According to the International Association for Ambulatory Surgery (IAAS), ambulatory surgery should be defined as ‘an operation/procedure, excluding an office or outpatient operation/procedure, where the patient is discharged on the same working day.’ The origins of ambulatory surgery can be traced back to the pioneering work of James Nicholl at the Glasgow Royal Hospital who reported 8988 paediatric day‐ case procedures between 1899 and 1908. Despite initial scepticism from the surgical profession, there has been a rapid expansion in the complexity and amount of ambulatory surgery in recent years: between 1989 and 2003 the percentage of elective surgery undertaken as day case in the UK increased from 15 to 70%. Many health services have set targets for the percentage of elective surgeries to be done as day‐case procedures, and in the UK this target is set at 75%.

The rise of ambulatory surgery has been driven by technological advances that reduce the need for overnight hospital stays, enhanced recovery programmes that advocate early mobilisation, and the need for economic efficiency. With growing interest in ambulatory surgery, multiple associations have been formed promoting education, quality standards, and research in the field.

Infrastructure

Ambulatory care is delivered in various environments, including

• Free‐standing self‐contained units
  
• Integrated self‐contained units
  
• Integrated non‐self‐contained units

Free‐standing units, separate to inpatient units, are common in the United States, increasing in number from 67 in 1976 to over 4000 in 2004 (IAAS: day surgery). They may be multidisciplinary, serving a larger market, or uni‐disciplinary. Potential benefits include cost‐effectiveness and efficiency because it is easier to generate a streamlined care pathway and to encourage teamwork amongst healthcare professionals. Furthermore, they may have lower rates of hospital‐acquired infection. The disadvantage is that they are remote from a comprehensive medical facility with a full range of specialties including intensive care, meaning that there will occasionally be a need for outsourcing and transfer of patients. The need for low‐risk patients ultimately encourages stricter patient selection, self‐limiting the service. Most unplanned overnight admissions after ambulatory surgery are due to bleeding and longer‐than‐expected procedure length, with urological and gynaecological surgery accounting for a particularly high proportion of bleeding patients (Vaghadia 1998).

Integrated self‐contained ambulatory units are located on a hospital site with their own dedicated theatres and personnel. They are generally seen as the ideal model for ambulatory surgery, benefiting from the comprehensive range of medical services provided by that hospital, whilst also specialising in providing a streamlined ambulatory service with one dedicated team well trained in ambulatory surgical care.

Integrated non‐self‐contained ambulatory units vary significantly in set‐up: some may not have dedicated theatres or personnel. This makes the system inefficient, because there is a chance that low‐risk day‐case procedures may be cancelled, a streamlined patient pathway is often lacking, and unintended overnight stays arise due to difficulties ensuring safe discharge. However, if there is a dedicated ambulatory ward and theatres, this environment does have some benefits; it is easily expandable, meaning that as new procedures are transferred to day surgery, the same infrastructure can be used with appropriate retraining of staff.

Pre‐operative Assessment

Once the decision to operate has been established and the intended procedure is planned as a day case, a dedicated pre‐assessment team, generally made up of trained nurses, should comprehensively assess the patient. This assessment should ideally take place in the same unit in which the procedure will take place but can be undertaken remotely via telephone or computer. It should happen far enough in advance so that patients’ co‐morbidities, medications, and social factors can be optimised preoperatively.

The pre‐operative assessment begins with gathering information about health, medications, and social circumstance. The health assessment is generally history‐based and most commonly involves a questionnaire with basic screening questions and more detailed history where appropriate. Pre‐operative examination and investigations including blood tests, ECG, and X‐rays are less useful in most patients. A decision is then made regarding whether the patient is suitable for day surgery. Modern ambulatory units have moved away from a specific set of contraindications and instead assess patient suitability individually according to the combination of physiological status, social circumstance and intended procedure.

Social Selection Criteria

Several social factors must be considered before ambulatory surgery. Patients or carers must be able to understand the nature of the procedure, and be willing to adhere to the peri‐operative instructions. Patients must have appropriate support at home; in general, they need to be discharged into the care of a responsible adult for 24 hours after the operation, although this is probably excessive for some minor operations. Additionally, a generally accepted rule is that they must live within one hour’s travel time to the surgical unit. In those living remote from ambulatory unit, the option of an overnight local lodging can be discussed, instead of overnight hospital admission.

Physical Selection Criteria

There are multiple factors that reduce the suitability of patients for day surgery and must be assessed in detail prior to surgery (Fong 2014). Identifying high‐risk patients can help facilitate a multidisciplinary strategy to optimise their pre‐operative condition, anticipate intraoperative challenges, and plan postoperative disposition (Walsh 2018). Although a comprehensive review of these is beyond the scope of this chapter, we will mention a few notable parameters.

Age should not independently decide whether a patient is suitable. In one study, elderly patients did not have worse outcomes than younger patients (Chung 1999), although in another, advanced age was associated with greater rates of readmission (Whippey 2013). Ambulatory surgery may actually confer some benefits to the elderly population, having been shown to reduce rates of post‐operative cognitive dysfunction (Rasmussen 2015).

The American Society of Anaesthesiologists grading system (ASA grade) is used to evaluate a patient’s physical state before surgery and classifies patients into 6 categories. Grade 1 being a normal healthy patient and grade 5 being moribund patient. The ASA grade is not a particularly useful measure of suitability for day surgery. An ASA 3 patient does not experience greater complication rates when compared to an ASA 1 or 2 in the medium to late post‐operative period (Ansell 2004). Some ASA 4 patients may also be suitable for procedures undertaken using local or regional anaesthesia.

Suitability of obese patients is a controversial area, a body mass index (BMI) of up to 40 being acceptable for the majority of procedures and many anaesthetists would accept higher BMIs (Atkins 2002). Complication rates do appear to be higher in the extremely obese group (BMI > 50 kg/m²), although readmission rates are not significantly greater (Joshi 2013).

With regards to chronic medical conditions, a general rule is that stable patients are fit for ambulatory surgery. Chronic obstructive pulmonary disease (COPD) is not a contraindication for ambulatory surgery. Asymptomatic patients have a low risk of post‐operative complications, but those who have been symptomatic within a month of the proposed surgery may need to have their procedure postponed (Warner 1996). Smokers should be encouraged to stop smoking, as even short‐term cessation pre‐operatively has been demonstrated to reduce complications (Myles 2002). Patients with obstructive sleep apnoea should have good control of symptoms and be established on nasal continuous positive airway pressure pre‐operatively and during the post‐operative period.

Cardiovascular status should also be assessed pre‐operatively. Patients with hypertension should have their blood pressure reasonably controlled. The majority of those with ischaemic heart disease will be suitable, except for those with unstable or severe angina and those who have experienced recent myocardial infarction. Additionally, ambulatory surgery is generally not undertaken within a year of drug‐eluting stent placement (Wijeysundera 2012). Diabetes mellitus does not itself preclude a patient from day surgery; in fact, day surgery reduces disruption to normal routine. However, patients should ideally be screened for other co‐morbidities including cardiovascular and renal dysfunction. Patients with end‐stage renal failure may be appropriate for minor ambulatory procedures undertaken under local or regional anaesthesia but, given their poor physiological state and the practical issues with regards to dialysis, major ambulatory operations are generally contraindicated.

Preparation for Surgery

Once the patient has been adequately assessed and deemed suitable for ambulatory surgery, the clinical team will start to prepare. This will involve completion of any further anaesthetic investigations and surgical diagnostics. Consent should be obtained with explanation and post‐operative plan discussed.

The patient must be given appropriate information regarding the perioperative period. This will include an overview of fasting requirements, medications that need to be taken, and information pertaining to personal hygiene. In addition, simple information about location and timings should be provided. Finally, the patient and carer/responsible adult should be given information on whom to contact for queries or help with post‐operative complications.