Peter Pompei MD
ASSESSING & MANAGING PREOPERATIVE RISK FACTORS
Cardiovascular problems, respiratory compromise, and neuropsychiatric changes are among the most common and serious complications of operative therapies in older patients.
A number of different cardiac risk indexes have been developed for patients undergoing noncardiac surgery. These have been useful for stratifying patients according to their risk of cardiac complications based on information gathered preoperatively from their history, physical examination, and laboratory test results. Although quantifying the likelihood of cardiac complications can be useful to the physician by focusing attention on those patients at highest risk, it may be even more useful to have evidence-based direction on the optimal management of the identified problems.
A practice guideline has been developed by the American College of Cardiology and the American Heart Association (Figure 9-1). Step 1 asks the clinician to clarify the urgency of the procedure. Step 2 calls for knowledge of any previous coronary revascularization. In Step 3, clinical predictors culled from many studies have been divided into 3 levels of importance: minor, intermediate, and major. Advanced age is only a minor clinical predictor; rather, the presence of accumulated medical problems more strongly increases operative risk among older persons. For patients who have intermediate or minor clinical predictors, it is important to consider functional capacity (Steps 6 and 7). Patients should be asked whether they can do more than light household work (dusting or washing dishes), such as climbing a flight of stairs, walking up a hill, and walking on level ground at 4 mph (6.4 km/h). These activities are associated with more than 4 metabolic equivalents, and patients who can exert themselves to this degree are judged to have at least a moderately good functional capacity. As also shown in Steps 6 and 7, the assessment of intrinsic procedural risk will influence recommendations regarding preoperative management.
High-risk procedures include emergent major operations, aortic and other vascular surgery, and prolonged procedures with large fluid shifts or blood loss. Examples of intermediate risk procedures are carotid endarterectomy, head and neck surgery, and intraperitoneal, thoracic, orthopedic, and prostate operations. Common low-risk procedures are cataract and breast surgery and endoscopic procedures.
Additional evaluation and management are recommended for all patients with major clinical predictors before operative therapy. Noninvasive cardiac testing is recommended before operative therapy for patients with intermediate clinical predictors and poor functional status or moderate to excellent functional status if the planned procedure is high risk. Noninvasive cardiac testing is also recommended for patients with no or minor clinical predictors who have a poor functional status and are scheduled for a high-risk procedure. Like other practice guidelines, this one is intended to assist physicians in meeting the needs of most patients in the majority of circumstances, and final decisions regarding an individual patient should be made jointly by the treating physician and the patient.
Pulmonary complications are also common among older persons undergoing operative therapies. This is due to age-related changes in the respiratory system and to the effects of anesthesia and surgery on the lungs. Advancing age is associated with reduced alveolar elasticity and increased chest wall stiffness, changes that can predispose to atelectasis and decreased expiratory flow rates. The supine position, general anesthetic agents, and abdominal incisions contribute to reduced functional residual capacity and increased airway resistance. Resultant hypoventilation and atelectasis may cause hypoxemia and infection. Identifying patients at high risk for respiratory decompensation is a first step in attempting to reduce the complication rate.
Several characteristics identify patients at increased risk for pulmonary complications: impaired cognitive function, body mass index of ≥27 kg/m2, chest wall or upper abdomen incision, smoking within the past 8 weeks, age ≥60 years, a history of cancer, a history of angina, an incision length ≥30 cm, and an American
Society of Anesthesiologists rating of class III or greater. More work is needed to establish a valid risk index that can serve as the basis for a practice guideline. Beyond identifying those patients at greatest risk for pulmonary complications, the physician has an important role to play in encouraging coughing, deep breathing exercises, incentive spirometry, and early mobility to further reduce the risk of respiratory problems.
Figure 9-1. Algorithm for the preoperative assessment and management of patients with known or suspected cardiac disease. CHF, congestive heart failure; ECG, electrocardiogram; MET, metabolic equivalent; MI, myocardial infarction. From Eagle KA et al: ACC/AHA guideline update for perioperative cardiovascular evaluation for noncardiac surgery: A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. American College of Cardiology, 2002. Used with permission.
Neuropsychiatric problems such as dementia and depression are common among older patients and can contribute to poor outcomes after surgery. The most common postoperative neuropsychiatric complication is delirium. Both preoperative and intraoperative factors have been evaluated as risk factors for delirium. Factors that predispose an individual to postoperative delirium after noncardiac surgery are age ≥70 years; cognitive impairment; limited physical function; history of alcohol abuse; abnormal serum sodium, potassium, or glucose; intrathoracic surgery; and abdominal aneurysm surgery. Type of anesthesia and intraoperative hypotension, bradycardia, and tachycardia are not associated with delirium. Patients with a postoperative hematocrit <30% have an increased risk of delirium. Clinicians caring for patients at greatest risk of delirium should focus management on correcting fluid, electrolyte, and metabolic derangements and optimizing replacement of blood loss.
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Gilbert K et al: Prospective evaluation of cardiac risk indices for patients undergoing noncardiac surgery. Ann Intern Med 2000; 133:356.
Marcantonio ER et al: The association of intraoperative factors with the development of postoperative delirium. Am J Med 1998;105:380.
Eagle KA et al: ACC/AHA guideline update for perioperative cardiovascular evaluation for noncardiac surgery: A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to update the 1996 guidelines on perioperative cardiovascular evaluation for noncardiac surgery): http://www.acc.org/clinical/guidelines/perio/clean/perio_index.htm
PERIOPERATIVE MANAGEMENT OF SELECTED MEDICAL PROBLEMS
Several medical conditions commonly encountered in older persons deserve special attention during the perioperative period. For some of these, changes in therapy are warranted preoperatively; for others, aggressive perioperative management is critical to reduce the risk of complications.
Hypertension is among the most common chronic medical problems among older persons and is associated with an increased risk of stroke, myocardial infarction, and renal insufficiency. Perioperative myocardial ischemia is related not only to uncontrolled preoperative hypertension but also to major fluctuations in blood pressure during the procedure. This variability can be related to the effects of anesthetic agents, stimulation of the sympathetic and parasympathetic pathways, and changes in intravascular volume. Patients with chronic hypertension should have their blood pressure well controlled before any procedure, and elective procedures should be postponed if the preoperative blood pressure is >180/110 mm Hg. Oral antihypertensives should be given with a sip of water on the day of operation and restarted as soon as possible postoperatively. When the blood pressure is elevated postoperatively, secondary causes such as pain or a distended bladder should first be investigated. Parenteral medications that are useful in controlling essential hypertension in older persons after operations include β-blockers, calcium channel blockers, angiotensin-converting enzyme (ACE) inhibitors, and drugs that block both α- and β-adrenergic receptors. Vasodilators such as hydralazine should be used with caution because of the risk of compromising diastolic filling if there is hypertrophic cardiomyopathy related to chronic hypertension.
The administration of β-blockers perioperatively to patients with known or suspected coronary artery disease has been shown to reduce the risk of cardiac complications.
Patients at increased risk for stroke are those with known cerebral or peripheral vascular disease and chronic obstructive pulmonary disease. Patients who have experienced transient ischemic attacks should be evaluated for carotid stenosis. If a carotid endarterectomy is indicated, this should be done before elective noncardiac surgery.
Congestive Heart Failure
Patients in decompensated heart failure should have elective procedures postponed. Drug regimens that should
be continued perioperatively generally include β-blockers, ACE inhibitors, and diuretics. Optimizing ventricular filling pressures is key, and it is often difficult to accurately assess volume status in older persons by physical examination and standard laboratory parameters. Swan-Ganz catheters and transesophageal echocardiography have substantially improved our ability to monitor cardiac output and optimize volume management.
Valvular Heart Disease
The greatest risks associated with valvular heart disease include congestive heart failure and endocarditis. Asymptomatic aortic stenosis leading to myocardial ischemia or congestive heart failure can be difficult to distinguish from the more benign aortic sclerosis common in older persons. A bedside prediction rule to identify moderate or severe aortic stenosis is to listen for a systolic murmur over the right clavicle. If absent, significant aortic stenosis is unlikely; if present, the patient should be examined for reduced carotid artery volume, slow carotid artery upstroke, reduced intensity of the second heart sound, and maximum intensity of the murmur over the second right intercostal space. If 3 of these 4 findings are present, there is a significant risk of aortic stenosis, which can be confirmed by echocardiogram. Selected valvular and other cardiac conditions predispose patients to the risk of endocarditis, for which prophylactic antibiotics are indicated. Patients with prosthetic cardiac valves, complex congenital heart disease, and surgically constructed systemic-pulmonary shunts or conduits or a history of endocarditis are at highest risk. Patients at moderate risk are those with other congenital cardiac malformations, acquired valvular dysfunction, hypertrophic cardiomyopathy, mitral valve prolapse with regurgitation, or thickened leaflets. Patients undergoing procedures that involve the respiratory, biliary, or intestinal mucosa, prostate surgery, cystoscopy, or urethral dilation should be given endocarditis prophylaxis. Recommended antibiotic regimens according to procedure and patient risk category are shown in Table 9-1.
Cardiac Rhythm Disturbances
Cardiac rhythm disturbances can increase the risk of myocardial ischemia and congestive heart failure. Older persons are at increased risk for supraventricular tachycardias, especially those with a history of a supraventricular dysrhythmia, asthma, congestive heart failure, and premature atrial complexes on a preoperative electrocardiogram and those undergoing vascular, abdominal, or thoracic procedures.
It is important to try to restore sinus rhythm with infusions of adenosine or to control ventricular rate with a β-blocker or a calcium channel blocker. Atrial fibrillation is especially common after cardiac surgery, and prophylactic β-blockers should be used in all patients unless contraindicated. When atrial fibrillation develops postoperatively, conversion to sinus rhythm can be attempted with electrical cardioversion or amiodarone. Otherwise, the rate can be controlled with β-blockers or calcium channel blockers, and spontaneous reversion to sinus rhythm often occurs within 6 weeks. Patients with atrial fibrillation for more than 24-48 h should be treated with anticoagulation therapy to reduce the risk of stroke.
Smoking cessation is a key intervention in reducing the risk of postoperative pulmonary complications. Unfortunately, abstinence for several weeks may be necessary to see significant improvements in small airway disease, hypersecretion of mucus, and tracheobronchial clearance. Other interventions, such as antibiotics, chest physiotherapy, incentive spirometry, and supplemental oxygen have been reported to improve selected outcomes. No evidence-based guideline is available to direct management of patients at risk for pulmonary complications. Expert consensus is to encourage smoking cessation, consider adjunctive chest physiotherapy (deep-breathing exercises, chest percussion, and incentive spirometry), and use antibiotics for patients with infected sputum and bronchodilators and steroids for those with bronchospasm.
Thromboembolic complications are common during the perioperative period, the most serious of which is pulmonary embolism. Venous thrombosis and pulmonary emboli can be difficult to treat effectively, and attention is focused on prophylaxis. For patients older than 60 who are undergoing general surgery, current recommendations are for thrombosis prophylaxis with low-dose unfractionated heparin, low-molecular-weight heparin, or intermittent pneumatic compression devices. For patients undergoing elective hip or knee replacement or hip fracture surgery, low-molecular-weight heparin or adjusted-dose coumadin (INR target 2.5, range 2-3) are acceptable alternatives.
RENAL & ELECTROLYTE DISORDERS
Impaired renal function increases the risk of postoperative renal failure. This can be due to compromised cardiac output and exposure to nephrotoxic medications. The early signs of acute renal failure are oliguria, isosthenuria,
and a rising serum creatinine. If the cause of the renal failure is impaired renal blood flow, the urine sodium will typically be <40 mEq/L, and the urine-plasma creatinine ratio will be >10:1. In contrast, if acute tubular necrosis is present, there may be granular or epithelial cell casts in the urine sediment, the urine sodium will be >40 mEq/L, and the urine-plasma creatinine ratio will be <10:1.
Table 9-1. Prophylactic antibiotic regimens for patients at risk for bacterial endocarditis.
This syndrome requires aggressive management, including holding all nephrotoxic medications and meticulously maintaining a euvolemic state. Occasionally, dialysis may be necessary if hypervolemia, hyperkalemia, metabolic acidosis, or encephalopathy develops.
Obstructive nephropathy is a concern, especially in older men. Medications with anticholinergic effects may compromise detrusor function so that acute urinary retention develops.
Type 2 diabetes
Type 2 diabetes is prevalent among older persons and predisposes them to conditions for which operative interventions may be necessary. Patients with diabetes are at increased risk for infections and cardiovascular complications related to surgical procedures. The stress and tissue injury associated with surgery result in release of insulin counterregulatory factors such as epinephrine, glucagon, cortisol, and growth hormone. These stimulate gluconeogenesis or blunt insulin release or insulin action, resulting in hyperglycemia. In addition, the metabolism and clearance of insulin may be altered, and
nutritional intake can be quite variable during the perioperative period. All of these factors complicate the management of patients with diabetes whose glucose levels may vary widely.
Because the greatest risk of serious complications is from hypoglycemia, many clinicians accept a target blood sugar in the range of 150-200 mg/dL. Frequent monitoring of blood sugars is key in any management strategy; the blood sugar should be measured before administration of the anesthetic, during the procedure, and in the recovery room. The frequency of subsequent measures will depend in part on the level of control and the management strategy. If the patient has diet-controlled diabetes, no special preoperative interventions are required.
Perioperative hyperglycemia can be effectively managed with short-acting insulin administered subcutaneously. Patients treated with oral hypoglycemic agents should have the medication held on the day of operation, and hyperglycemia can be managed with short-acting insulin until the oral agent can be resumed. For patients receiving once-daily insulin injections, one half to two thirds the daily dose should be administered on the morning of surgery, and glucose-containing intravenous solutions should be administered at a rate delivering 5-10 g of glucose per hour. If multiple insulin injections are used to manage a patient's diabetes, one half to one third of the morning dose should be administered preoperatively, and glucose-containing intravenous solutions should be run at a constant rate. Fluctuations in blood sugar can continue for several days postoperatively, and patients must be instructed in adjusting their regimens at home as hospital stays have shortened.
Thyroidal diseases are not as common as diabetes but, if unrecognized and untreated, can result in significant postoperative complications.
Hypothyroidism is present in about 10% of hospitalized older patients. Because nonspecific and atypical manifestations are so common in older persons, it is important to maintain a high index of suspicion. Untreated hypothyroidism can slow drug metabolism and contribute to central nervous system depression and respiratory insufficiency. If rapid correction of hypothyroidism is indicated because of trauma or other emergency operations, one can safely administer 300-500 µg of l-thyroxine intravenously to improve the metabolic rate within 6 h. Stress-dose corticosteroids are commonly administered simultaneously to avoid depletion of adrenal reserves with a rapid increase in the basal metabolic rate.
Hyperthyroidism is much less common and occurs in fewer than 1% of hospitalized older patients. As with hypothyroidism, nonspecific and atypical clinical manifestations are common. If untreated, complications of fever, tachyarrhythmias, and congestive heart failure can result. Older patients may become hyperthyroid after nonionic contrast radiography. Restoration of a euthyroid state should be achieved before elective procedures. Emergency treatment with 1000 mg of propylthiouracil by mouth and a β-blocker to manage catecholamine surges is an option when an urgent operation is required. Again, stress-dose steroids are often given simultaneously to avoid cortisol depletion and to lower serum thyroxine and thyroid-stimulating hormone levels.
FLUID & NUTRITION MANAGEMENT
Body Composition & Fluid Regulation
Changes in body composition and fluid regulation complicate the management of older persons in the perioperative period. With aging, there is a relative increase in body fat and a reduction in muscle, total body water, and intracellular water. Thirst is blunted. The ability of the kidneys to concentrate the urine and conserve water may also decline. During the perioperative period, hormonal changes in response to the trauma of tissue injury predispose to extravascular fluid accumulation, and there is a risk of iatrogenic injury related to the administration of intravenous fluids.
The following recommendations guide calculation of fluid requirements. First, estimate the intracellular volume as percentage of body weight: 25-30% for men aged 65-85 and weighing 40-80 kg and 20-25% for women of the same age and weight ranges. Next, estimate the daily metabolic requirements per liter of intracellular volume (in the absence of acute stress and conditions that will affect salt and water balance) as follows: water, 100 mL; energy, 100 kcal; protein, 3 g; sodium, 3 mmol; potassium, 2 mmol. For example, a 75-year-old woman who weighs 60 kg has an estimated intracellular volume of 12 L. Her daily maintenance requirement for water would be 1.2 L or an administration rate of 50 mL/h. Careful monitoring of volume status is essential so that appropriate adjustments can be made based on patient response and changing conditions.
Nutritional issues are also important during the perioperative period when the demand for energy is increased
as a result of wound healing. Optimizing preoperative nutritional status is important, although the benefits of parenteral nutrition to achieve this goal have not been consistently demonstrated. A low serum albumin is an important marker for poor postoperative patient outcomes such as prolonged hospitalization and increased morbidity and mortality.
It is accepted practice to provide supplemental enteral nutrition to malnourished patients with a functioning gastrointestinal tract and to reserve parenteral nutrition for those patients in whom enteral feedings are not possible.
CHALLENGING POSTOPERATIVE SYNDROMES
Many of the conditions previously discussed require management throughout the perioperative period. After the operation, one important goal is to restore the patient to an optimal level of functioning. This will involve, among other things, early mobilization and resumption of as many self-care activities as possible. Avoiding prolonged bed rest will reduce the risk of thromboembolism, improve the respiratory mechanics, minimize cardiovascular deconditioning, and reduce muscle loss. Managing pain and cognitive impairment are other specific tasks during the postoperative period.
Postoperative pain is generally acute and time limited. Patient-controlled analgesic systems are now widely used. The degree of pain varies with the procedure and according to patient-specific factors. Each analgesic regimen must be tailored to the individual needs of the patient by frequently asking about pain and adjusting the pain regimen as necessary.
Not all patients will require narcotic analgesics. When narcotics are used, it is important to anticipate common adverse effects such as excessive sedation, fall risk, and constipation.
Older patients should be monitored postoperatively for at least 2 important syndromes of brain dysfunction: delirium and postoperative cognitive decline.
Delirium is a transient disorder characterized by abrupt onset, inattention, and altered consciousness. It occurs in 10-50% of older patients who undergo surgery and is associated with increased morbidity and mortality. Causes are varied, although metabolic derangements, drugs, infections, and cardiorespiratory disorders are commonly implicated.
Treatment is directed at correcting the underlying cause and supporting the patient through what can be a frightening experience. Drugs can be used when patients are at risk for harm as a result of the delirium. Low doses of major tranquilizers or atypical antipsychotics can be effective but should be used sparingly.
Postoperative Cognitive Decline
Postoperative cognitive decline is a separate, often subtle syndrome in which patients experience abnormalities in learning and memory. It is especially common after cardiac surgery and may persist for many months in 10-30% of patients. The cause is unknown; studies have not been able to demonstrate links with hypotension, hypoxemia, or type of anesthesia. Treatment is supportive until we have a better understanding of the causes this syndrome.
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