Handbook of Clinical Anesthesia
Ambulatory surgery is popular both for patients and those who own the facility (Lichtor JL: Anesthesia for ambulatory surgery. In Clinical Anesthesia. Edited by Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC. Philadelphia: Lippincott Williams & Wilkins, 2009, pp 833–846).
- Place, Procedures, and Patient Selection
- Ambulatory surgery occurs in a variety of settings (hospitals, freestanding satellite facilities, physician's offices).
- The Centers for Medicare and Medicaid Services (CMS) generally pays ambulatory centers 65% of what hospital outpatient surgical facilities receive.
- Procedures appropriate for ambulatory surgery are those associated with postoperative care that is easily managed at home and with low rates of complications that require intensive physician or nursing management.
- Scoring systems have been developed to help determine the likelihood of hospital admission after ambulatory surgery (older than 65 years, operating times longer than 120 minutes, regional anesthesia).
- Many facilities set a 4-hour limit as a criterion for performing a procedure.
- The need for a transfusion is not a contraindication for ambulatory procedures. Some patients undergoing liposuction as outpatients are given autologous blood.
- Infants whose postconceptual age is less than 46 weeks or whose age is less than 60 weeks but who also have a history of chronic lung or neurologic disease or have anemia (hemoglobin <6 mmol/L) should be monitored for 12 hours after the procedure because they are at risk of developing apnea even
without a history of apnea. Infants older than 46 weeks and younger than 60 weeks without disease should be monitored for 6 hours after the procedure.
- Advanced age alone is not a reason to disallow surgery in an ambulatory setting. Age, however, does affect the pharmacokinetics of drugs. Even short-acting drugs such as midazolam and propofol have decreased clearance in older individuals.
- Hospital admission by itself is not necessarily bad if it results in a better quality of care or uncovers the need for more extensive surgery.
- Obese patients are not more likely to have adverse outcomes, but they have a higher incidence of obstructive sleep apnea (OSA). The American Society of Anesthesiologists (ASA) has published practice guidelines for the perioperative management of patients with OSA.
- Patients who undergo ambulatory surgery should have someone to take them home and stay with them afterward to provide care.
- After the patient has returned home, he or she must be able to tolerate the pain from the procedure, assuming adequate pain therapy is provided.
- Patients undergoing certain procedures, such as laparoscopic cholecystectomy or transurethral resection of the prostate, should live close to the ambulatory facility because postoperative complications may require their prompt return.
- Preoperative Evaluation and Reduction of Patient Anxiety
Each outpatient facility should develop its own method of preoperative screening to be conducted before the day of surgery (history, medications, previous anesthetics, transportation and child care needs, dietary restrictions, attire, arrival times, laboratory tests). The preoperative screening is the ideal time for the anesthesiologist to talk with the patient. Automated history taking may also prove beneficial during the screening of a patient.
- Upper Respiratory Tract Infection
- Airflow obstruction has been shown to persist for up to 6 weeks after viral respiratory infections in adults. For this reason, surgery should be delayed if an adult presents with an upper respiratory infection (URI) until 6 weeks have elapsed.
Figure 32-1. Adverse respiratory events are similar between children with an upper respiratory infection (URI) and a recent URI, and this similarity persists for at least 4 weeks after the URI. *P < .05 versus no URI. (Reprinted with permission from Tait AR, Malviya S, Voepel-Lewis T, et al: Risk factors for perioperative adverse respiratory events in children with upper respiratory tract infections. Anesthesiology 95:299, 2001.)
- In the case of children, whether surgery should be delayed for this length of time is questionable. There seems to be no difference in the incidence of laryngospasm or bronchospasm if the child has had active URIs, a URI within 4 weeks, or no symptoms (Fig. 32-1). Children with active or recent URIs have more episodes of breathholding, incidences of desaturation below 90%, and more respiratory events compared with children without symptoms (Table 32-1).
- Although surgery may be canceled because a child is symptomatic, the child may develop another URI when the procedure is rescheduled.
Table 32-1 Independent Risk Factors for Adverse Respiratory Events in Children with Upper Respiratory Tract Infections
- Generally, if a patient with a URI has a normal appetite, does not have a fever or an elevated respiratory rate, and does not appear toxic, it is probably safe to proceed with the planned procedure.
- Restriction of Food and Liquids Before Ambulatory Surgery
- To decrease the risk of aspiration of gastric contents, patients are routinely asked not to eat or drink anything for at least 6 to 8 hours before surgery.
- Prolonged fasting can be detrimental to patients. Infants who fast longer have greater decreases in intraoperative blood pressure (Fig. 32-2).
- No trial has shown that a shortened fluid fast increases the risk of aspiration. Gastric volumes are actually lower when patients are allowed to drink some fluids before surgery.
- ASA practice guidelines for preoperative fasting allow a patient to have a light meal up to 6 hours before an elective procedure and support a fasting period for
clear liquids of 2 hours for all patients (including taking chronic medications). Coffee and tea are considered clear liquids.
Figure 32-2. Blood pressure is lower in children 1 to 6 months of age who fast more than 8 hours compared with those who fast for less than 4 hours. *P < .05 versus 0- to 4-hour fasting group. (Reprinted with permission from Friesen RH, Wurl JL, Friesen RM: Duration of preoperative fast correlates with arterial blood pressure response to halothane in infants. Anesth Analg 95:1572, 2002.)
- Coffee or tea drinkers should follow fasting guidelines but should be encouraged to drink coffee before the procedure because physical signs of caffeine withdrawal (headache) can easily occur.
- It is not clear if these fasting guidelines should apply to patients with diabetes or dyspepsia.
- Anxiety Reduction
- Preoperative reassurance from non-anesthesia staff and the use of booklets reduce preoperative anxiety. However, the use of booklets is less effective than a preoperative visit by the anesthesiologist. Audiovisual instructions also reduce preoperative anxiety.
- Much of a child's anxiety before surgery concerns separation from the parent or parents. If the parents are calm and can effectively manage the physical transfer to a friendly and playful anesthesiologist or nurse, premedication may not be necessary.
- Family-centered care (videotapes, pamphlets, mask practice kits) has become popular and is useful for decreasing children's preoperative anxiety.
III. Managing the Anesthetic: Premedication
Premedication is useful for controlling anxiety; reducing the risk of aspiration during induction of anesthesia; and controlling postoperative pain, nausea, and vomiting. Because outpatients go home on the day of surgery, the drugs given before anesthesia should not hinder their recovery.
- Midazolam is the benzodiazepine most commonly used preoperatively. For children, oral midazolam in doses as small as 0.25 mg/kg produces effective sedation and reduces anxiety. With this dose, most children can be effectively separated from their parents after 10 minutes, and satisfactory sedation can be maintained for 45 minutes. Discharge may be delayed, though, when midazolam is given before a short procedure.
- Routine administration of supplemental oxygen with or without continuous monitoring of arterial
oxygenation is recommended whenever benzodiazepines are given intravenously (IV).
- The potential for anterograde amnesia after premedication is a concern, especially for patients undergoing ambulatory surgery.
- Opioids and Nonsteroidal Analgesics
- Opioids may be administered preoperatively to sedate patients, control hypertension during tracheal intubation, and decrease pain before surgery. Meperidine (but not morphine or fentanyl) is sometimes helpful in controlling shivering in the operating room or postanesthesia care unit (PACU).
- Preoperative administration of opioids or nonsteroidal antiinflammatory drugs may be useful for controlling pain in the early postoperative period.
- Intraoperative Management: Choice of Anesthetic Method
- General anesthesia, regional anesthesia, and local anesthesia are equally safe.
- Even for experienced anesthesiologists, a failure rate is associated with regional anesthesia (Fig. 32-3).
- Some procedures are possible only with a general anesthetic. For others, the preferences of the patient, surgeon, or anesthesiologist may determine selection.
- Time to recovery may also influence the choice of anesthetic method (Fig. 32-4).
- One adverse effect associated with spinal anesthesia is headache, but headaches may also be experienced by patients after general anesthesia.
- Regional techniquescommonly used for ambulatory surgery, in addition to spinal and epidural anesthesia, include local infiltration, brachial plexus and other peripheral nerve blocks, and IV regional anesthesia.
- Performing a block takes longer than inducing general anesthesia, and the incidence of failure is higher (see Fig. 32-3).
- Unnecessary delays can be obviated by performing the block beforehand in a preoperative holding area.
- Postoperative pain control is best with regional techniques. Patients may still have a numb extremity (after a brachial plexus block) but otherwise meet all criteria for discharge. In such instances, the extremity must be well protected (sling for an upper extremity
procedure), and patients must be cautioned to protect against injury because they are without normal sensations that would warn them of vulnerability. Reassurance that sensation will return should be provided.
Figure 32-3. Operating room (OR) delays are the major reasons orthopedic surgeons do not favor regional anesthesia. GA = general anesthesia. (Reprinted with permission from Oldman M, McCartney CJ, Leung A, et al: A survey of orthopedic surgeons' attitudes and knowledge regarding regional anesthesia. Anesth Analg 98:1486, 2004.)
- Spinal Anesthesia
- Children.Spinal anesthesia is used in some centers, particularly for children undergoing inguinal hernia repair.
- Adults.The use of pencil point spinal needles with noncutting tips has prompted a resurgence of spinal anesthesia for ambulatory surgery in adults. Motor block of the legs may delay a patient's ability to walk. However, the use of a short-acting local anesthetic minimizes this problem. Nausea is much less frequent after epidural or spinal anesthesia than after general anesthesia.
- Lidocaine and mepivacaine are ideal for ambulatory surgery because of their short durations of action,
although lidocaine use has been problematic because of transient neurologic symptoms. Although transient neurologic symptoms may be seen after administration of other local anesthetics, the risk is seven times higher after intrathecal lidocaine administration than after bupivacaine, prilocaine, or procaine administration.
Figure 32-4. Recovery was faster when an infraclavicular brachial plexus block with a short-acting local anesthetic was used compared with general anesthesia and wound infiltration for outpatients undergoing hand and wrist surgery. Times are calculated from the end of anesthesia. (Reprinted with permission from Hadzic A, Arliss J, Kerimoglu B, et al: A comparison of infraclavicular nerve block versus general anesthesia for hand and wrist day-case surgeries. Anesthesiology 101:127, 2004.)
- Chloroprocaine spinal anesthesia has a rapid onset and offset.
- Ropivacaine and bupivacaine have been used for ambulatory surgical procedures, but the recovery times are relatively long.
- Although headache is a common complication of lumbar puncture, smaller-gauge needles result in a lower incidence of postdural puncture headache.
- For patients who receive spinal anesthesia, it is incumbent on the anesthesiologist and the facility to follow up with telephone calls to ensure no disabling symptoms of headache have developed.
- If the headache does not respond to bed rest, analgesics, and oral hydration, the patient must return to the hospital for a course of IV caffeine therapy or an immediate epidural blood patch.
- Bed rest does not reduce the frequency of headache; early ambulation may decrease the incidence.
- Epidural and Caudal Anesthesia
- Epidural anesthesia takes longer to perform than spinal anesthesia. Onset with spinal anesthesia is more rapid, although recovery may be the same with either technique.
- Caudal anesthesia is a form of epidural anesthesia commonly used in children before surgery below the umbilicus as a supplement to general anesthesia and to control postoperative pain.
- Bupivacaine 0.175 to 0.25% or ropivacaine 0.2% in a volume of 0.5 to 1.0 mL/kg may be used; a safe maximal dose is 2.5 mg/kg. When added to the anesthetic solution, epinephrine 1:200,000 may allow earlier detection of IV, rather than epidural, injection.
- The block is usually administered while the child is anesthetized. After injection, the depth of general anesthesia can be reduced.
- Because of better pain control after a caudal block, children can usually ambulate earlier and be discharged sooner than without a caudal block.
- Nerve Blocks
- There is widespread use of axillary and interscalene blocks for surgery in the upper extremity and ankle and femoral blocks for lower extremity surgery.
- Nerve blocks improve postoperative patient satisfaction because of lower levels of postoperative nausea, vomiting, and pain. Costs are also lower.
- Sedation and Analgesia
- Many patients who undergo surgery with local or regional anesthesia prefer to be sedated and to have no recollection of the procedure. Sedation is important, in part, because injection with local anesthetics can be painful and lying on a hard operating room table can be uncomfortable.
- Levels of sedation vary from light, during which a patient's consciousness is minimally depressed, to very deep, in which protective reflexes are partially blocked and response to physical stimulation or verbal commands may not be appropriate.
- Children who have surgery usually will not remain immobile unless they are deeply sedated or receive general anesthesia.
- General Anesthesia.Drugs selected for general anesthesia determine how long patients stay in the PACU after surgery, and for some patients, whether they can be discharged to go home.
- The popularity of propofol as an induction agent for outpatient surgery partly relates to its half-life. (Impairment after thiopental administration may be apparent for up to 5 hours but only for 1 hour after propofol administration.) Pain on injection can be a problem with propofol. Thrombophlebitis does not appear to be a problem after IV administration of this agent, but it can be evident after thiopental administration. IV lidocaine 0.2 mg/kg may be used to decrease the incidence and severity of pain.
- Sevoflurane has a relatively low blood–gas partition coefficient, and the speed of induction is similar to, albeit somewhat slower than, that of propofol. Induction with sevoflurane can be hastened when the patient is told to breathe out to residual volume, take a vital capacity breath through a primed anesthesia circuit, and then hold the breath.
- For short procedures, some patients may not require neuromuscular blocking drugs, but others may need brief paralysis with succinylcholine (Sch) to facilitate tracheal intubation. Nondepolarizing drugs such as rocuronium have rapid onset times that are similar to those of Sch. Sch should be used with caution in children because of the possibility of cardiac arrest related to malignant hyperthermia or unsuspected muscular dystrophy, particularly Duchenne muscular dystrophy.
- Maintenance.Although many factors affect the choice of agents for maintenance of anesthesia, two primary concerns for ambulatory anesthesia are speed of wake-up and the incidence of postoperative nausea and vomiting.
- Anesthesia Maintenance and Wake-Up Times.Time to recovery may be measured by various criteria. However, actual discharge from an ambulatory center may depend on administrative issues,
such as a written order from a surgeon or anesthesiologist. Sevoflurane, unlike desflurane, facilitates a smooth inhalation induction of anesthesia and is the preferred technique for ensuring rapid recovery of children in ambulatory surgery centers. It is important to distinguish between wake-up time and discharge time.
- Intraoperative Management of Postoperative Nausea and Vomiting.Nausea, with or without vomiting, is probably the most important factor contributing to a delay in discharge of patients and an increase in unanticipated admissions of both children and adults after ambulatory surgery (Table 32-2).
- Receptor antagonists (selective serotonin antagonists such as ondansetron, dolasetron, and granisetron) have been shown to have similar efficacy to help alleviate nausea and vomiting. Dopamine antagonists, antihistamines, and anticholinergic drugs are useful and are generally less expensive but are associated with extensive side effects.
- Combination therapy is probably the most effective way to control postoperative nausea and vomiting (Table 32-3).
- Paralysis.Reversal agents must be used unless there is no doubt that muscle relaxation has been fully reversed.
- Intraoperative Management of Postoperative Pain
- When given intraoperatively, opioids (most commonly fentanyl) are useful for supplementing both intraoperative and postoperative analgesia.
Table 32-2 Patients at Greatest Risk for Postoperative Nausea and Vomiting
Table 32-3 Approaches for Reducing the Incidence of Postoperative Nausea and Vomiting
- All opioids may cause nausea, sedation, and dizziness, which may delay a patient's discharge.
- Nonsteroidal analgesics are not effective as supplements during general anesthesia, although they are useful in controlling postoperative pain, particularly when given before skin incision.
- Depth of Anesthesia.Use of bispectral index (BIS) and entropy or auditory-evoked potential monitors can decrease anesthesia requirements without sacrificing amnesia during general anesthesia.
- Airways.The use of a laryngeal mask airway or similar type of airway provides several advantages for allowing a patient to return quickly to baseline status (Table 32-4).
- Management of Postanesthesia Care
The three most common reasons for delay in patient discharge from the PACU are drowsiness, nausea and vomiting, and pain.
- Reversal of Drug Effects
- Reversal of opioids may sometimes be necessary.
- Flumazenil, a benzodiazepine receptor antagonist, has primarily been used to reverse the effects of sedation after endoscopy and spinal anesthesia.
Table 32-4 Advantages of Laryngeal Mask Airways
- Nausea and vomitingare the most common reasons both children and adults have protracted stays in the PACU or unexpected hospital admission after anesthesia. A variety of drugs are effective in treating the problem (5-HT3 antagonists seem particularly effective). Midazolam and propofol, although more commonly used for sedation, have antiemetic effects that are longer in duration than their sedative effects.
- Pain.Postsurgical pain must be treated quickly and effectively. It is important for the practitioner to differentiate postsurgical pain from the discomfort of hypoxemia, hypercapnia, or a full bladder.
- Medications for pain control should be given in small IV doses (1 to 3 mg/70 kg of morphine or 10 to 25 µg/70 kg of fentanyl).
- Nonsteroidal medications, such as ketorolac or ibuprofen, can also effectively control postoperative pain and, compared with opioids, can give pain relief for a longer period and are associated with less nausea and vomiting.
- Preparation for Discharging the Patient
- In addition to the PACU, many ambulatory surgery centers have a phase II recovery room, where patients may stay until they are able to tolerate liquids, walk, and void.
- Patients who undergo procedures under monitored anesthesia care can usually go straight to the phase II area from the operating room.
- Some criteria for discharge to home were created without scientific basis. One criterion is the ability to tolerate liquids before being discharged. Postoperative nausea may be greater if patients are required to drink liquids before discharge. Even though it is warranted after spinal or epidural anesthesia, the requirement that low-risk patients void before discharge may only lengthen the hospital stay, particularly if the patient is willing to return to a medical facility if he or she is unable to void.
- Patients may feel fine after they leave the hospital, but they should be advised against driving for at least 24 hours after a procedure.
- Patients should also be informed that they may experience pain, headache, nausea, vomiting, or dizziness and, if Sch was used, muscle aches and pains apart from the incision for at least 24 hours.
- Anesthesia for ambulatory surgery is a rapidly evolving specialty. Patients once believed unsuitable for ambulatory surgery are now considered to be appropriate candidates. Operations once believed unsuitable for outpatients are now routinely performed in the morning so patients can be discharged in the afternoon or evening. The availability of both shorter-acting anesthetics and longer-acting analgesics and antiemetics enables us to care effectively for patients in ambulatory centers.
Editors: Barash, Paul G.; Cullen, Bruce F.; Stoelting, Robert K.; Cahalan, Michael K.; Stock, M. Christine
Title: Handbook of Clinical Anesthesia, 6th Edition
Copyright ©2009 Lippincott Williams & Wilkins
> Table of Contents > Section VI - Anesthetic Management > Chapter 33 - Office-Based Anesthesia