
|
FEV1/FVC |
<65% predicted |
|
Pao2 |
<60 mm Hg |
|
Paco2 |
>45 mm Hg |
|
FEV, forced expiration volume; FVC, forced vital capacity; Pao2, partial pressure of oxygen, arterial; Paco2, partial pressure of carbon dioxide, arterial. |
|
|
aComplication defined as atelectasis or pneumonia. |
|
|
Adapted from Blosser SA, Rock P. Asthma and chronic obstructive lung disease. In: Breslow MJ, Miller CJ, Rogers MC, eds. Perioperative management. St. Louis, MO: Mosby, 1990:259–280. |
|
• Upper abdominal or thoracic, or abdominal aortic aneurysm surgery
• Surgical procedure time longer than 3 hours
• COPD
• Smoking within 2 months of surgery
• Use of pancuronium for general anesthesia
• New York Heart Association Class II pulmonary hypertension
• General anesthesia
• Pancuronium
• Emergency surgery
• Poor nutrition (serum albumin <3.5mg/dL or BUN <8).
Probable risk factors include general anesthesia, preoperative partial pressure of carbon dioxide, arterial (PaCO2) greater than 45 mm Hg, and emergency surgery. Risk factors that could increase the postoperative risk are upper respiratory infection, abnormal chest x-ray, and age. Preoperative pulmonary function testing is of unproven value in patients not undergoing thoracic surgery (237). This is based on multiple reasons: first, a lower limit of forced expiration volume (FEV1) did not correlate with pulmonary complications; second, pulmonary complications can occur in the context of a normal FEV1; and third, if an FEV1 were able to predict a pulmonary complication putting the patient at increased risk, it would not change the need for aggressive postoperative prophylactic measures (237). The routine performance of preoperative arterial blood gas measurements does not improve assessment of risk (236). Noninvasive pulse-oximetry measurements can detect patients with hypoxemia (236). The presence of hypercarbia on arterial blood gas measurements does not predict postoperative pulmonary complications (236).
Young, healthy patients rarely have abnormal chest x-rays. Chest x-rays should not be performed routinely in these patients. Most patients with abnormal chest x-rays have history or physical examination findings suggestive of pulmonary disease. Chest x-rays should be limited to patients older than 50 years of age, with a history of smoking or of pulmonary disease, who have evidence of cardiopulmonary disease and in whom a metastatic malignancy is suspected. Although they have limited usefulness in predicting postoperative pulmonary complications, chest x-rays provide a valuable baseline in elderly patients, patients with chronic pulmonary diseases, and those with known lung metastases (236–238).
Asthma
Asthma affects approximately 22 million individuals in the United States, including 6% of children (239). It is characterized by a history of episodic wheezing, physiologic evidence of reversible obstruction of the airways either spontaneously or following bronchodilator therapy, and pathologic evidence of chronic inflammatory changes in the bronchial submucosa. Asthma is not a disease of airway physiology in which hypertrophy and increased contractility of bronchial smooth muscle is the dominant lesion; rather, it is an inflammatory disease affecting the airways that secondarily results in epithelial damage, leukocytic infiltration, and increased sensitivity of the airways to a number of stimuli. The treatment of asthma is directed toward relaxing the airways and alleviating inflammation (239).
Multiple stimuli are noted to precipitate or exacerbate asthma, including environmental allergens or pollutants, respiratory tract infections, exercise, cold air, emotional stress, nonselective beta-adrenergic blockers, and NSAIDs (239). Management of asthma includes removal of the inciting stimuli as well as use of appropriate pharmacologic therapy. The optimal therapy for asthma involves managing the acute symptoms and long-term management of the inflammatory component of the disease.
Pharmacotherapy of Asthma
The treatment of asthma is divided into long-term control modalities and short-term modalities. Recognizing the underlying pathophysiology in asthma as an inflammatory condition, inhaled corticosteroids are the cornerstone for maintenance therapy. Onset of action is slow (several hours), and up to 3 months of steroid therapy may be required for optimal improvement of bronchial hyperresponsiveness. Even with acute bronchospasm, steroid treatment can enhance the beneficial effect of beta-adrenergic treatment. During acute exacerbations of asthma, a short course of oral steroids, in addition to inhaled steroids, may be necessary. For adults with chronic asthma, only a minority will require chronic oral steroid therapy. Patients taking oral steroids should receive intravenous steroid support in the form of 100 mg of hydrocortisone IV every 8 hours perioperatively, sharply tapering within 24 hours of surgery to avoid adrenal insufficiency. Other long-term control therapies include (239):
1. Leukotriene modifiers (i.e., montelukast): These agents interfere with leukotrienes, substances released from mast cells, eosinophils, and basophils important in the inflammatory response.
2. Cromolyn sodium: Highly active in the treatment of seasonal allergic asthma in children and young adults. It is usually not as effective in older patients or in patients in whom asthma is not allergic in nature.
3. Immunomodulators: Omalizumab, a monoclonal antibody to immunoglobulin E (IgE), has gained support for prevention and may be an important adjunct in symptomatic suppression.
4. Long term beta2-adrenergic agonists (i.e., salmeterol): Although not appropriate for single agent management or use in mild disease, they are an important adjunct in the suppression of symptoms in patients with significant disease.
5. Methylxanthines (i.e., theophylline): These were relegated to third-line status in the management of asthma. Theophylline toxicity can develop when other drugs such as ciprofloxacin, erythromycin, allopurinol, Inderal, or cimetidineare concomitantly administered. Therapeutic serum levels must be monitored closely.
β2-adrenergic agonists remain the first-line drugs for acute asthma attacks. These drugs, inhaled four to six times daily, rapidly relax smooth muscle in the airways and are effective for up to 6 hours. Studies of beta2 agonists in chronic asthma failed to show any influence of these agents on the inflammatory component of asthma. β2 agonists are recommended for short-term relief of bronchospasm (“rescue inhalers”) or as first-line treatment for patients with very infrequent symptoms or symptoms provoked solely by exercise (239).
Anticholinergic agents are weak bronchodilators that work via inhibition of muscarinic receptors in the smooth muscle of the airways. The quaternary derivatives such as ipratropium bromide (Atrovent) are available in an inhaled form that is not absorbed systemically. Anticholinergic drugs may provide additional benefit in conjunction with standard steroid and bronchodilator therapy but should not be used as single-agent therapy because they do not inhibit mast cell degranulation, do not have any effect on the late response to allergens, and do not have an anti-inflammatory effect (239).
Perioperative Management of Asthma
In patients with asthma, elective surgery should be postponed whenever possible until pulmonary function and pharmacotherapeutic management are optimized. The most recent guidelines of the American Academy of Allergy, Asthma and Immunology’s recommend three interventions to reduce perioperative pulmonary complications related to asthma (239):
1. Review the patient’s asthmatic control, including the need for oral steroids.
2. Optimize the patient’s symptomatic control through the use of long-acting pharmacotherapy, including oral steroids if needed.
3. For patients on oral steroid therapy within 6 months of therapy or for patients using large doses of inhaled corticosteroids, consider perioperative stress dose steroids.
For mild asthma, the use of inhaled beta-adrenergic agonists preoperatively may be all that is required. For chronic asthma, optimization of steroid therapy will greatly decrease alveolar inflammation and bronchiolar hyperresponsiveness. Inhaled beta2-agonists should be added to therapy as needed for further control of asthma. Each drug prescribed should be used in maximal dosage before adding an additional agent. Preoperative treatment with combined corticosteroids and an inhaled beta2-adrenergic agonist for a 5-day period may decrease the risk of postoperative bronchospasm in patients with asthma (240). For patients undergoing emergent surgery who have significant bronchoconstriction, a multimodal approach should be instituted, including aggressive bronchodilator inhalation therapy and intravenous steroid therapy. The role of spirometry, outside of cardiothoracic procedures, has limited value in predicting postoperative pulmonary complications and should be limited to the confirmation of undiagnosed obstructive pulmonary disease (241).
Chronic Obstructive Pulmonary Disease
COPD is the greatest risk factor for the development of postoperative pulmonary complications. COPD encompasses both chronic bronchitis and emphysema, disease entities that often occur in tandem. Cigarette smoke is implicated in the pathogenesis of both, and any treatment plan must include cessation of smoking (242). Chronic bronchitis is defined as the presence of productive cough on most days for at least 3 months per year and for at least 2 successive years (243). It is characterized by chronic airway inflammation and excessive mucus production. The histologic changes of emphysema include destruction of alveolar septa and distension of airspaces distal to terminal alveoli. The destruction of alveoli results in air trapping, loss of pulmonary elastic recoil, collapse of the airways in expiration, increased work of breathing, and significant ventilation-perfusion mismatching (243). The impaired ability to cough effectively and clear secretions predisposes patients with COPD to atelectasis and pneumonia in the postoperative period.
Patients with COPD and a history of heavy smoking account for most postoperative pulmonary complications in gynecologic surgical patients. The severity of COPD can be determined preoperatively via a thorough history and physical examination. According to recommendations regarding the use of preoperative pulmonary function tests by the American College of Physicians, these should be reserved for individuals in whom COPD is suspected, but unconfirmed (237,241). Typically, patients with COPD demonstrate impaired expiratory air flow, manifested by diminished FEV1, forced vital capacity (FVC).
Data suggest that arterial blood gas measurements may show varying degrees of hypoxemia and hypercapnia: routine use of preoperative arterial blood gas measurement does not stratify patients into a higher risk subset for postoperative complications (236).
The preoperative preparation of the patient at risk for postoperative pulmonary complications should include cessation of smoking for as long as possible preoperatively; whereas 2 to 3 days of smoking abstinence are sufficient for carboxyhemoglobin levels to return to normal. One to 2 weeks of cessation decreases sputum volume. Two months of smoking abstinence is required to significantly lower the risk of postoperative pulmonary complications (236). Longer periods of abstinence can be counseled in patients undergoing elective surgery.
In patients with severe COPD, maximum improvement in airflow limitation can be achieved with a therapeutic trial of high-dose oral corticosteroids followed by a 2-week trial of high-dose inhaled steroid (beclomethasone 1.5 mg per day or the equivalent) in addition to inhaled bronchodilator therapy. Ideally, oral and inhaled steroid therapy should be initiated 1 to 2 weeks preoperatively. Inhaled steroids, in particular, address the inflammatory component of COPD. Oral steroid therapy initiated preoperatively should be maintained throughout the perioperative period and then tapered postoperatively. Beta-adrenergic agonist therapy can be initiated at least 72 hours preoperatively and is beneficial in patients who demonstrate either clinical or spirometric improvement on bronchodilators.
Patients with COPD and an active bacterial infection suggested by purulent sputum should undergo a full course of antibiotic therapy before surgery. The antibiotic used should cover the most likely etiologic organisms, Streptococcus pneumoniae and Haemophilus influenzae. In any patient with acute upper respiratory infection, surgery should be delayed if possible. The use of antibiotics to sterilize the sputum in the absence of evidence of an acute infection should be avoided because this practice may lead to bacterial resistance.
Aggressive pulmonary toilet, including incentive spirometry, chest physical therapy, and continuous positive airway pressure devices, reduced the risk of perioperative pulmonary complications in patients undergoing upper abdominal surgery, many of which can be instituted preoperatively (237).
Postoperative Pulmonary Management
Atelectasis
Atelectasis accounts for more than 90% of all postoperative pulmonary complications. The pathophysiology involves a collapse of the alveoli, resulting in ventilation-perfusion mismatching, intrapulmonary venous shunting, and a subsequent drop in the PaO2. Collapsed alveoli are susceptible to superimposed infection, and if managed improperly, atelectasis will progress to pneumonia. Patients with atelectasis have a decreased FRC as well as decreased lung compliance, resulting in increased work during breathing. Despite the decrease in PaO2, the partial pressure of carbon dioxide (PCO2) remains unaffected unless atelectatic changes progress to large volumes of the lung or preexisting lung disease is present.
Physical findings associated with atelectasis may include a low-grade fever. Auscultation of the chest may reveal decreased breath sounds at the bases or dry rales upon inspiration. Percussion of the posterior thorax may suggest elevation of the diaphragm. Radiologic findings include the presence of horizontal lines or plates on posteroanterior chest x-rays, occasionally with adjacent areas containing hyperinflation. These changes are most pronounced during the first 3 postoperative days.
Therapy for atelectasis should be aimed at expanding the alveoli and increasing the FRC. The most important maneuvers are those that promote maximal inspiratory pressure, which is maintained for as long as possible. This exercise promotes an expansion of the alveoli and secretion of surfactant, which stabilizes alveoli. It can be achieved with aggressive supervised use of incentive spirometry, deep breathing exercises, coughing, and in some cases, the use of positive expiratory pressure with a mask (continuous positive airway pressure). Oversedation should be avoided, and patients should be encouraged to ambulate and change positions frequently. Fiberoptic bronchoscopy for removal of mucopurulent plugs should be reserved for patients who fail to improve with the usual measures.
Cardiogenic (High-Pressure) Pulmonary Edema
Cardiogenic pulmonary edema can result from myocardial ischemia, myocardial infarction, or from intravascular volume overload, particularly in patients who have low cardiac reserve or renal failure. The process usually begins with an increase in the fluid in the alveolar septa and bronchial vascular cuffs, ultimately seeping into the alveoli. Complete filling of the alveoli impairs secretion and production of surfactant. Concomitant with alveolar flooding, there is a decrease in lung compliance, impairment of the oxygen diffusion capacity, and an increase in the arteriolar–alveolar oxygen gradient. Ventilation-perfusion mismatching in the lung results in a decrease in the PaO2, resulting eventually in decreased oxygenation of the tissues and impairment of cardiac contractility.
Symptoms may include tachypnea, dyspnea, wheezing, and use of the accessory muscles of respiration. Clinical signs may include distention of the jugular veins, peripheral edema, rales upon auscultation of the lungs, and an enlarged heart. Radiographic findings may include the presence of bronchiolar cuffing and increased interstitial fluid markings extending to the periphery of the lung. The diagnosis can be confirmed with the use of central hemodynamic monitoring, which will denote an elevated central venous pressure and, more specifically, an elevation in the pulmonary capillary wedge pressure.
The patient’s volume status should be evaluated thoroughly. In addition, myocardial ischemia or infarction should be ruled out by performing ECG and analyzing cardiac enzyme levels. The management of cardiogenic pulmonary edema includes oxygen support, aggressive diuresis, and afterload reduction to increase the cardiac output. In the absence of myocardial infarction, an inotropic agent may be used. Mechanical ventilation should be reserved for cases of acute respiratory failure.
Noncardiogenic Pulmonary Edema (Adult Respiratory Distress Syndrome)
In contrast with cardiogenic pulmonary edema, in which alveolar flooding is a result of an increase in the hydrostatic pressure of the pulmonary capillaries, alveolar flooding in patients with adult respiratory distress syndrome (ARDS) is the result of an increase in pulmonary capillary permeability. The primary pathophysiologic process is one of damage to the capillary side of the alveolar–capillary membrane. This damage results in rapid movement of fluid containing high concentrations of protein from the capillaries to the pulmonary parenchyma and alveoli. Lung compliance decreases and oxygen diffusion capacity is impaired, resulting in hypoxemia. If not managed aggressively, respiratory failure may result; when managed aggressively, the mortality rate associated with ARDS is high. There are a number of causes and several distinct states of ARDS. The causes of ARDS include shock, sepsis, multiple red blood cell transfusions, aspiration injury, inhalation injury, pneumonia, pancreatitis, disseminated intravascular coagulation, and fat emboli (244). Twenty-eight-day mortality is reported between 25% to 40%, with overall mortality as high as 70% (244,245). Irrespective of the cause, which should be identified and treated if possible, the evolving clinical picture and management are very similar.
Clinically, ARDS passes through several stages. Initially, patients develop tachypnea and dyspnea with no remarkable findings on clinical evaluation or on chest x-ray. Chest x-rays eventually reveal bilateral diffuse pulmonary infiltrates. As lung compliance becomes impaired, functional residual capacity, tidal volume, and vital capacity decrease. The PaO2 decreases and, characteristically, increases only marginally with oxygen supplementation. An attempt should be made to maintain the arterial oxygen level above 90%. This may be achievable initially by administering oxygen by mask. For patients with severe hypoxemia, endotracheal intubation with positive-pressure ventilation should be instituted. Traditionally, the goal was to maintain normal arterial gases, with increased minute ventilation and pressure as needed to maintain these, with little insight into the long-term repercussions that this modality employs. Data over the past 5 to 10 years show that “normal” or increased tidal volumes and pressures are linked to significant barotrauma and injury to alveoli. Elevated positive end-expiratory pressure (PEEP) increasingly was used to recruit alveoli, with decreases in the amount of fraction of inspired oxygen (Fio2) and minute ventilation required to maintain oxygenation in this setting, with limited success when compared to lower PEEP levels, controlling for tidal volume and end-inspiratory pressures (246).
Attempts to manage and treat the cause of ARDS must include aggressive efforts toward hemodynamic and circulatory resuscitation in patients with shock. Nosocomial pneumonia is present in 50% of patients with ARDS, and broad-spectrum antibiotic therapy should be administered appropriately for patients with suspected pneumonia or sepsis. Patients who have disseminated intravascular coagulopathy may require replacement with cryoprecipitate or FFP. Other measures for general care should include the placement of a nasogastric tube, gastric acid suppression with H2 blockers, and administration of steroids in patients with the fat emboli syndrome.
Hemodynamic monitoring is invaluable and should be initiated early in the course of the disease process in the appropriate intensive care unit setting. Patients with any evidence of fluid overload should receive aggressive diuresis, whereas others may require fluid resuscitation for maintenance of tissue perfusion while the pulmonary–capillary wedge pressure is maintained below 15 mm Hg. Pulmonary wedge pressure may be falsely elevated when PEEP is being applied. The goal of management is to maintain the lowest pulmonary–capillary wedge pressure, with acceptable cardiac output and blood pressure. In the setting of hypotension and oliguria, inotropic support with dopamine or dobutamine or both is helpful.
With aggressive management, particularly if the inciting cause is identified and treated, ARDS can be reversed during the first 48 hours with few sequelae. After the first 48 hours, progression of the ARDS will cause lung damage that may leave residual pulmonary fibrosis. The long-term outcome is usually apparent within the first 10 days, at which time approximately half of patients are weaned from ventilatory support or they die (244).
Renal Disease
The need for surgical intervention in patients with renal impairment resulted in the development of a very specialized medical approach to their care. Precautions are necessary to compensate for the kidneys' impaired ability to regulate fluids and electrolytes and excrete metabolic waste products. Equally important are the unique problems that develop in patients with chronic renal impairment, including an increased risk of sepsis, coagulation defects, impaired immune function and wound healing, and a propensity to develop specific acid-base abnormalities. Special consideration must be given to a variety of different medications, anesthetic agents, and numerous hematologic and nutritional factors that are important in the successful surgical care of patients with renal insufficiency.
Management of fluid levels and cardiovascular hemodynamics in patients with acute or chronic renal impairment is paramount. Intravascular fluid volume changes that lead to hypertension or hypotension are very common in these patients and often are difficult to manage secondary to autonomic dysfunction, acidosis, and other problems that are inherent to the underlying kidney disease. Patients undergoing dialysis in whom major abdominal or pelvic surgery is contemplated should be treated using invasive monitoring, both intra- and postoperatively. The results of physical examination and CVP monitoring correlate poorly with left cardiac filling pressures. Swan-Ganz catheter measurements will help guide fluid replacement and avoid volume overload. Invasive hemodynamic monitoring should be continued as needed throughout the first postoperative week because third spacing will occur during this period.
Postoperative dialysis usually is necessary to avoid problems associated with fluid overload and hyperkalemia. Dialysis-dependent patients should undergo dialysis approximately 24 hours following surgery. A short-lived but rather significant fall in the number of platelets occurs during dialysis; in addition, heparin is used in hemodialysis equipment to prevent clotting. Because of these factors and concerns about postoperative bleeding, dialysis is usually avoided during the first 12 to 24 hours following surgery. Although ischemic heart disease is the most common cause of death in patients with renal insufficiency, it is not a major cause of perioperative mortality (247). A large percentage of perioperative deaths of patients with renal insufficiency are associated with hyperkalemia that is controlled most effectively by dialysis (248).
Patients with chronic renal failure are at an increased risk for postoperative infections resulting from abnormalities in neutrophil and monocyte function (249). Appropriate preoperative antibiotic prophylaxis and accurate assessment of nutritional status help lower the incidence of postoperative infectious complications.
The major hematologic concern in patients with chronic renal insufficiency is the increased incidence of bleeding. These bleeding problems are secondary to abnormal bleeding times and, in particular, disorders of platelet function related to a decreased amount of factor VIII and von Willebrand antigen in the serum of uremic patients. Anemia, which is common in patients with renal insufficiency, can contribute to prolonged bleeding times (250). Abnormalities in arachidonic acid metabolism, acquired platelet storage pool deficiency, and disturbed regulation of platelet calcium content all contribute to an increased tendency for uremic patients to have significant bleeding during surgery (251). The bleeding time should be routinely checked preoperatively in these patients, and abnormalities should be corrected before surgery. Options for the correction of bleeding time in uremic patients include infusion of desmopressin or cryoprecipitate, both of which act to increase plasma levels of factor VIII and von Willebrand antigen (252,253).
Normal renal function is essential for maintenance of acid-base balance in the body. Patients with renal insufficiency can have a normal anion gap or an elevated anion gap acidosis. When mild renal insufficiency develops, a normal anion gap is present, whereas in more significant and severe renal dysfunction, an elevated anion gap acidosis occurs. Hemodialysis corrects metabolic acidosis. If a patient is severely acidotic (pH <7.15) and emergency surgery is planned, correction of the blood pH to 7.25 using intravenous sodium bicarbonate is indicated. However, correction of metabolic acidosis should be carried out slowly, because in patients with hypocalcemia, seizures may be precipitated (254). It is important to exclude other causes of elevated anion gap acidosis, such as ketoacidosis secondary to diabetes, lactic acidosis secondary to infection, or in rare instances, poisoning with ethylene glycol, methanol, or aspirin.
Impaired kidney function causes phosphate retention by the kidney and impaired vitamin D metabolism. Therefore, hypocalcemia is common in patients with renal insufficiency, but tetany and other signs of hypocalcemia are relatively uncommon because metabolic acidosis increases the level of ionized calcium. Oral phosphate binders, such as aluminum hydroxide (1 to 2 g per meal), and dietary phosphate restriction (1 g per day) is the usual treatment for hypocalcemia–hyperphosphatemia in patients with renal insufficiency. In chronic situations, because of central nervous system toxicity associated with elevated aluminum levels, it is preferable to treat hypocalcemia–hyperphosphatemia with large doses of calcium carbonate (6 to 12 g per day) rather than with the standard aluminum-containing antacids (255).
Approximately 20% of patients with renal insufficiency exhibit clinical evidence of protein calorie malnutrition. Vitamin deficiencies, most notably with water-soluble vitamins, occur with dialysis. Nutritional disturbances in patients with chronic renal insufficiency arise secondary to deficiencies in protein intake, and studies show that, in patients with chronic renal insufficiency, their kidneys are hyperfiltrating (256). Postoperatively, both protein and caloric intake may need to be increased dramatically to meet catabolic demands in surgical patients. As much as 1.5 g/kg of protein and 45 kcal/kg of calories may be needed (256).
Wound healing is impaired in patients with chronic renal failure, and wound dehiscence and evisceration are potential problems. Wound healing is most appropriately aided by nutritional assessment preoperatively and maintenance of adequate caloric and protein intake in the perioperative setting. Antibiotic prophylaxis should be used in these patients, and uremia should be treated with dialysis as indicated. A running mass closure of the midline vertical incision with continuous monofilament sutures should be used to decrease the risk of wound dehiscence and evisceration (256).
Patients with chronic renal disease have an altered ability to excrete drugs and are prone to significant metabolic derangements secondary to the altered bioavailability of many commonly used medications. Because of this, and the effect of dialysis on drug pharmacokinetics, the gynecologic surgeon and nephrologist must be aware of the lowered metabolism and bioavailability of narcotics, barbiturates, muscle relaxants, antibiotics, and other drugs that require renal clearance. Of particular note is the inability of patients with renal insufficiency to clear the neuromuscular blockade caused by pancuronium (257). Care must be taken with D-tubocurarine, especially if repeated doses are given (258). Midazolam, propofol, vecuronium, and atracurium are used safely in patients with renal failure (254). Succinylcholine is reported to cause significant hyperkalemic responses in patients with renal failure (259). When succinylcholine is used in patients with chronic renal insufficiency, careful monitoring of the serum potassium level is necessary (260).
Perioperative acute renal failure in previously normal patients may be caused by decreased renal perfusion, nephrotoxins, or both. Patients with impaired cardiac function, intravascular volume depletion, sepsis, or hypotension fall under the first category. Nephrotoxic medications such as aminoglycosides, chemotherapeutic agents such as cisplatin, or iodinated contrast agents fall under the second category (261–263). The risk of renal impairment becomes cumulative if more than one of these factors exist at the same time, and especially if a variety of factors are associated with intervascular volume depletion (264). Several measurements should be used to avoid acute renal failure. All nephrotoxic drugs should be discontinued when possible. When it is not practical to withdraw medication, strict attention should be paid to the pharmacokinetic characteristics of each drug and to the regular measurements of serum creatinine levels. Patients with diabetes should be given reduced doses of radiocontrast agents and should be well hydrated because they are particularly susceptible to renal injury from these materials (265). Volume repletion is essential to lower the incidence of renal impairment (266).
Liver Disease
Management of perioperative problems in gynecologic patients with liver disease requires a comprehensive understanding of normal liver physiology and the pathophysiology underlying diseases of the liver that may complicate surgery or recovery. Patients with liver disease often have numerous complicated problems involving nutrition, coagulation, wound healing, encephalopathy, and infection.
History and Physical Examination
Patients with a history of alcohol abuse, drug use, hepatitis, jaundice, blood product exposure, or a family member with liver disease should undergo biochemical evaluation. During the physical examination, note should be made of any jaundice, signs of muscle wastage, ascites, right upper quadrant tenderness, palmar erythema, or hepatomegaly.
Laboratory Testing
The biochemical profile (alkaline phosphatase, calcium, lactate dehydrogenase, bilirubin, serum glutamic–oxaloacetic transaminase, cholesterol, uric acid, phosphorous, albumin, total protein, and glucose) is not useful for routine preoperative evaluation (267). Mild abnormalities can result in further extensive testing that requires consultation, delays in surgery, and increased cost without net benefit. A possible exception is selected use of biochemical testing when the history or physical examination reveals abnormalities. Patients with known liver disease should undergo albumin and bilirubin testing using the Child’s risk classification (Table 22.21). This system was originally designed to predict mortality following portosystemic shunt surgery. It divides patients into three classes of severity based on five easily assessed clinical parameters. Measurement of prothrombin time may be helpful in patients with significant histories of liver disease. If a history of hepatitis is ascertained, the patient should be tested for serum aminotransferase, alkaline phosphatase, bilirubin, albumin levels, and prothrombin time. Serologic documentation of hepatitis is important. If a patient has a known malignancy, biochemical testing of the liver may be of some benefit as a screen for metastatic disease, although this was not proven conclusively.
Table 22.21 Child’s Classification of Liver Dysfunction
Anesthesia
With few exceptions, most anesthetic agents, including those administered by epidural or spinal routes, reduce hepatic blood flow and decrease oxygenation of the liver. Other perioperative factors—hemorrhage, intraoperative hypotension, hypercarbia, congestive heart failure, and intermittent positive pressure ventilation, especially in critically ill patients—lead to decreased hepatic perfusion and hypoxia (268).
Drug Metabolism
Patients with altered liver function should be carefully monitored because of the prolonged action of many medications used during surgery. In addition to impaired metabolism, hypoalbuminemia decreases drug binding, which alters serum levels and biliary clearance rates. The degree of hepatic metabolism varies greatly, depending on the type of medication considered. For inhalation anesthetics, isoflurane is preferred because it undergoes minimal hepatic metabolism in comparison with halothane or enflurane. Narcotics, induction agents, sedatives, and neuromuscular blocking agents all undergo abnormal metabolism in patients with decompensated liver disease. Diazepam, meperidine, and phenobarbital cause prolonged depression of consciousness and may precipitate hepatic encephalopathy because of their altered rates of clearance. Sufentanil and fentanyl are the preferred narcotics. Oxazepam, a benzodiazepine that does not undergo hepatic metabolism, is considered safe. Muscle relaxants, such as D-tubocurarine, pancuronium, and vecuronium, cause prolonged neuromuscular blockade in patients with impaired liver function and are not ideal drugs to use in this situation. Atracurium is not metabolized by the liver and is the preferred muscle relaxant for patients with abnormal hepatic function. Succinylcholine metabolism is prolonged in patients with hepatic dysfunction and must be used with great caution (269).
Determination of Operative Risk
Although it is well known that acute hepatobiliary damage results in increased morbidity and mortality in the surgical patient, estimating the operative risk in patients with hepatic dysfunction is difficult based on the history and physical examination. The most accurate method for risk assessment of surgery in patients with hepatic dysfunction is Child’s classification (Table 22.21). Using this system, accurate assessment of morbidity and mortality can be directly related to the degree of liver dysfunction (270). The Child’s classification is useful for patients undergoing a variety of different types of abdominal surgery. Data show operative mortalities of 10%, 30%, and 82% for each of the three Child’s classifications, respectively, while other data called this into question with operative mortality of 2%, 12%, and 12% (271,272). The major cause of perioperative death was often sepsis. This classification correlated significantly with postoperative complications such as bleeding, renal failure, wound dehiscence, and sepsis. Another method for determining operative risk in patients with cirrhosis is the Model for End-Stage Liver Disease (MELD), which takes into account the patient’s prothrombin time, bilirubin, and creatinine with various iterations used to better predict perioperative morbidity and mortality (273,274). Originally designed to predict outcomes in cirrhotic patients undergoing the transjugular intrahepatic portosystemic shunt (TIPS) procedure, it was further studied to include patients undergoing other surgical procedures. In patients with a MELD score greater than 15, elective surgery should be deferred (275).
Acute Viral Hepatitis
Acute viral hepatitis poses an increased risk of operative complications and perioperative mortality and is a contraindication for elective surgery (276). Elective surgery should be delayed for approximately 1 month after the results of all biochemical tests have returned to normal (277). In patients with ectopic pregnancy, hemorrhage, or bowel obstruction secondary to malignancy, surgical intervention must take place before normalization of serum transaminase levels (276). In these situations, the perioperative morbidity (12%) and mortality (9.5%) rates are much higher than when they are performed under ideal situations (269).
Chronic Hepatitis
Chronic hepatitis is a group of disorders characterized by inflammation of the liver for at least 6 months. The disease is divided by morphologic and clinical criteria into chronic persistent hepatitis and chronic active hepatitis. A liver biopsy is usually required to establish the extent and type of injury. The surgical risk in these patients correlates most closely with the severity of disease. The risk of surgery in patients with asymptomatic or mild disease is minimal in contrast to a significant risk for those patients who have symptomatic chronic active hepatitis (278). Elective surgery is contraindicated in symptomatic patients, and nonelective surgery is associated with significant morbidity (277). In the nonelective situation, patients taking long-term glucocorticoid therapy should be given appropriate stress coverage with a higher dose of glucocorticoids during the perioperative period. Preoperatively, patients who are not taking steroids should receive prednisone and azathioprine, which are shown to reduce the perioperative risk of complications and may result in remission in as many as 80% of patients (279). Asymptomatic carriers of the hepatitis B virus (HBV; individuals who test positive for the HBV surface antigen) are not at increased risk for postoperative complications in the absence of elevated aminotransferase levels and liver inflammation.There is a significant risk to the health care professional operating on these individuals. In cases of needlestick in which the patient’s hepatitis status is unknown, both the health care worker and the patient should be tested for hepatitis C virus (HCV) antibody and HBV serologic markers. If markers for HBV infection are present, hepatitis B immune globulin should be administered to unvaccinated medical personnel. A vaccination series should be initiated during the early postoperative period. If the health care worker is immune (surface antibody positive), no treatment is necessary (269). All medical personnel, and especially those in the surgical subspecialties, should receive a full course of recombinant hepatitis B vaccine as recommended by the CDC (280). Treatment for chronic hepatitis B in the 1990s centered around interferon-α with data in the 2000s showing increased benefit from the use of nucleoside analogues, including lamivudine and tenofovir (281,282). Pegylated interferon and ribavirin are used in the standard treatment of HCV (283). Consideration should be given to using these medications for patients in whom surgery cannot be avoided but is not emergent.
Alcoholic Liver Disease
Alcoholic liver disease encompasses a spectrum of diseases including fatty liver, acute alcoholic hepatitis, and cirrhosis. Elective surgery is not contraindicated in patients with fatty liver because liver function is preserved. If nutritional deficiencies are discovered, they should be corrected before elective surgery. Acute alcoholic hepatitis is characterized on biopsy by hepatocyte edema, polymorphonuclear leukocyte infiltration, necrosis, and the presence of Mallory bodies. Elective surgery in these patients is contraindicated (284). Abstinence from alcohol for approximately 6 to 12 weeks along with clinical resolution of the biochemical abnormalities are recommended before surgery is considered. Severe alcoholic hepatitis may persist for several months despite abstinence and, if any question of continued activity exists, a liver biopsy should be repeated (285). In cases of urgent or emergent surgery on patients with alcohol dependence, administration of tapered doses of benzodiazepine is appropriate as prophylaxis against alcohol withdrawal.
Cirrhosis
Cirrhosis is an irreversible liver lesion characterized histologically by parenchymal necrosis, nodular degeneration, fibrosis, and a disorganization of hepatic lobular architecture. The most serious complication of cirrhosis is portal venous hypertension, which ultimately leads to bleeding from esophageal varices, ascites, and hepatic encephalopathy. Conventional liver biochemical test results correlate poorly with the degree of liver impairment in patients with cirrhosis. Hepatic dysfunction, may be somewhat quantified by low albumin levels and prolonged prothrombin times.
Surgical risk is increased in patients with advanced liver disease, although it is substantially greater in emergency surgery than in elective surgery. Perioperative mortality correlates with the severity of cirrhosis and can be estimated through the use of the Child’s classification (Table 22.21). In patients with Child’s class A cirrhosis, surgery can usually be performed without significant risk, whereas in patients with Child’s class B or C, surgery poses a major risk and requires careful preoperative consideration. Preoperative preparation should include the following measures: (i) optimizing nutritional status by enteral and parenteral nutrition and supplementation with vitamin B1, (ii) correcting coagulopathy with administration of FFP or cryoprecipitate or both, (iii) minimizing preexisting encephalopathy, (iv) preventing sepsis from spontaneous bacterial peritonitis by administering prophylactic antibiotic therapy, and (v) optimizing renal function and carefully correcting electrolyte abnormalities (286). Meticulous preoperative preparation focused on correcting abnormalities associated with advanced liver disease may improve surgical outcomes (287).
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