9

Strategies for outpatient anaesthesia

Anil Gupta* MD, FRCA, PhD

Department of Anaesthesiology and Intensive Care, University Hospital, SE-701 85 Orebro, Sweden

With the expansion of ambulatory surgery in the Western world over the last 10 years, it hasbecome increasingly important to identify patients at risk of perioperative complications and touse appropriate methods to decrease these risks. The confidential enquiry into perioperativedeaths was one of the first national programmes instituted to identify patients at risk after theoperation. Although the focus for this initial enquiry was on perioperative mortality, recentdevelopments have increasingly focused on identification of perioperative morbid events. Thefirst large prospective study on outpatients found a very low incidence of death after ambulatorysurgery, but with the acceptance of high-risk patients for ambulatory surgery in recent years it islikely that perioperative morbidity will increase in the future. Therefore, identification of thepatient at risk is important in order to apply known strategies to decrease these risks. We firstneed to know what tools are available to detect these ‘at-risk’ patients. Unfortunately, many ofthe tools used are very subjective and lack both sensitivity and specificity. In this chapter, anattempt has been made to outline the risks related to surgery, anaesthesia, the patient and theprocedure, and finally the role of the establishment. Later, strategies are discussed which couldreduce the perioperative general and cardiorespiratory risks in the ambulatory surgical patient.Many of these strategies are derived from the inpatient since appropriate data in outpatients arelacking. Future studies should thus focus on data derived from outpatients and prospective,randomized, double-blind studies in a large population of patients in order to first identify thepatient at risk and subsequently to use drugs and techniques that reduce these perioperativerisks.

Key words: surgery; ambulatory surgery; risks; mortality; morbidity.

Perioperative deaths have occurred since time immemorial, but documentation ofthese has not been equally rigid. Specifically, the denominator (the number of patientsoperated on) has been a source of some uncertainty in the past, which is why theincidence of complications and perioperative deaths has been unclear. With theavailability of computers in medical practice in the 1980s many databases are nowavailable, and through a system of quality control, registration and documentation ofdeaths and complications, it has become increasingly common to have access to reliableinformation. This has not only led to a system of benchmarking but also to the evolution

1521-6896/$ - see front matter Q 2004 Elsevier Ltd. All rights reserved.

Best Practice & Research Clinical AnaesthesiologyVol. 18, No. 4, pp. 675–692, 2004

doi:10.1016/j.bpa.2004.05.005available online at http://www.sciencedirect.com

* Corresponding author. Tel.: þ46-19-127-479; Fax: þ46-19-602-100.E-mail address: anil.gupta@orebroll.se (A. Gupta).

of tools by which quality of care can be compared using both major and minorendpoints. Recent studies have therefore increasingly focused on outcome as a majorfactor when comparing different anaesthetic and surgical techniques.

Uniform agreement on what constitutes ‘perioperative’ deaths has not beenreached, and so one commonly considers 7- or 30-day mortality. In the case ofoutpatient surgery, there is even more uncertainty about the definition and thereforeterms such as ‘in-hospital’ and ‘out-of-hospital’ mortality have been defined in differentstudies.

One of the first large studies implemented into perioperative deaths was throughthe active initiative taken by British doctors, and the first report on the confidentialenquiry into perioperative deaths (CEPOD) was published in June 1990. Since then, atotal of 14 reports have been published, and the last six reports are available on-line(http://www.ncepod.org.uk/index.htm) and can be downloaded in their entirety. Theaim of the organization (which is now under the aegis of the National Institute forClinical Excellence, NICE) is to review clinical practice and identify potentiallyremediable factors in the practice of anaesthesia, surgery and other invasive medicalprocedures. The aim is also to look at the quality of the delivery of care and notspecifically the causation of death. Unfortunately, similar reports are not available in theUSA because of a more complicated medical insurance system. However, data fromMediclaim and other similar organizations has provided major input into perioperativedeaths.

It is strongly believed in the medical and patient communities that ambulatorysurgery involves healthy outpatients having simple and minor surgery. This is obviouslynot true, as evidenced by the increasing numbers of ASA III and IV patients, and theever-increasing pressures from a variety of sources to do more complex procedures onan ambulatory basis.1

HOW DO WE ASSESS PERIOPERATIVE RISKS?

In order to reduce perioperative risks, we must be able to use tools to measure it.Mortality is a definite but crude endpoint for the assessment of perioperative risk,specifically in the outpatient setting. Therefore, morbidity is often considered theendpoint of interest, and numerous indicators of morbidity have been discussed andmethods to assess these developed. Amongst the endpoints commonly used tomeasure morbidity following anaesthesia in ambulatory surgery are length of hospitalstay (home-readiness), time to transfer to a step-down unit, time to awakening, and theincidence of various minor complications (pain, nausea and vomiting, tiredness,headache, etc.) in the post-anaesthesia care unit as well as after discharge home. Manyof these endpoints are surrogate measures and do not assess a parameter ofconsequence to the patient (transfer to step-down unit) or the caregiver (time toawakening). Others are indirect measures of well-being following anaesthesia and donot measure a direct morbid event (length of hospital stay). Some of the parametersmeasured do not have a clear and objective method of measurement, which makes itdifficult to define the potential risk to the patient (tiredness, headache). One parameterthat has been extensively studied and has well-defined measurement methods is post-operative nausea and vomiting (PONV). Not only are there scales available to predictthe risk of PONV, but some of these scales have been shown to be consistent inpredicting, and thereby preventing, PONV. One example of a scale that has been usedand studied is the Apfel score.2 When using this score, one is able to provide

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a predictive risk for the patient, and steps can then be taken to reduce this risk.Similarly, the post-anaesthesia discharge scoring system (PADSS), and its subsequentmodification, is a standardized system for measuring discharge from the hospital.3 Thistoo has predictive potential in that it is possible, when using this scale, to predict theeffect of drugs and anaesthetics on discharge times. The PADSS can only be used toguide the physician in predicting which drugs and techniques are associated withshorter convalescence times, which is not a direct measure of perioperative risk.

Mortality following regional anaesthesia during ambulatory surgery is extremelyrare, but major morbidity, although also uncommon, can sometimes be devastatingto the patient.4 Minor complications in the form of headache, urine retention andpartial hearing loss after spinal anaesthesia, reversible nerve injuries followingperipheral nerve blocks, as well as hemidiaphragmatic paralysis, Horner’s syndromeand intravascular injections following interscalene block, are well known. Theseconstitute important (though rare) perioperative risk factors following regionalanaesthesia.

WHATARE THE KNOWN PERIOPERATIVE RISKS FOR OUT-PATIENTS?

As the specialty of ambulatory surgery focuses on its role in the 21st century, it isimportant to acknowledge the patient’s perspective and desire to undergo life-prolonging or quality-of-life-improving procedures. The ability of the anaesthesiologistto impact on the decision process and overall risk is a challenge. It is imperative torealize that ‘perioperative’ risk is multi-factorial and depends upon the interaction ofanaesthesia-, patient- and surgery-specific factors. With respect to anaesthesia, boththe effects of the agents and the skills of the practitioner are important. Similarly, thesurgical procedure itself, as well as the surgeon’s skills, impact on perioperative risk.From the patient’s perspective, the question remains whether the co-existing diseaseraises the probability of complications to a level such that the benefit of the surgery isoutweighed by the risk. Perioperative risks in the outpatient setting can be broadlyclassified into four categories:

1. risk of surgery2. risk of anaesthesia3. patient and procedure as risk factors4. risks related to the establishment (hospital/day centre, etc.)

Strategies for the reduction of the risks discussed are consequent to avoidance ofthe factor increasing the risk and become apparent as one reads on. It is important torealize at the outset that it is a combination of factors that increases (or decreases) theperioperative risks, and avoiding one drug or technique in a given patient may not affectoutcome. Also, some risks can be quantified to some extent depending on acombination of type of surgery, patient factors and anaesthetic drugs and techniques,e.g. post-operative nausea and vomiting, but because of the absence of large studies insimilar ‘at-risk’ patients undergoing a specific procedure using a standard anaesthetictechnique, it is difficult to be sure of the specific risk in a given patient. Therefore, someof the conclusions drawn by the author in this chapter are based on generalinformation, sometimes based on studies in inpatients, and all too often on olderstudies using drugs and techniques which are no longer used today! Until better

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procedure-specific, prospective studies in ambulatory patients are published, theconclusions here should be considered only as guidelines.

Risk of surgery

It is well known that every operation is associated with an inherent risk which dependsnot only on the extent of the surgery but even on the surgeon performing theoperation. Below are some examples from the literature where surgery-related factorshave affected perioperative complications during ambulatory surgery.

1. In a multi-centre study of 1183 patients, the recurrence rate after hernia surgery wascompared between laparascopic and Shouldice operation. An independent observerscored each surgeon’s performance on a 9-grade scale in this 5-year follow-up study.There was no difference in recurrence rate, but it ranged from 4.5 to 12.7%(laparascopic) and 1.6 to 13.6% (Shouldice). The risk factors for recurrence wereASA II– III patients, low surgeon performance score, and severe post-operative painafter Shouldice operation. For individual surgeons the risk of recurrence varied from0 to 22.7% (laparoscopic) and 0 to 19% (Shouldice).5 This study would confirm thatno one would prefer to be operated upon by an inexperienced surgeon!

2. There is ample evidence from a number of well-performed studies that hospitaldischarge times, as well as return to work, are much shorter after laparoscopiccholecystectomy compared to open cholecystectomy.6 However, there is a slightlygreater risk for injury to the common bile duct during laparoscopic surgery.7 Thiscreates a major ethical problem for the surgeon as well as the insurance companies.It is reasonable to assume that the patient would prefer to have the minimum risk ofa post-operative complication, whatever the cost to the insurance company. Thesurgeon then has to decide which method is preferable, keeping in mind the opposinginterests of the actors involved. In this situation, it is often the skill of the surgeonperforming the procedure that outweighs the other risks.

3. Although many invasive arthroscopic procedures—including meniscus and ligamentrepairs—result in better outcome for patients, one recently published study hasshown that ‘sham’ arthroscopy on patients results in an outcome similar to that oftrue arthroscopic surgery for certain knee diseases, thus questioning arthroscopy asa tool for patient management.8 In this situation, the surgeon should take intoconsideration both the anaesthetic and surgical risks in relation to the benefit to thepatient when deciding whether to perform the procedure.

4. Tonsillectomy is associated with a 1-in-250 to 1-in-500 rate of emergencyreadmission for bleeding within 24 hours in healthy children.9 It is important todetermine whether this represents safe or unsafe practice and whether the rates of‘morbidity’ are acceptable as practices are diffused.

Risk of anaesthesia

Mortality directly attributable to anaesthesia is low (1 in 30 000 to 1 in 185 000anaesthetics)10,11, and anaesthesia-related mortality following ambulatory surgicalprocedures is even lower.12,13 Considering this low rate, any study would have to beenormous in order to detect anaesthesia-related mortality. Such a study would requireinformation from a large number of sites, or cover many years (or decades) from asingle institution. Amongst the causes cited to be important in anaesthesia-relatedmortality include aspiration and myocardial infarction. With the increase in the number

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of sicker and older patients undergoing ambulatory surgery, it is likely that we shall seean increase in mortality in the future.

Morbidity—specifically major morbidity—has been the focus of attention forphysicians in the outpatient setting. Morbidity could be defined as the need foradmission or readmission after ambulatory surgery. The time horizon for readmissionmust be evaluated. Certainly, readmissions within 24 hours are of greatest concern, butadmissions within 1 week may still be related to perioperative care. The rates inoutpatient centres must be benchmarked and compared with those of inpatient centresfrom this national database, and the primary cause for readmission must be determined.In this manner, a ‘safer’ perioperative experience can be defined. Morbidity could alsobe defined as the incidence of major or minor complications. Major complicationsfollowing ambulatory surgery include myocardial infarction, pulmonary embolism,respiratory failure and cerebrovascular accidents.14 Warner et al found that theincidence of major morbidity following ambulatory surgery was low, with an overallincidence of 1 in 1455.13 Whether pre-existing disease affects post-operative morbidityremains uncertain.15,16 With the rapid growth in ambulatory surgery in the past fewyears, it is imperative not to combine the perioperative anaesthesia risk associated withdifferent operations into a single risk factor. A better approach would be to do anational (or local multi-year) surveillance to determine the safety of a given procedure.With the increased use of meta-analysis, it has become common in recent years tostudy procedure-specific morbidity and mortality. One organization that has used amulti-discipline, procedure-specific approach to the assessment of best-practicemanagement is the PROSPECT group.17 (More information on this can be obtainedfrom the website: http://www.postoppain.org.) In the only documented evidence-basedapproach, they have studied and defined, amongst others, risk factors for ambulatorylaparoscopic surgery. The group is presently working with inguinal herniorrhaphy inorder to define best evidence from existing literature on this subject.

Minor complications following outpatient procedures performed under generalanaesthesia are common. In one recent meta-analysis of the literature, the authors foundthat the use of total intravenous anaesthesia compared with inhalation anaesthesiareduced the risk of PONV significantly.18 Wu and colleagues reviewed the literature andidentified post-discharge symptoms after outpatient surgery.19 They found that theoverall incidence of post-discharge pain was 45%, nausea 17%, vomiting 8%, headache17%, drowsiness 42%, tiredness or fatigue 21%, myalgia 31% and sore throat 37%, andthese represented the commonest symptoms. The presence of these symptoms maypotentially impede resumption of normal daily activity and function, thereby affectingoutcome. However, the extent to which these symptoms increase the burden onpatients, their caregivers, or society remains unclear. In a recent study, the authorsperformed a meta-analysis of the literature in order to identify whether the use ofprophylactic anti-emetics affect the risk of post-discharge nausea and vomiting(PDNV).20 They found a reduction in the incidence of PDNV when using ondansetronor combination therapy. Therefore, it would be important to consider thesemanagement strategies when assessing the individual patient with multiple risk factors.

Morbidity following regional anaesthesia procedures varies tremendously betweenstudies. Complications following spinal anaesthesia have been reported to vary from0%21 to 1 in 5900.22 Corresponding figures for epidural anaesthesia are 1:1000 forminor complications and 1:3600–1:11 000 for irreversible lesions.23–25 A recent studysuggests a much higher incidence of major irreversible complications, with an incidenceof 1:2834 for spinal and 1:3077 for epidural blocks.4 In this case series, five of the 22patients underwent knee arthroscopy and one patient underwent transurethral

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resection of a bladder tumour, all under spinal anaesthesia. These patients could beconsidered as outpatients today, and three of the six patients had permanentirreversible injury. In one case, the injury was disabling, requiring the use of crutcheseven after 3 years. In three of the six cases, the patients were readmitted due tosymptoms following discharge home. Peripheral nerve blocks are associated with thehighest incidence of systemic LA toxicity (7.5 per 10 000) and the lowest incidence ofserious neural injury (1.9 per 10 000).26 Intravenous regional anaesthesia is one of thesafest and most reliable forms of regional anaesthesia for short procedures on theupper extremity. Ophthalmic surgery is particularly suited to regional anaesthesia.However, serious complications—including retrobulbar haemorrhage, brain stemanaesthesia and globe perforation—have been reported, but are uncommon in skilledhands.27,28

Patient and procedure as risk factors

It has been well documented that patient disease is one of the strongest predictors ofperioperative morbidity and mortality.29 With respect to patient factors that couldaffect perioperative risk, most studies have focused on cardiovascular risks, and someon respiratory risks. Unfortunately, most of these studies are in inpatients, and toextend the findings from the inpatient to the outpatient population may not reflect truerisk factors.

There is adequate evidence in the literature to show that a higher ASA class isassociated with greater post-operative mortality and morbidity. However, these studiesare based on inpatient populations and using anaesthetic techniques practised morethan 20 years ago. Since a vast majority of the outpatients are in the ASA I–III group andwell controlled on their medication, no studies have demonstrated increasing mortalitywith increasing ASA status. In addition, there is a lack of correlation between ASAstatus and cancellations, unplanned admissions and other perioperative complicationsin outpatient surgery.30 Similarly, increasing age has not been demonstrated to increasemortality and morbidity in outpatient surgery and should therefore not be consideredas a risk factor. Patient factors that have been shown to be associated with increasedrisk in outpatient surgery are obesity, the premature infant and a recent myocardialinfarct (,1 month). Patients with sleep apnoea syndrome—which was until recentlyconsidered as a risk factor for outpatient surgery—are increasingly being successfullyoperated on as outpatients. Some of the other known patient factors that have beenshown in different studies to be associated with a higher incidence of perioperativecomplications include the following.

1. Smoking has been shown to be associated with an increased risk of respiratorycomplications and post-operative wound infection in ambulatory surgerypatients.31

2. Obstructive sleep apnoea in the ambulatory surgery setting has become a moresignificant concern in recent years because its identification and recognition are acritical part of pre-operative patients’ risk assessment. Ambulatory patients withidentified obstructive sleep apnoea will require a planned course of care (seebelow).32

3. Hypertension can predict the occurrence of any intraoperative event andintraoperative cardiovascular events.

4. Obesity has been shown to predict intraoperative and post-operative respiratoryevents, and smoking and asthma could predict post-operative respiratory events

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in one study.33 However, in another study the authors found that morbid obesitywas not a contraindication to gynaecological laparoscopy.34

5. Among the predictive factors found for unanticipated hospital admissions weremale sex, ASA status II and III, long duration of surgery, surgery finishing after 3pm, post-operative bleeding, excessive pain, nausea and vomiting, and excessivedrowsiness or dizziness.35

6. The nature of the procedure is an independent risk factor. The American Societyof Anesthesiologists Task Force on pre-anaesthesia evaluation suggested a three-grade system for pre-operative risk assessment based on the planned surgicalprocedure: low-risk surgery—minimal physiological stress and risk to the patientindependent of medical status; medium-risk surgery—moderate physiologicalstress, minimal blood loss, fluid shift or post-operative change in normalphysiology; and high-risk surgery—significant perioperative and post-operativephysiological stress.36 Thus, depending on the planned procedure and theconsequent perioperative risk, patients may be assessed prior to the day ofsurgery or on the morning of surgery. Clearly, a patient with a low-risk medicalstatus in the ASA I–II group undergoing a low-risk surgical procedure may beevaluated on the morning of surgery and may not benefit from a visit to the pre-anaesthetic clinic. However, a high-risk medical status patient in the ASA III– IVgroup undergoing a medium- to high-risk procedure is a definite candidate forpre-operative evaluation prior to planned surgery.

Risks related to the establishment

Anaesthetic risk has decreased dramatically during the past decade. However,perioperative safety is ill defined when the surgical procedure is performed in thephysician office. Perioperative risk may vary depending on the surgical location(hospital, freestanding unit, or physician office). Elective surgical procedures aremoving from hospital-affiliated and freestanding ambulatory centres to the physicianoffice. The complexities of this growth in ambulatory surgery from the hospitalsetting to the physician office are enormous, and extremely challenging. Not only isthe availability of specialists—e.g. cardiologists to diagnose complex arrythmias orinsert pacemakers when needed—limited (if not completely absent) in office-basedsurgery, but equipment to handle intraoperative or post-operative emergencies maynot be available. Added to this, the problems of unanticipated admissions requiringhospital beds (unplanned) and limited transport facilities (ambulances) leading topossible delays in admission must be considered. In the United States, regulation ofoffice-based surgery is now being addressed by specialty organizations. Acomprehensive study of perioperative risk for patients receiving office-based

surgical care is needed before further expansion of this is accepted.37 In a recentstudy, Vila et al studied office-based versus ambulatory centre-based surgery inFlorida38. The death rate per 100,000 procedures performed was 9.2 in offices and0.78 in ambulatory surgery centers. They concluded that there was approximatelya 10-fold increased risk of adverse incidents and death in the office setting. If alloffice procedures had been performed in ambulatory surgery centres, approxi-mately 43 injuries and 6 deaths per year could have been prevented. This studywould suggest that an accrediting system must be available and performed regularlyin order that there is added risk to the patient depending on the site where theoperation is being performed. Such an accrediting system should have clearly laid

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down rules and regulations as well as prerequisites in order for the facility toperform surgery.

As the population presenting for day-case surgery and anaesthesia increases, so doesthe challenge of adequate pre-operative assessment. Not only is the establishmentrequired to provide documented policies for pre-operative assessment of patients, butalso who should perform this assessment is equally important. For instance, although anelectrocardiogram (ECG) is frequently performed, its value in day-case surgery remainsunproven. In one study, 1185 patients presenting for day-case surgery were assessed.39

Of these, 154 (13%) were referred for ECG according to well-recognized criteria for theprediction of coronary artery disease. A significant abnormality was noted in 26% ofECGs, most frequently in patients referred with hypertension. There was a goodcorrelation between the reports of the anaesthesiologist and cardiologist. Only 20% ofthose patients with an abnormal ECG had their surgery postponed. No adverse eventsoccurred in patients proceeding to surgery despite the abnormalities. The authorsconcluded that a resting electrocardiogram is of limited value in risk stratification ofpatients undergoing day-case surgery (anaesthesia). In another study, it was found thatunanticipated intraoperative events (UIE) were more likely to occur in non-clinic patientsthan in those who went via a pre-operative anaesthesia clinic.40 Thus, the role of the pre-operative clinic could be considered to be important, particularly in patients at risk.

WHAT ARE THE STRATEGIES AVAILABLE FOR RISK REDUCTION?

Optimization of a patient’s condition usually results in reduction in perioperativecomplications. In order to achieve this, it is imperative to diagnose disease states thatcould lead to an increase in perioperative morbidity. Data on sick patients undergoingambulatory surgery are limited, and hence some of the conclusions in this chapter arebased on experience from inpatients. Complications related to anaesthesia arecommonly related to the cardiovascular or respiratory systems, and therefore theseaspects will be highlighted in this chapter. The role of the pre-operative clinic in theearly diagnosis and prompt treatment of the medically compromised patient isimportant, specifically because the patient scenario in ambulatory surgery is steadilychanging from the completely healthy patients 20 years ago to the increasinglydebilitated patients today. There are adequate data to show that healthy patientsundergoing ambulatory surgery do not have a higher mortality than inpatients.12,13,16

What about the increasingly sick patients that are today being accepted for ambulatorysurgery? Some data are available in these patients, and some of the methods used todecrease the risks by pre-operative optimization are known. These strategies can bedivided into the following broad categories:

1. strategies for reduction of general risks2. strategies for reduction of cardiovascular risks3. strategies for reduction of respiratory risks4. strategies for reduction of other risks

It is important to stress here that the role of the health-care experts (surgeons,anaesthesiologists and nurses) is to be able to first identify the patients at risk andsubsequently to offer known strategies that can reduce these risks. A health-caresystem that is weak at identifying patients at risk would also be unable to introduce

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protocols to reduce the risks in these patients. A general plan for patient managementand risk reduction is shown in Figure 1.

Strategies for reduction of general risks

Common strategies that would apply to all patients in reducing perioperative risksduring ambulatory surgery could include the following.

Patient Surgery

Anaesthesia Establishment

Perioperative Risk

Identification in preoperative clinic

Early postoperative intervention

REDUCE

MANAGE

IMPROVED PATIENT OUTCOME

Figure 1. A general plan for patient management and risk reduction.

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Control of weight

Some of the complications related to obesity can be avoided by measures to reduceweight in the morbidly obese patient. Higher body mass index (BMI) is associated withgreater anaesthetic risk; specifically, a BMI . 35–40 should not be accepted forambulatory surgery. In March 1992, the Royal College of Surgeons in England issuedguidelines for day-case surgery and suggested that patients with a body mass index(BMI) . 30 were deemed unsuitable for operations to be performed as a day case.41

These guidelines have recently been questioned in the UK, with most hospitalsaccepting a BMI # 34 for day surgery.42 One study published recently did not find anysignificant increase in unplanned admission rates or post-operative complications inmorbidly obese patients with a BMI . 35.43 Thus, the literature appears to besomewhat controversial in this area.

The pre-term child

Ambulatory surgery in full-term (.37 weeks) babies should be avoided if the post-conceptual age is ,48 weeks.29 In the pre-term baby (,37 weeks gestational age)ambulatory surgery should be avoided unless the post-conceptual age is .52–60weeks.29,44 Newborn babies require a higher concentration of inhalation anaestheticsfor adequate anaesthetic depth compared to children and adults. During the first weekof life, the elimination half-life of morphine is more than twice as long as in olderchildren or adults, and is even longer in premature infants.45

Control of smoking

Anaesthesia-related complications in the chronic smoker are well known, and recentevidence seems to indicate delayed wound and bone healing and also delay in homedischarge in chronic smokers compared to non-smokers.46 Should smoking beforbidden on the morning of the operation? There are no studies in the literature thathave shown increased morbidity or mortality as a consequence of smoking on themorning of surgery. However, smoking has been shown to be associated with anincreased risk of respiratory complications and post-operative wound infection inambulatory surgery patients.47 Transdermal nicotine reduces perioperative withdrawalsymptoms when smoking is forbidden. However, it could significantly increase heartrate and should not be used if tachycardia is potentially dangerous, as in patients withischaemic heart disease.48 In children undergoing general anaesthesia for inguinal herniarepair, exposure to environmental tobacco smoke was associated with an increasedfrequency of respiratory symptoms during emergence from anaesthesia and duringpost-operative recovery.49 Chronic obstructive lung disease as a complication ofchronic smoking is addressed later in this chapter.

Optimization of chronic health status

Well-controlled patients with pre-existing diseases like asthma, diabetes, hyperten-sion, coronary artery disease, etc. are not at an increased risk for complicationsduring ambulatory surgery. Thus, it is important to control the chronic health statusand optimize medical therapy prior to planned ambulatory surgery. The role ofthe pre-anaesthetic clinics (PAC) in this respect is increasingly important.Perioperative complications can be reduced in the ambulatory centre through thejudicious use of well-defined protocols in the PAC. Increasingly, the role of

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the perioperative anaesthetic nurse is becoming important in the screening ofpatients prior to surgery. At the Johns Hopkins Ambulatory Medical Center inBaltimore, a trained anaesthetic nurse routinely screens all patients prior toambulatory surgery and the anaesthesiologist is involved in the work-up of the sickpatients prior to surgery. This system has existed successfully for more than 10years and can be a model for others wanting to introduce quality improvement inthe ambulatory setting.

Prevention of aspiration

Aspiration of stomach contents at the time of induction of anaesthesia continues to be amajor cause of death following anaesthesia. Strict adherence to nil-by-mouth guidelinesis important for the effective working of an ambulatory centre. Perioperativecomplications—e.g. regurgitation and bronchial aspiration—can be reduced throughproper implementation of these guidelines. In patients with gastro-oesophageal reflux,the use of H2-receptor antagonists or proton-pump inhibitors prior to induction ofanaesthesia is increasingly recommended. When appropriate, the use of a nasogastrictube is strongly recommended.

Adequate information and instructions

It is imperative to give patients full and detailed instructions with explanations ofwhat to expect perioperatively, and how to avoid post-operative complications.Simple advice as to the importance of early mobilization leading to reduction inthe incidence of post-operative deep vein thrombosis, proper hygiene of thewound in decreasing the risk of infection, and the importance of taking analgesicmedication as directed in preventing severe pain, are all becoming increasinglyimportant in reducing complications and perioperative risks in the ambulatorysurgical patient.

Strategies in reduction of cardiovascular risks

Probably the single most common cause of perioperative complications inambulatory surgery patients is cardiovascular mishaps. In Warner’s study onambulatory surgery patients13, the two patients who died from medical causes werethose who had a myocardial infarct more than 1 week after the anaesthetic. Cardiaccomplications have been described with both general and regional anaesthesia, inhealthy as well as sick patients, and are in many cases avoidable. Bradycardiafollowing the induction of general anaesthesia with propofol has been well describedin the literature. In controlled clinical trials, propofol significantly increased the riskof bradycardia compared with other anaesthetics (number-needed-to-harm 11.3).50

In paediatric strabismus surgery the number-needed-to-harm was 4.1. One of 660patients undergoing propofol anaesthesia had an asystole. The risk of bradycardia-related death during propofol anaesthesia in this study was estimated to be 1.4 in100 000. Thus, glycopyrrolate or atropine could be recommended routinely duringinduction of anaesthesia with propofol, specifically in children. Propofol, by virtue ofsystemic vasodilation, may also produce a significant fall in blood pressure,particularly when combined with opiates, and should probably be avoided in cardiacpatients undergoing ambulatory surgery.29 Hypotension is also common whenremifentanil is used as an opiate instead of fentanyl.51 Thus, a combination of

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propofol and remifentanil is a risk factor in the cardiac patient undergoingambulatory surgery. The use of beta-blockers prior to induction of anaesthesia—particularly in cardiac patients undergoing non-cardiac surgery—has been extensivelydebated, and it appears that there are benefits in reducing cardiac complicationsperioperatively52, even following discharge, and is today recommended as a routine.There appears to be no evidence in the literature to suggest that routinely admittingwell-controlled cardiac patients after ambulatory surgery is beneficial. According to arecent meta-analysis of the literature on cardiac patients undergoing non-cardiacsurgery, the continued use of calcium antagonists on the morning of surgery appearsto reduce major morbid events, myocardial ischaemia and supraventriculartachyarrythmias.53 Beta-blocker therapy started 7 days prior to planned surgeryhas been shown to reduce morbidity in cardiac patients undergoing non-cardiacsurgery.54 Whether this can be stretched to include ambulatory surgery patientsundergoing minor surgery remains unknown. Both the choice of anaesthetic(regional versus general anaesthesia), as well as the type of anaesthetic (inhalationversus intravenous) is still controversial in high-risk cardiac patients. Nosingle anaesthetic technique has been shown to result in improved patientoutcome in these patients, and therefore risk reduction strategies should bedirected towards those based on general knowledge, i.e. avoid hypotension,tachycardia, oxygen desaturation and anaemia, all of which have been shown to beassociated with increased risk of myocardial ischaemia. Patients with haemodyna-mically significant aortic stenosis are probably not appropriate candidates forambulatory surgery and warrant further investigation. This applies even to theelderly patient where auscultatory findings consistent with aortic stenosis needsfurther assessment.

Strategies for reduction of respiratory risks

Risks associated with or caused by aspiration and the consequences of smokinghave already been addressed in the previous section. Complications associated withthe respiratory system are often related to pre-existing diseases, and theoptimization of these diseases is the most important step in pre-operativepreparation for ambulatory surgery. Rare but relevant respiratory complicationswhich are often iatrogenic include over-dosage of opioids leading to respiratorydepression, pneumothorax from accidental pleural puncture following brachialplexus block (infraclavicular or interscalene approach) or paravertebral block,diaphragmatic paralysis from interscalene approach to the brachial plexus,accidental dental injury and subsequent aspiration into the trachea/bronchus duringintubation, and nasal bleeding during nasotracheal intubation leading to aspiration ofblood. All of these are preventable injuries and require constant attention to themeticulous use of needles and equipment during anaesthesia. The rare case ofpressure pneumothorax due to rupture of emphysematous bulla is unlikely to bepreventable but when due to excessive intrathoracic pressure from faultyequipment can certainly be avoided. Poor pain management post-operativelyleads to difficulty in coughing, specifically in patients undergoing abdominalsurgery, and this in turn can lead to atelectasis and lower respiratory tractinfections. It is imperative, therefore, to start adequate pain managementtechniques early. This is even more important in the patient with a compromisedrespiratory status, e.g. chronic obstructive lung disease (COLD), kyphoscoliosis,myasthenia gravis, etc.

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Patients with asthma are at risk of an exacerbation during anaesthesia andsurgery. Not only is it vital that they are in optimal condition prior to induction ofanaesthesia, but also morning bronchodilators should be taken routinely andtriggering agents avoided whenever possible. Drugs known to cause histaminerelease—e.g. morphine, atracurium, pancuronium, etc.—should be avoided, specifi-cally in the very sensitive patient. The value of pre-operative spirometry should notbe discounted to assess for evidence of reversible bronchial constriction as well as inthe evaluation of any change in post-operative status. Since most inhalationanaesthetics are potent bronchodilators, these should be used perioperatively as apart of the anaesthetic regimen.

COLD is a special problem, and most patients with severe COLD undergoing allexcept the most minor surgery should preferably be admitted post-operatively.These patients need to be optimized in their need for medication and oxygentherapy, and some require non-invasive ventilation techniques in order to achieveacceptable pre-operative status. Spirometry is essential in the workup towards theoperation, and a blood gas analysis prior to operation can be valuable in determiningchronic health status. Whenever possible, loco-regional anaesthetic proceduresshould be and have been used safely in these patients. For details on themanagement of these patients, the reader is referred to special textbooks on thissubject.

Obstructive sleep apnoea is defined as cessation of airflow for a minimum of10 seconds despite persistent respiratory effort by the abdomen and rib cage. It ischaracterized by decreased airflow and associated oxyhaemoglobin desaturation of.3%. Evidence as to best practice management of these patients is lacking in theliterature, but it would be prudent to use regional anaesthetic techniques and peripheralblocks whenever possible. High central blocks should naturally be avoided since theymay exacerbate an already compromised pulmonary system.29 Laparoscopic pro-cedures appear to produce little sleep disturbance compared to open laparotomy55,which could be related to the lesser morphine consumption.

Strategies for reduction of other risks

Risks associated with the establishment and their prevention or reduction is ofparamount importance. Lack of availability of full-time anaesthesiologists in anambulatory surgery centre can sometimes be hazardous since all personnel are notappropriately trained to deal with emergencies. Such a scenario is not uncommon inoffice-based surgeries, and a recent report showing a mortality rate of 1 in 5224following liposuction operations in the USA is cause for concern.56 Many of thesepatients died of thromboembolism but surgical complications including organperforation was not uncommon. Thus, education and training are essential in orderto reduce perioperative mortality.

The use of clinical pathways appropriate not only for the type of operation but eventaking into consideration underlying disease has been shown to reduce morbidityfollowing transurethral resection of the prostate and is likely to do so even afterambulatory surgical procedures. Algorithms for the management of the sick patients ina standardized way are important, specifically when the person doing the assessment ofthe patient is not the same as the person responsible for patients’ subsequentmanagement. Clear verbal and written instructions should be given to the patient priorto discharge home, and these should include the appropriate management of pain,PONV and other minor complications following surgery. Prophylactic management of

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the patient at high risk of PONV using anti-emetics and total intravenous anaesthesiawith propofol is important in reducing post-operative as well as post-dischargemorbidity from PONV.

The use of local anaesthetics subcutaneously into the surgical wound and intodeeper tissue planes (intraperitoneally) has reduced pain following ambulatorysurgery. Catheter techniques where the patient is discharged home with a catheterin place and an elastometric pump with local anaesthetic for infusionwhen desired (home-pump, I-Flow, etc.) have improved pain managementsubstantially, thereby reducing post-operative morbidity and improving patientsatisfaction.57,58 The use of intraarticular morphine and local anaesthetics for post-operative pain management after arthoscopic surgery, although controversial, has inmany studies been found to reduce pain intensity post-operatively.59,60 These aswell as other newer methods and drugs are likely to reduce pain and improvepatient satisfaction in the future and thereby lead to a reduction in perioperativemorbidity.

With respect to regional anaesthesia, the availability of better needles (spinal,peripheral blocks) has led to a reduction in the incidence of headache andperipheral nerve injuries, respectively. Following the withdrawal of lidocainefrom many parts of the world for spinal anaesthesia, newer methods usingsmall doses of bupivacaine combined with clonidine or fentanyl have beenused successfully during ambulatory surgery, including gynaecological laparoscopy.The use of nerve stimulators in routine practice has helped to improve thesuccess rate of peripheral blocks, and the availability of video films has helped inthe training of residents in the use of highly successful and efficient regionalanaesthesia services during ambulatory surgery, thereby reducing perioperativemorbidity.

Finally, risk reduction is a team effort, and it is therefore imperative that there isalways a clear dialogue between the different partners that are involved in patientmanagement, not least the patient himself/herself. Whenever in doubt, discussionswithin the team involved, or outside, would help in reducing perioperative risks.Specifically, a planned management strategy for the individual at-risk patient should beinitiated early in order to achieve best results. This would require a close collaborationbetween the surgeon, anaesthesiologist, pre-operative anaesthetic clinic staff and theanaesthetic nurse.

SUMMARY

Perioperative risk reduction is a challenge for the physician as well as the health-caresystem. In order to be able to have the best possible outcome for the patient, it isimportant to establish routines for the identification of patients at risk of perioperativecomplications. Subsequently, a clear pathway for management of these patients needsto be employed. This should preferably be based on clear evidence from the literature,and needs to be reassessed periodically. Not only should this be procedure-specific, butalso (pre-existing) disease-specific whenever possible. Using these guidelines, it shouldbe possible to offer the patient best outcome, thereby reducing perioperative risks inthe ambulatory setting.

688 A. Gupta

Practice points

† perioperative risk reduction in the ambulatory surgical patient is based on riskidentification. In order to effectively use strategies to detect risks, the use of apre-anaesthetic clinic has been shown to be important. Low-risk patients canbypass the pre-anaesthetic clinic and be assessed in the hospital on the day ofsurgery without affecting outcome negatively. High-risk patients need always tomeet an anaesthesiologist a few days to a few weeks prior to the operation inorder to be adequately prepared and investigated and consequently in optimalcondition on the day of surgery

† having identified the patient at risk, strategies need to be employed in order toreduce these risks. Many of these strategies are based on studies in inpatientsbut could apply to the outpatient and are specifically directed to reducingcardiorespiratory morbidity and mortality, which are the commonest causes ofperioperative complications

† general factors that may be of importance in risk reduction, include choosingthe correct patient for outpatient surgery, providing written instructions forthe time for correct intake of food and beverages prior to surgery, as also forthe management of post-operative pain, PONV and other commoncomplications at home

† risk factors attributable to the establishment, such as having adequate staff withappropriate knowledge; using clinical pathways and algorithms for patientassessment would go a long way in reducing perioperative complications

† lastly, a team approach should be the guiding slogan, particularly in the patient atrisk, and strategies to reduce these risks should be well planned, together withthe patient, prior to surgery

Research agenda

† with the rapid increase in the number of patients undergoing operations on anoutpatient basis, more data are now available and should be used to formulatebetterpolicies forpatientmanagement in theoutpatient setting.Transferringdatafrom the inpatient to the outpatient setting may not always be appropriate. Riskidentification is the first step in achieving this goal, and it should specificallyaddress the ambulatory surgical patient. Using better statistical methods and alargedatabase of ambulatory surgical patients, itmaynotbedifficult to stratify riskaccording to known (and sometimes unknown) factors. These risks shouldpreferably be stratified according to the typeof surgery and anaesthesia, using theapproach used by the PROSPECT group. Having identified these risk factors, it isimportant to test whether they hold and are consistent in large prospectivestudies. The next step wouldbe to assess differentmethods to reduce these risks.Whenappropriatemethodsare identifiedandshowntobeassociatedwithaclearrisk reduction, they need to be incorporated into daily practice in the individualpatient. Thus, the strategies for risk reduction in the ambulatory surgical patientneed to follow a process of identification, modification and reassessment of newmethods in order to provide the best possible outcome for the patient. Thesenew methods should be evidence-based whenever possible and supported byprospective studies, preferably double-blinded and randomized

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