A 38-year-old woman is scheduled for diagnostic pelvic laparoscopy at 3 o’clock in the afternoon as an ambulatory procedure. She arrives at the ambulatory surgery center (ASC) 1 hour before scheduled surgery, accompanied by her 11-year-old son, and appears to be extremely apprehensive. Prior medical history is significant for asymptomatic gastroesophageal reflux disease; long-standing stable asthma that has been successfully treated with inhaled sympathomimetics and steroids; and type 1 diabetes mellitus, currently controlled with 25 units of neutral protamine Hagedorn (NPH) and 6 units of regular insulin every morning and 10 units of NPH and 3 units of regular insulin every night.
Are there advantages to performing surgery on an ambulatory basis?
There are multiple advantages to performing surgery on an ambulatory basis. First, patients return more quickly to the familiar home environment; this can be very important for both pediatric and geriatric surgical patients. A reduction in nosocomial infections has also been noted. Medication errors related to faulty prescribing or dispensing of drugs is decreased in ambulatory surgery.
Overall costs for ambulatory procedures are usually reduced. Cost savings are due to decreased laboratory testing, fewer medical consultations, and reduced numbers of pharmaceuticals dispensed. The significant expense of both the inpatient hospitalization and the hospital facility fee is avoided.
Other, less tangible advantages include ease of scheduling procedures and an improved sense of patient privacy because most ASCs are staffed by a small consistent group of personnel.
Which patients are considered acceptable candidates for ambulatory surgery?
Acceptable candidates for ambulatory surgery generally have relatively stable medical conditions. However, many centers now accept American Society of Anesthesiologists (ASA) physical statuses III and IV patients for selected, relatively noninvasive surgical procedures and diagnostic studies. Generally, less invasive surgery is performed on patients who are less healthy, whereas more invasive surgery is performed on ASA physical status I or II patients. Patients with cardiovascular disease have an increased risk of perioperative complications and may not be suitable candidates for invasive ambulatory procedures. Patients with severe physical or mental handicaps are often excluded from consideration as candidates for ambulatory surgery. Patients or caregivers must be able to comprehend and comply with postoperative instructions for successful ambulatory surgery.
Ambulatory surgery is well suited for pediatric patients. Generally, ambulatory surgical procedures performed on children are shorter in duration, less extensive, and less invasive than most procedures performed on adults. Additional benefits to pediatric patients include less disruption of the child’s normal feeding schedule and decreased separation time from parents. Exposure to the unfamiliar and frightening hospital milieu can be reduced to the bare minimum. Additionally, because recovery times are short for procedures such as myringotomy and tubes, circumcision, and inguinal herniorrhaphy, early discharge from the facility is feasible.
Preoperative communication and collaboration between anesthesiologists and surgeons are essential in the event of a questionable or problem patient. The surgeon who is to perform the procedure, the patient, and the family must be agreeable to the concept of ambulatory surgery. However, reimbursement schedules created by insurance carriers often convince the occasional skeptic because costs associated with hospitalization for procedures that can be readily performed on an ambulatory basis usually are not covered. Overwhelming and incontrovertible evidence of medical necessity for inpatient care must be presented to obtain authorization for postoperative hospitalization.
Are there patients who should never have surgery on an ambulatory basis?
Ex-preterm infants who are <55–60 weeks postconceptual age should not have ambulatory surgery. These infants are at risk for postoperative apnea and bradycardia for the next 12 hours (and may last up to 48 hours) after sedation and general anesthesia. In-hospital monitoring of ex-preterm infants is recommended postoperatively. For similar reasons, term infants <44 weeks postconceptual age should have surgery performed as inpatients. Postoperative respiratory monitoring is mandatory for at least 12–18 hours. If possible, surgery and diagnostic procedures requiring sedation or general anesthesia should be postponed until the child passes the unsafe period.
Are diabetic patients suitable candidates for ambulatory surgery?
Diabetic patients may present a major challenge for the anesthesiologist when scheduled for ambulatory surgery. Because of the critical nature of glucose homeostasis, it may be advisable to handle exceptionally brittle diabetics on an inpatient basis. Preoperatively, diabetic patients must be carefully assessed for the presence of end-organ damage. Cardiovascular disease, autonomic and renal insufficiency, and gastroparesis may lead to potential problems in the perioperative period.
It is preferable to schedule surgery for patients with type 1 diabetes as the first or second case of the day. The major concerns are to avoid the extremes of plasma glucose, both hypoglycemia and hyperglycemia, and acidosis. Delays in insulin administration may lead to ketoacidosis despite the fasting state. For this reason, it is recommended that patients receive insulin along with a continuous infusion of dextrose on arrival at the ASC. Insulin may be administered by either the subcutaneous or the intravenous route. The advantage of administering a continuous infusion of regular insulin versus one third to one half of the usual long-acting insulin dose subcutaneously has not been demonstrated. Another option for early-morning surgical procedures is to administer the usual long-acting insulin dose subcutaneously immediately after surgery and shift the time of all meals and future insulin injections by the same offset.
Patients receiving oral hypoglycemic agents must be carefully monitored in the perioperative period by finger-stick or blood glucose determinations. The half-life of some oral agents (e.g., chlorpropamide) may be 60 hours. Patients with type 2 diabetes mellitus rarely develop ketoacidosis. However, these patients can experience hyperosmolar, nonketotic coma when significant hyperglycemia and dehydration occur.
Before discharge, it is critical that diabetic patients are capable of eating. They also should be relatively free of nausea that might lead to emesis and inability to maintain adequate caloric intake.
What types of surgical procedures are appropriate for ambulatory surgery?
Initially, ambulatory surgery procedures were limited to 11⁄2 hours. The concern was for lengthy postanesthesi a recovery time that would extend beyond the facility’s hours of operation. However, newer anesthetic agents allow for safe discharges on a timely basis even after long procedures performed with general anesthesia.
The types of surgical procedures that may be performed on an ambulatory basis depend on whether an ASC is truly a freestanding unit (i.e., geographically detached from a hospital) or is located within a hospital or directly contiguous to an inpatient facility. Hospital-based units often accept patients with a greater severity of baseline illness and may perform more complex surgical procedures for many reasons. In the event of unexpected massive surgical hemorrhage, availability of immediate blood bank support is crucial and available in hospitals. However, when the need for blood may be anticipated preoperatively, freestanding ASCs can arrange for blood products to be available, and transfusions may be administered if the need arises. Patients may also be asked to donate one or more units of autologous blood, which may be kept available for intraoperative or postoperative use. Procedures in which blood might be administered include extensive liposuction or reduction mammoplasty. Radiology services, subspecialty consultative services, and the relative ease of hospital transfer for overnight admission allow performance of more involved and invasive procedures in hospital-based ASCs.
Ideal procedures for ambulatory surgery result in relatively minor postoperative physiologic changes including fluid shifts and blood loss. Commonly performed surgeries include procedures from all surgical disciplines and subspecialties. A few examples include cataract extraction; breast surgery; plastic surgery; gynecologic procedures such as dilation and curettage, hysteroscopy, termination of pregnancy, and laparoscopy; arthroscopy; and inguinal and umbilical herniorrhaphies. The common denominator of all these procedures is that they are associated with only mild to moderate degrees of postoperative pain, which may be readily controlled by oral analgesic agents.
In the early days of ambulatory surgery, a tonsillectomy was an example of a procedure that was considered to require overnight in-hospital observation. Today, tonsillectomy is being performed on an ambulatory basis in many centers, although the period of postoperative observation is increased compared with other ambulatory surgeries. After tonsillectomy, nausea and vomiting are the most common complications causing morbidity. Early bleeding, if it occurs, usually becomes evident within the first 6 hours. It is acceptable to discharge individuals to home who are otherwise in good health, reside within a reasonable distance from the facility, are accompanied by a responsible adult, and have successfully tolerated oral intake without nausea and vomiting. It is especially important that adequate fluid repletion is accomplished before discharge because early attempts at fluid intake by mouth after tonsillectomy may be unsuccessful as a result of pharyngeal pain.
What is the appropriate fasting time before ambulatory surgery that necessitates an anesthetic?
The preoperative fasting period prescribed for patient who will receive anesthesia is identical for inpatients and outpatients. The ASA fasting guidelines recommend 8 hours for solids, 6 hours for light meals (i.e., toast and tea), 4 hours for breast milk, and 2 hours for clear liquids. Ingestion of 8 oz. of orange juice without pulp or coffee without milk has not been shown to increase gastric volume. Both resting gastric volume and acidity may be reduced, which may decrease further the incidence and potentially devastating sequelae of intraoperative aspiration.
Other benefits result from decreasing the fasting time in patients preoperatively. Patients allowed to drink clear fluids are more content while waiting for surgical procedures that either were delayed or were scheduled later in the day. Thirst is relieved, and hunger may be diminished. Ingestion of glucose-containing solutions may also prevent relative degrees of hypoglycemia. Medications required for the maintenance of homeostasis, such as blood pressure and cardiac drugs, can be taken orally up to 1 hour before surgery with 1 oz. of water.
Fasting guidelines should not be made on a case-by-case basis but rather should be reflected in facility-wide or institution-wide guidelines.
Should drugs be administered to empty the stomach or change gastric acidity or volume before administering an anesthetic?
Studies regarding differences in resting gastric volume between inpatients and ambulatory patients have yielded conflicting results. No evidence supports the notion that every patient must receive liquid nonparticulate antacids (0.3 molar sodium citrate, 30 mL) before induction of anesthesia. A soluble (nonparticulate) antacid is substituted for the conventional nonabsorbable antacid containing aluminum, magnesium, or calcium hydroxide to avoid severe chemical pneumonitis that may result from aspiration of these particulate substances. Other pharmacologic agents include H 2 -receptor blockers (e.g., ranitidine, famotidine), which inhibit gastric acid production and decrease gastric volume. Mental confusion has been reported after intravenous administration of cimetidine in geriatric patients. Ranitidine is more potent and specific and has a longer duration of action than cimetidine. Metoclopramide increases tone in the lower esophageal sphincter and facilitates gastric emptying. However, it does not guarantee a stomach free of gastric contents. Metoclopramide, in conjunction with an H 2 receptor blocker, may be more efficacious than one drug by itself. However, routine use of these drugs in patients without specific risk factors is not currently recommended. Additionally, although nonparticulate antacids work immediately, these intravenous drugs take 30 minutes to several hours for full effect.
Diabetes mellitus with evidence of autonomic dysfunction or gastric atony (gastroparesis), documented symptomatic hiatal hernia, untreated gastroesophageal reflux, pregnancy in active labor, significant obesity, acute abdomen, and current opioid use or abuse are conditions that appear to increase the incidence of gastric regurgitation and aspiration during induction or emergence from general anesthesia or during heavy sedation. Prophylaxis in these situations is recommended. There is no advantage to administration of triple prophylaxis with H 2 -receptor antagonists, soluble antacids, and metoclopramide. If prophylaxis with an H 2 blocker is employed, it should be given the evening before as well as on the morning of surgery. Another effective regimen combines metoclopramide on the morning of surgery and a nonparticulate antacid immediately before surgery.
Despite administration of pharmacologic agents and imposition of fasting, significant amounts of acidic gastric contents may remain. Aspiration of gastric material is a relatively rare occurrence. If a patient is observed to aspirate and if symptoms of coughing, wheezing, or hypoxemia while breathing room air do not develop within 2 hours, significant respiratory sequelae are unlikely. Reliable and otherwise healthy ambulatory patients can probably be discharged after several hours of observation in the postanesthesia care unit (PACU). They must be instructed to contact their physician at the onset of symptoms.
How are patients evaluated before an ambulatory anesthetic?
Ideally, on the day before surgery, the patient would have a private conference with the anesthesiologist who will be caring for him or her. Rapport and trust could be established, a history could be obtained, and physical assessment could be conducted. Appropriate laboratory tests would be ordered, and additional consultations, if necessary, could be requested. Finally, information from old medical records could be obtained.
To avoid an additional trip for the patient and family, some facilities substitute a screening telephone interview for a personal interview conducted by either a nurse or an anesthesiologist several days before surgery. Pertinent medical history can be elicited, general and specific instructions can be given, and reassurance can be offered to the patient. In this scenario, laboratory studies and additional components of the medical record, including an electrocardiogram (ECG) and radiographs, if necessary, are performed immediately before surgery. Previously established criteria and patient comorbidities determine the tests that must be obtained. On the day of surgery, the anesthesiologist must review all information with the patient, conduct the appropriate examination, and obtain informed consent.
The surgeon must assume a large degree of responsibility for the patient’s preoperative preparation. Surgeons are often the only physician to see patients before the day of surgery. Beside conducting a thorough history and physical examination, the surgeon may also request medical consultation when appropriate. To aid in the screening process, surgeons may selectively order laboratory and other examinations according to written guidelines established by the medical facility. However, a mechanism should be in place for free communication between the surgeon’s office and the facility so that appropriate action may be taken when abnormal laboratory values or other reports are received.
The anesthesiologist’s preoperative interview should be conducted in a relaxed, unhurried, and comprehensive manner both chronologically and geographically apart from the operating room. It is less than optimal to conduct a preanesthesia interview and examination with the patient stripped of clothing and strapped to the operating room table. Additionally, with the surgeon and nurses waiting and instrumentation prepared, the pressure on the anesthesiologist to proceed with anesthesia may be intense.
The anesthesiologist should not fail to question patients firmly regarding the use of illicit and nonprescription drugs. In one patient population, 25% of subjects tested positive for commonly abused substances in their urine. Depending on the drug involved, modifications in patient management, including cancellation of surgery, might be well advised. Additionally, users of illicit drugs may have diminished capability or interest in complying with postoperative instructions.
Which preoperative laboratory studies should be obtained before surgery?
For an ambulatory surgery unit that is affiliated with or attached to a hospital, clinical laboratory testing guidelines should be identical to the related institution. It has been well established that “shotgun,” nonselective screening batteries of laboratory, radiographic, and other studies yield an extraordinarily low rate of abnormal findings, few of which may have a significant impact on patient management. Patients scheduled for surgery should have preoperative testing ordered selectively, based on the results of their history and physical examination. Indiscriminate testing can have potentially serious and deleterious consequences. To explain abnormal results, additional studies may be required. Some invasive studies have inherent dangers. Abnormalities often are simply ignored, creating a potential medicolegal liability. Indiscriminate screening often reveals abnormalities that are irrelevant to either the surgery or the choice of anesthetic agent or technique. Some centers use handheld computers to obtain patient histories. Branching lines of questioning dependent on previous answers allow extensive information gathering. At the conclusion of the interactive interview, computers can provide detailed printouts of significant findings and suggest indicated preoperative testing. Many facilities do not require preoperative testing in otherwise healthy men and women <40–50 years old who are undergoing superficial surgical procedures.
Should an internist evaluate each patient before ambulatory surgery?
The same rules and standards regarding preoperative evaluation of patients apply for surgery scheduled on both an inpatient and an ambulatory basis. An internist or medical subspecialist should be consulted whenever the stability of a patient’s medical condition is questionable. Although the magnitude of physiologic perturbations associated with some ambulatory surgery procedures may be minor, there is nothing minor about the administration of an anesthetic. A complete written history and physical examination are required as part of the medical record before administration of anesthesia and commencement of surgery. This history and physical examination may be performed by the surgeon if the patient has no comorbidities that would necessitate input from an internist or medical specialist.
Is an anxiolytic premedication advisable before ambulatory surgery, and what agents are appropriate?
Because the goal of anesthesia for ambulatory surgery is to permit early discharge to home, there was concern that the administration of short-acting anxiolytic or analgesic premedication might delay recovery from anesthesia and prolong time in the PACU with a resultant delay in patient discharge. Many patients experience anxiety in the immediate preoperative period, and pharmacologic management is quite acceptable. The administration of either diazepam, 5–10 mg orally, 1–2 hours before surgery or midazolam, 1–2 mg intravenously, after an intravenous catheter is placed before surgery can ameliorate distress if deemed desirable. The amnestic effect of intravenous midazolam is powerful, and patients may not remember having seen their surgeon if it is administered before meeting the surgeon. Midazolam can also be given orally, although much larger doses (0.5–1 mg/kg) are required because of first-pass hepatic degradation. Opioid premedication may contribute to the incidence of postoperative nausea and vomiting (PONV). Preoperative oral doses of clonidine, a centrally acting α 2 -adrenergic agonist, have been used to provide sedation, reduce anesthetic requirements, and decrease episodes of hypertension and tachycardia during intubation and maintenance of general anesthesia. Side effects include dry mouth, hypotension, and postoperative sedation.
Relaxation techniques can be taught preoperatively to patients and may aid in reduction of anxiety levels. Instruction of these techniques is time-consuming and requires substantial patient motivation. They are usually reserved for select patients with extreme phobias. The effects of longer acting anesthetics and the surgical procedure itself contribute more significantly to the recovery time and delayed discharge. Although time to discharge, a gross measurement, may remain unaffected, tasks that require fine coordination and speedy reaction times may still be deleteriously affected by the anesthetic (i.e., both premedication and intraoperative anesthetic techniques).
What are the reasons for last-minute cancellation or postponement of surgery?
The incidence of last-minute postponement or cancellation of ambulatory procedures often exceeds the cancellation rate for inpatient procedures. Multiple factors contribute to this problem. Repeat physical examination by the surgeon may reveal the disappearance of pathology. Patients may forget and ingest either solid food or liquids before arrival at the medical facility. Abnormal test results that were not available or not previously reviewed may be discovered. Communication between the surgeon and anesthesiologist regarding laboratory abnormalities helps to reduce the incidence of last-minute cancellation of surgery, consequences of which distress both the patient and the surgeon and make for inefficient use of available operating room time. Additional questioning may reveal either new symptoms or significant history that was not previously elicited. Physical findings apparent on a last-minute assessment by the anesthesiologist may preclude the safe administration of an anesthetic. Examples include an acute upper respiratory tract infection or an exacerbation of bronchospastic pulmonary disease. Finally, patients may arrive late to the facility or without a responsible escort to accompany them home.
What is the ideal anesthetic for an ambulatory surgical procedure?
No single anesthetic is ideal for every procedure. However, the goal of the anesthetic is to allow for patient discharge shortly after completion of the procedure. An ideal general anesthetic agent would have rapid onset, permit quick return to baseline levels of lucidity and equilibrium, and provide freedom from deleterious cardiovascular and respiratory effects. It would provide intraoperative amnesia, analgesia, and muscle relaxation and possess antiemetic properties. This ideal single agent does not exist at the present time ( Table 73-1 ). In an attempt to avoid some of the unpleasant side effects associated with general anesthesia, regional anesthetic techniques, including field blocks, intravenous regional block (i.e., Bier block), various approaches to the brachial plexus, ankle block, and spinal and epidural anesthesia, have been offered to patients as an alternative to general anesthesia.
|Drug||Class||Action||Intravenous Dose Range||Potential Side Effects|
|Midazolam||Benzodiazepine||Sedative-hypnotic||1–4 mg/70 kg||Apnea and potentiation of hypotension in combination with opioids|
|Propofol||Diisopropylphenol||Induction sedative-hypnotic||2.0–2.5 mg/kg; 0.1–0.2 mg/kg/minute infusion and 10–20 mg bolus as needed||Pain on injection; hypotension; respiratory depression; apnea|
|Fentanyl||Opioid||Analgesia||1–3 μg/kg||Respiratory depression; apnea; nausea; vomiting; miosis; depression of cough; bradycardia; hypotension|
|Remifentanil||Opioid||Analgesia||Bolus 0.5-1 μg/kg, then infusion 0.02–0.3 μg/kg/minute||Respiratory depression; apnea; nausea; vomiting; miosis; depression of cough; bradycardia; hypotension|
|Ranitidine||H 2 blocker||Histamine receptor antagonist||150 mg orally or 50 mg IV preoperatively||Headache; fatigue; drowsiness; dizziness; nausea; vomiting; abdominal pain; diarrhea; constipation|
|Naloxone||Opioid antagonist||Competitive antagonist||20–40 μg bolus, titrate to effect||Precipitate withdrawal symptoms; hypertension; tachycardia; arrhythmias|
|Flumazenil||Imidazobenzodiazepine||Specific benzodiazepine antagonist||0.2 mg every 1 minute up to total dose of 1.0 mg; may repeat every 20 minutes||Central nervous system excitation; seizures; nausea; vomiting; acute withdrawal|
|Droperidol||Butyrophenone||Antiemetic||10–20 μg/kg; 0.625–1.25 mg/70 kg||Dysphoria; extrapyramidal signs; sedation; hypotension; la belle indifférence; catatonia; prolonged QT interval; torsades de pointes, FDA “black box” warning|
|Ondansetron||5-HT 3 receptor||Antiemetic||4 mg/70 kg over 2.5 minutes||Pain on injection; rash; headache|
|Dexamethasone||Steroid||Antiemetic, antiinflammatory||4–10 mg||Perineal “burning”; hyperglycemia|
|Transderm scopolamine||Anticholinergic||Antiemetic, anti–motion sickness||1.5 mg slow-release patch||Dry mouth; dysphoria; sedation|
|Labetalol||alpha 1- and beta-adrenergic blocker||Antihypertensive||5–20 mg increments every 5 minutes up to total dose of 80 mg||Bronchospasm; conduction delays; bradycardia|
|Esmolol||Relative beta-1-selective adrenergic blocker||Antihypertensive, antiarrhythmic||10-mg bolus; add increasing doses every 3 minutes as needed up to 300 mg total; then may administer 50–200 μg/kg/minute||Bradycardia; conduction delays; hypotension; bronchospasm; congestive heart failure|
|Desflurane||Ether||General anesthesia||Minimum alveolar concentration 6% inhaled||Myocardial depression; respiratory depression; airway irritation|