Ambulatory (Outpatient) Anesthesia

Definitions

Although ambulatory surgery is widely practiced, the precise definition can vary across countries and healthcare systems. For consistency, we have used the definition proposed by the cofounder of the IAAS: “A surgical day case is a patient who is admitted for investigation or operation on a planned non-resident basis and who none the less requires facilities for recovery. The procedure should not require an overnight stay in a hospital bed.” This definition requires the patient to be managed with the intention of same-day discharge from the outset, in addition to admission, operation, and discharge all occurring on the same calendar day. Including management intention in the definition ensures no incentive is provided to discharge a planned inpatient at short notice, who would be without all of the preparation and support required for optimal postoperative care.

Short-stay surgery embraces all of the principles of ambulatory surgery and includes a postoperative overnight hospital stay. Extended observation may be prudent for certain patients with significant comorbidities, lack of social support, or for those who have undergone a procedure that is either too extensive or performed too late in the day to be compatible with same-day discharge. We have included short-stay surgery in this chapter because the objectives of minimizing physiologic disturbance to improve the quality of recovery and reduce the length of stay are the same as those of ambulatory surgery and much of the perioperative management is similar.

Hospital Integrated

The simplest model of ambulatory surgery is one with shared inpatient surgical facilities, but with separate areas for preoperative preparation and recovery of ambulatory patients. This model of care is most often inefficient and brings the risk for ambulatory procedures being delayed or even canceled in favor of urgent or emergent inpatient procedures. However, by dedicating certain operating sessions to ambulatory surgery and using strict protocols, efficiency in one such unit has been described as almost equal to that of a self-contained unit. The design is flexible, allowing the proportions of ambulatory and inpatient surgery to vary from day to day, and, as new procedures are transferred to ambulatory surgery, it does not require duplication of equipment and skills in a separate facility.

Hospital Self-Contained

These self-contained units are functionally and structurally separate from inpatient facilities with their own reception, admission areas, operating rooms, recovery areas, and administrative facilities. This design promotes a patient-focused flow of care. It ensures functional separation from urgent and emergency work while maintaining the accessibility of resources available in the main hospital. In many ways it is an ideal model of care. However, the local capacity for ambulatory surgery may be reached, and duplication of operating room equipment and skills may then occur for those procedures still commonly performed on both an ambulatory and inpatient basis.

Freestanding

Freestanding ambulatory surgery centers ensure complete separation of perioperative care from inpatient and emergency work. This improves efficiency and allows complete focus on a workflow designed for ambulatory care. While rare perioperative complications may occur that require elevation of care or additional resources, appropriate patient selection and preparation minimize this risk. Some freestanding units have the capacity for overnight stays to provide additional nurse-monitored recovery. However, all freestanding units must have a detailed plan for the care of patients who need urgent or emergent transfer to a nearby hospital. Ambulatory surgery centers vary from highly specialized, single-surgery facilities performing ambulatory total joint replacements or bariatric procedures to those that can accommodate multiple specialties and support a variety of service lines.

Office-Based

Performing ambulatory surgery, diagnostic procedures, or both in a facility associated with a physician’s office is a rapidly expanding model of care within the United States. The main advantages are increased convenience for the patient and surgeon, and lower total procedure costs. Office-based services and facilities have historically been subject to less regulatory requirements when compared to those imposed on ambulatory surgery centers. Furthermore, they may have more significant limitations with respect to equipment, personnel, and environment along with reduced capability when managing perioperative complications. These limitations, however, are rapidly changing. In the United States, physician offices that provide services that include procedures involving moderate to deep sedation or general anesthesia may be subject to state regulatory requirements for accreditation and adherence to standards with respect to governance, facility environment of care, availability of equipment, credentialing of staff, and continued medical education for personnel. A more detailed discussion of office-based anesthesia can be found later in the chapter.

Surgical Factors

The development of minimally invasive surgery, improvements in surgical technique and pain control, and the availability of shorter-acting anesthetics have dramatically increased the range of surgical procedures compatible with same-day discharge. While the duration of surgery has traditionally been a determinant of outcome, the extent of surgical trauma now appears to be the more significant determinant. There should be no expectation of significant blood loss, large perioperative fluid shifts, or the need for complex or specialized postoperative care. Surgical complications remain the single greatest cause of unanticipated hospital admission. In the United States and the United Kingdom, an overnight stay for patients who have undergone an ambulatory surgery procedure in any venue receives no additional payment, so the extra costs are borne by the facility. The British Association of Day Surgery publishes a directory of over 200 different surgical procedures and suggests aspirational targets for the proportions of each that are suitable for either ambulatory or short-stay surgery. A selection of these are shown in Table 72.1 .

Laparoscopic cholecystectomy is now a routine ambulatory surgical procedure in many countries, and increasingly same-day discharge is seen as safe and beneficial after a variety of advanced laparoscopic procedures, including fundoplication, hysterectomy, nephrectomy, pyeloplasty, radical prostatectomy, and gastric banding. Minimally invasive approaches have also facilitated same-day discharge following unicompartmental knee and hip arthroplasty. One series of 2000 patients undergoing laparoscopic Roux-en-Y gastric bypass for morbid obesity reported 84% being discharged within 23 hours with a readmission rate of less than 2%.

Even specialties like neurosurgery, traditionally associated with complex inpatient care, have begun to embrace day surgery. Same-day discharge of selected patients undergoing awake craniotomy for supratentorial tumors was first described in 2001. More recently, some patients requiring general anesthesia for tumor resection and even aneurysm clipping have been discharged on the day of surgery. Increasingly, a number of non-elective procedures, such as abscesses, incarcerated hernia repairs, and appendectomies, are being managed through day surgery pathways. In parallel, several less invasive procedures, such as diagnostic or therapeutic hysteroscopy, are moving from ambulatory surgery into the procedure room, outpatient clinic, or office.

While postoperative pain control in the home environment may present substantial challenges, perhaps the greatest barrier to the development of ambulatory surgery is conservatism, based on incorrect perceptions and concern about serious complications that might occur following discharge. For example, despite convincing data that most primary hemorrhages are evident within 6 to 8 hours of tonsillectomy, an overnight stay is still routine in some countries while others discharge 80% of patients or more on the day of surgery. Similarly, ambulatory thyroid surgery was first shown to be safe and effective in 1986, yet its widespread adoption has been slow, predominantly because of concerns about bleeding and airway compromise. Such complications are rare, especially when surgery is undertaken by specialists who perform a high volume of cases with assiduous hemostasis, allowing short times to discharge to be achieved. Performing thyroidectomy under local anesthesia also appears to increase ambulatory surgery rates, perhaps because of the careful surgical technique required. In the case of breast surgery, concerns about postoperative psychological support has delayed transfer of mastectomy and other cancer operations into ambulatory care in the United Kingdom, although it is now recognized that early discharge improves the psychological well-being of these patients by minimizing the time away from home. Challenging conventional wisdom also may be beneficial; for example, discontinuing the routine use of drains after mastectomy or axillary node clearance does not increase morbidity, including from wound seroma, while facilitating same-day discharge. Day surgery management of breast cancer is associated with fewer complications than inpatient care.

Medical Factors

In the past, ambulatory surgery has relied on relatively rigid patient selection criteria in the attempt to limit the occurrence of postoperative complications. In practice, however, most of these criteria predict the occurrence of treatable perioperative adverse events, but not the need for unanticipated admission or readmission. Although an index combining age, length of surgery, and preexisting conditions, such as peripheral or cerebrovascular disease, can identify a group at higher risk for hospital admission, the specificity is poor and same-day discharge is still the most likely outcome. Ambulatory surgery is very safe, with a perioperative mortality less than 1 in 11,000, better than that in the general population. More recent studies have confirmed the continuing safety of ambulatory surgery, despite increasing surgical and patient complexity.

Relatively few absolute contraindications now exist to ambulatory surgery. Patient suitability should be assessed on the basis of overall health, taking into account both the risks and benefits of early discharge, and certainly not determined by arbitrary limits, such as age, body mass index (BMI), or ASA physical status. Chronic conditions should be relatively stable and must be optimally treated before any elective procedure, irrespective of the planned postoperative management. Many stable chronic diseases, such as diabetes, asthma, or epilepsy, are often better managed by the patients than by the perioperative team, and ambulatory surgery facilitates this by easing the disruption to their daily routine. A distinction should be made between preexisting conditions that make a patient more difficult to manage on the day of surgery and those that increase the occurrence of late postoperative problems, which are a relative contraindication to ambulatory surgery.

A good example is obesity, which is associated with numerous perioperative problems for the surgeon, anesthesiologist, and operating room personnel (see also Chapter 58 ). Safe care of the obese patient may require the availability of experienced staff and specialized equipment, such as longer instruments and wider operating trolleys but any risks are resolved soon after immediate recovery and are not prevented by postoperative overnight hospitalization. Obese patients benefit from ambulatory management with early mobilization, the use of short-acting drugs, and avoidance of opioid analgesia. Obesity does not increase the rate of unanticipated admission, postoperative complications, readmission, or other unplanned contact with health professionals following discharge. Even morbid obesity (BMI > 40 kg/m ² ) and super obesity (BMI > 50 kg/m ² ) are no longer considered absolute contraindications to same-day discharge. Obesity increases the likelihood of further comorbidities, but these should be evaluated individually.

Social Factors

In general, if a patient’s living arrangements were adequate before surgery, they should also be suitable after surgery. Some adaptations may be necessary if the patient’s mobility is severely compromised by their procedure—for example, by the use of casts. Access to a telephone to summon assistance is a minimum requirement, but is rarely problematic with the ubiquitous availability of mobile telephones. Patients usually live within a reasonable traveling distance of the surgical unit, but this may be impractical in rural or sparsely populated areas. Journeys of hundreds or thousands of miles are not unheard of in parts of Scandinavia after ambulatory surgery. For patients who live far away, consideration should be given to the provision of emergency care close to home and for the comfort of the patient during the journey. Patients who choose to travel long distances after ambulatory surgery usually are very satisfied with their care. Hospital hotels, which provide nearby accommodation but little or no nursing care, are a higher-cost alternative for the patient and have largely been abandoned as an impractical option.

A universal safety feature is to require all patients having surgery under general anesthesia or sedation to be discharged with a responsible adult escort and the recommendation to have someone stay with them for the next 24 hours. If the 24-hour companion is mandated, patients often disregard postoperative instructions and send their escorts away if they feel well at home. In the United States, it is standard practice to require that patients who have received other than unsupplemented local anesthesia be discharged with a responsible adult ; if not, surgery is postponed. A Canadian single-institution study reported discharging patients alone when their escort fails to arrive, yet this practice did not appear to increase emergency room visits or readmission rates within 30 days. The Association of Anaesthetists of Great Britain and Ireland has suggested that an escort may be required in most (but not all) cases, with exceptions when the surgery is relatively minor and anesthesia brief so the patient is not compromised by the sedative effects of anesthesia or analgesia by the time of discharge. If patients are discharged alone, they should not drive themselves home ; several serious accidents have occurred, especially after the use of sedative doses of benzodiazepines.

The Role of Preoperative Assessment

An effective preoperative assessment process is essential for the delivery of safe, high-quality, and efficient ambulatory surgery. Rather than trying to select specific, low-risk groups of patients, ambulatory surgery is increasingly seen as the default option for a wide range of surgical procedures, with inpatient care chosen only for those with insurmountable barriers to early discharge. Other than identifying this small group of patients, preoperative assessment is primarily required to evaluate and optimize patients and to provide appropriate information ( Table 72.2 ). These assessment and optimization functions can be further distilled into two key questions: “Is there any benefit to this patient of being in hospital overnight after surgery?” and “Is there anything that needs to be done to enable this patient to be a day case?”

Mechanisms and Timing of Preoperative Assessment

The timing of preoperative assessment is crucial, because it must be done early enough in the pathway to allow for any necessary investigations and optimization without delaying the planned procedure. This becomes increasingly difficult as the interval between the decision to operate and the date of surgery becomes shorter. Ideally, preoperative assessment should immediately follow the decision to operate, by providing a “one-stop shop.” This type of service, in which preoperative assessment immediately follows the surgical consultation, is highly valued by patients, although it can be difficult to manage because of variations in the demand for the service. An alternative is to use a basic screening tool to identify those patients who can proceed directly to surgery and those who require further investigation or management ( Fig. 72.1 ).

A case can be made for all patients to be seen in a preoperative assessment clinic; however, in practice this places a major demand on resources and is also inconvenient for patients who may need to take additional time off work. Screening allows many patients to undergo assessment by telephone or questionnaire, with clinic attendance required only if unexpected problems are uncovered or if requested by the patient. When telephone assessment was chosen for all young healthy patients scheduled for minor breast surgery, only 2% of patients had problems identified that required further assessment in the ambulatory surgery center. By using a computerized information-gathering and triage tool, combined with some basic information about the planned procedure, approximately onethird of ambulatory patients did not need to see an anesthesiologist before the day of surgery. This approach eliminates the need for a face-to-face assessment before the day of surgery but does not eliminate an evaluation of the patient’s medical information in advance of surgery. In contrast, advance face-to-face preoperative assessment is more advisable for older patients, in whom multiple comorbidities, polypharmacy, and social problems are all more likely. Early discharge planning is also important for older patients, to address environmental issues that can be improved to support recovery.

In the United Kingdom, preoperative assessment is usually performed by nurses working closely to protocols and supported by anesthesiologists who provide advice and personally assess the more complex patients. In the United States, anesthesiologist-led, protocol-driven preoperative assessment is often used for healthy patients having minor procedures. However, these preoperative evaluation clinics are frequently used in US hospitals, not just for ambulatory patients with more complex medical or surgical issues but also for the majority of inpatient surgery cases that are admitted on the morning of surgery. More complex patients have their anesthesia preassessment performed by an anesthesiologist. A comprehensive preoperative history and physical evaluation by a physician extender is often also provided in the preoperative assessment clinic for the surgeon. Using a physician extender to assist in preoperative evaluation maintains patient safety and satisfaction, promotes flexibility with scheduling of providers, and increases staff satisfaction. Appropriately trained nurses were just as effective as trainee medical staff in detecting information likely to influence subsequent patient management, but they ordered significantly fewer unnecessary tests.

Patients generally rate their preoperative assessment clinic experience very favorably, with their greatest concerns relating to waiting times. Scheduling appointments of approximately twice as long for patients of ASA physical status grades III and IV than for those of grades I and II has been shown to reduce backlogs and maximum waiting times for preoperative evaluation to an acceptable level of about 10 minutes.

Preoperative Investigation

The history and physical examination remain key elements of preoperative risk assessment, despite the availability of more sophisticated technologies. In fact, most useful information can be obtained from the history, supplemented by simple observation of the patient. Basic physical examination, such as routine chest auscultation, is often considered unhelpful in adult ambulatory surgery patients, because findings that are unaccompanied by symptoms or functional limitation do not alter management. Although aortic stenosis may remain asymptomatic until it is quite severe, chest auscultation may be unreliable in its detection. In one high-risk population, 31% of patients without a detectable murmur nevertheless had some degree of aortic stenosis that was moderate or severe in 10% of cases, whereas 31% of patients with a suggestive murmur did not have aortic stenosis on echocardiography. Ten patients with severe aortic stenosis (valve area 1 cm ² or less, gradient 35-58 mm Hg) tolerated an unmodified anesthesia regimen for electroconvulsive therapy on 144 occasions without problems, suggesting that ambulatory surgical patients with undiagnosed aortic stenosis may not inevitably be at excessive risk, when combined with appropriate procedure selection.

It is recognized that routine laboratory investigations are unhelpful because they may generate false-positive results or do not alter subsequent management. In addition, such tests increase costs, are unpleasant and time-consuming for patients, and may lead to repeat testing with even further expense and delays. Consequently, many authorities recommend selective testing, based on indications from the patient’s clinical evaluation and demographics.

Although comorbidities become more prevalent with age, additional preoperative testing for older patients may still be unnecessary. In patients 70 years of age or older, routine preoperative blood test results were not predictive of postoperative complications. While preoperative electrocardiograms of patients over 50 years of age detected abnormalities, such as bundle branch blocks, predictive of postoperative myocardial infarction, the recordings did not provide additional predictive value to that obtained from the patient history. The National Institute for Health and Care Excellence no longer advocates patient age be used as a criteria for routine preoperative testing and also recommends few, if any, tests for healthy patients undergoing minor or intermediate surgery. One large pilot study demonstrated that the elimination of all preoperative testing resulted in no increase in adverse events in the perioperative period and did not alter the rate of unanticipated admission or readmission within 30 days compared to indicated testing.

Provision of Information

Patients need to be informed about what will happen on the day of surgery, because a well-prepared patient is likely to be more relaxed and more satisfied with the service provided. A well-informed patient is also more likely to comply with important instructions and protocols, such as fasting intervals and management of regular medications. Many patients are disproportionately worried about highly unlikely outcomes, such as death and awareness, yet somewhat less concerned about more common consequences such as nausea, vomiting, and postoperative discomfort. The preoperative discussion should help to allay the anxiety associated with unlikely risks. It was found that a specially designed website with text, animation, and video significantly increased patients’ knowledge about anesthesia when compared with a combination of verbal and written information.

Patients should be given specific information, preferably supplemented in writing, about how to manage their usual medications in the preoperative period. Some drugs (e.g., warfarin) should be stopped several days before surgery and some hypoglycemic agents omitted before surgery. However, other important medications should not be omitted. ^{, ,}

Information about medications should include over-the-counter and herbal products, which are commonly used but often regarded by patients as harmless and safe. Despite some serious consequences and interactions associated with herbal medications, not all practices specifically ask and advise patients about these products on a routine basis. (see also Chapter 33 ).

Preoperative Fasting

Almost universal agreement now exists that the safe fasting interval for clear liquids is no more than 2 hours, in contrast to 6 hours for light meals. These fasting intervals result in safe gastric volumes even in obese adults, children, and patients with diabetes and gastrointestinal (GI) reflux. Indeed, a 2-hour interval is probably conservative, given that the stomach empties clear fluids exponentially, with a half-time of approximately 10 minutes.

Despite guidelines based on decades of research, implementation remains poor, with many patients fasting for excessive periods and experiencing significant discomfort. Rather than focusing on a minimum fasting time, patients should be encouraged to keep drinking until the latest time necessary for safety to reduce preoperative dehydration and its associated consequences. In practice, this may mean asking patients to have a drink just before they leave home or even providing a drink on arrival if surgery is still more than 2 hours away. Advising patients to drink on the morning of surgery also makes it easier for them to take their medications. Milk added to tea or coffee does not appear to delay gastric emptying and, in the United Kingdom, may provide more palatable choices of preoperative beverage. The US practice is for clear fluids only. Recently, it has been shown that allowing patients unrestricted access to water right up until they were called to the operating room significantly reduced the incidence of postoperative nausea and vomiting (PONV) without increasing the occurrence of clinically-significant pulmonary aspiration. Practices such as chewing gum before surgery also may not be harmful. No consistent evidence exists of a clinically important increase in gastric volume associated with gum chewing in adults, while in children it may promote gastric emptying and could also serve as a useful route for premedication.

Besides feelings of thirst and hunger, excessive fasting also results in hypoglycemia in significant numbers of patients, with 14% of fasted healthy female ambulatory surgical patients having an admission blood glucose value of 45 mg/dL (2.5 mmol/L) or less. Preoperative oral carbohydrates have been shown to improve subjective well-being, reduce thirst and hunger, and reduce postoperative insulin resistance, although convincing evidence of reduced length of stay is lacking, at least for shorter procedures.

Premedication

Premedication traditionally refers to the administration of medications to relieve anxiety before surgery. However, the term encompasses any medication given in the preoperative period and therefore includes prophylactic analgesia and antiemesis agents, as well as drugs used to promote gastric emptying or counteract acid secretions.