Preoperative considerations, anaesthesia and analgesia

Assessment of operative fitness and perioperative risk

Elective preoperative assessment takes place in several stages beginning at the point of referral for surgery ( Fig. 7.1 ). A good referral letter should include details of the presenting complaint and the patient’s general health, comorbidities and current medication. The first contact with the surgical team is usually in the outpatient clinic, and this consultation may lead to a decision to offer surgical treatment. When considering whether a patient should have surgery, the surgeon should consider whether the patient is medically fit enough to undergo the proposed procedure and if the benefits of the surgery outweigh the potential risks and severity of any complications. Regardless of whether a decision is made to operate or pursue alternative therapy, it is now widely recognised that this point represents a ‘teachable moment’ whereby modifiable patient factors can be identified and a personalised prehabilitation programme may be implemented.

When making the decision to operate, the risks and potential benefits of surgery should be weighed against those of alternative or no treatment. Where possible, patients should be fully involved in these decisions. The purpose of preoperative assessment is to identify and treat any comorbid conditions, estimate perioperative risk, optimise the patient’s physical condition and medically and psychologically prepare the patient for surgery. Preoperative assessment may take place in a dedicated assessment clinic a few weeks before surgery and culminates in the admission to hospital on the preceding day or, more usually, on the actual day of surgery.

Perioperative medicine

Perioperative medicine involves coordination of expertise from a multidisciplinary team including doctors from other specialties such as anaesthesia and surgery. This also includes medical specialties such as cardiology, respiratory, renal medicine, care of the elderly and primary care. These teams can improve the perioperative management of high-risk patients, reduce the likelihood of complications and optimise the management of complex disease and its interaction with major surgery. Surgeons and anaesthetists may not have detailed knowledge of the management of specific complex diseases, and this approach ensures patients receive the best possible disease management before undergoing surgery. Perioperative medicine extends throughout the whole of the patient’s operative journey.

Shared decision making

In some circumstances, the risks of major surgery can be very high and the planned operation not in the patient’s best interests. This may be due to a combination of the presence of comorbidity, increased risk of complications and the magnitude of the proposed surgery. The patient may need to spend a considerable period in critical care or hospital following surgery and surgical treatment may not improve (or even decrease) quality of life. Shared decision making with the patient allows consideration of nonsurgical options such as chemo/radiotherapy or palliation (e.g., for cancer surgery) or physical therapy (e.g., for joint replacement surgery), and to choose a course of action that best meets patients’ hopes and expectations. Shared decision making about postoperative care, including critical care (with an advanced directive if appropriate), can be vital in emergency surgery and might better meet patient expectations of survival with acceptable quality of life. High-risk patients being offered major surgery in any setting must be fully counselled about the risks of, and the alternatives to, surgery.

Preoperative assessment process

Thorough and timely preoperative assessment is essential to avoid the risks and costs of cancelled or delayed surgery. Good quality assessment and appropriate optimisation prior to admission mean that many patients can be admitted on the day of surgery. Thorough preoperative assessment will involve a detailed medical history, systematic enquiry, physical examination and then laboratory, radiologic and other investigations as directed by clinical history, examination findings and the nature of the surgery. It is sometimes helpful to classify surgery by magnitude, e.g., the system proposed by the National Institute for Health and Care Excellence ( Table 7.1 ).

Preoperative assessment can be a complex process. For patients with minimal comorbidities undergoing low-risk surgery, it can be undertaken by a preassessment nurse and may be performed by telephone or even be self-administered using an online questionnaire. However, a review by a consultant anaesthetist at a preassessment clinic should be requested prior to admission where there is increased risk (e.g., major surgery, advancing age or significant comorbidity), fitness for surgery is in doubt, where there are specific anaesthetic issues requiring assessment or if the surgery itself is particularly high risk. Any issues can then be communicated to the anaesthetic team involved in delivering anaesthesia.

Patients having surgery are classified according to the American Association of Anesthetists–Physical Status (ASA-PS) score. This scoring system was developed in 1963, and although it is a crude estimate of anaesthetic risk with a high rate of interobserver variability, is still in ubiquitous use. It consists of six categories, with the suffix ‘E’ denoting emergency surgery ( Table 7.2 ).

On the day of surgery, both the surgeon and anaesthetist should reassess the patient and identify outstanding issues and any changes in their condition. All investigation results should be available, as well as necessary blood products and special equipment. Details of the anaesthetic should be confirmed, including postoperative analgesic strategies, taking into account patient preferences wherever possible. An overview of the preassessment process is outlined in Fig. 7.1 .

In urgent and emergency situations, this process is condensed, and the timing of surgery is crucial. The surgeon must determine which interventions will optimise the patient’s condition while avoiding deterioration due to unnecessary delay.

A detailed preoperative assessment should consider the following systems.

Anaesthetic assessment

Preoperative investigations

For many patients in good health undergoing relatively mild surgery, preoperative investigations are not required. For those with more severe comorbidities or who are undergoing major surgery, full blood count, coagulation screen, urea and electrolytes, electrocardiograph (ECG) or tests of respiratory function may be needed. Tables 7.4, 7.5 and 7.6 suggest where it is appropriate to routinely order these tests before surgery.

Cardiopulmonary exercise testing

Formal assessment of functional capacity is increasingly used to stratify perioperative risk. Assessment of functional status has been part of routine preoperative history taking for many years, and self-reported poor exercise tolerance has been shown to correlate with increased perioperative risk.

More formal risk assessment tools and scoring systems use a combination of this history with a number of investigations such as ECG, echocardiography, chest x-ray and blood tests. However, such traditional tools look at individual organ systems in a state of rest. Investigations of physiologic reserve such as exercise ECG and stress echocardiography focus predominantly on single organ systems. Cardiopulmonary exercise testing (CPEX or CPET) provides a safe assessment of a patient’s functional status and the relative contribution of cardiac, pulmonary and metabolic function ( Fig. 7.2 ). It demonstrates the patient’s ability to respond to the stress of major surgery and allows stratification of risk according to cardiopulmonary reserve. It has become an important part of the preoperative risk assessment of patients for major or high-risk surgery.

Physiologic variables, including ECG, noninvasive BP and SpO2 as well as continuous gas analysis, are monitored during incremental exercise on a treadmill or exercise bike. Exhaled gases are collected and analysed to allow calculation of oxygen consumption and carbon dioxide production. The anaerobic threshold (AT) marks the point at which oxygen demand is greater than supply and anaerobic metabolism occurs. This can be seen in graphical representation of the variables when displayed in a nine-panel plot. The AT provides a measure of the functional capacity of the patient, and a low AT has been shown to be associated with an increase in postoperative complications. As well as providing information on the suitability of patients for some high-risk procedures, it can also be used to determine whether a patient should be electively admitted to high-dependency or ICUs postoperatively.

Multimodal prehabilitation

There is growing evidence for the benefit of preoperative exercise prior to surgery in reducing perioperative morbidity by improving cardiorespiratory performance. The introduction of formalised enhanced recovery after surgery (ERAS) pathways in the 1990s has led to improvements in the intraoperative and postoperative care of patients with an aim to reduce the length of hospital stay following surgery and expedite the return to normal activity. However, it is only recently that the focus is shifting to the preoperative period in an effort to optimise patients before they come to surgery ( Fig. 7.3 ).

Undergoing a major surgical procedure is associated with significant physiologic stress, and there is now an understanding that increasing functional capacity prior to surgery is associated with better outcomes. This is of particular relevance to older patients who have reduced physiologic reserve and are particularly vulnerable to the stress of undergoing major surgery, resulting in increased morbidity, mortality and length of hospital stay.

Current programmes aim to improve postoperative outcomes by undertaking a multimodal prehabilitation approach. This may include optimisation of medical conditions, advice and support for undertaking physical activity, as well as specific nutritional support. All patients who smoke should be offered help and advice from smoking cessation services. In addition, some patients may benefit from individual or group psychological support.

This series of potentially modifiable risks may be incorporated into a personalised prehabilitation programme. For each of the areas, interventions may be universal, targeted or specialist.

• Universal interventions are all that will be required for many patients to optimise fitness and nutrition. This includes healthy eating and maintaining a reasonable level of physical activity, the guidelines for which can be preoperatively given to all patients.

• More targeted interventions may benefit some patients, such as referral for exercise programmes that have the appropriate support for patients with additional needs related to their diagnosis or comorbidities. For nutritional support, referral to a dietician may identify areas for improving food intake preoperatively.

• Specialist intervention may be required in some higher-risk patients in one of the domains mentioned. This may include a fully supervised exercise intervention or the addition of artificial nutritional support by enteral or intravenous nutrition.

It has now been shown that these interventions can have benefits for patients when started at any point in their preoperative pathway; in addition, they can provide a distraction for patients undergoing other treatments such as preoperative chemotherapy ( EBM 7.1 ).

Assessment of the patient for emergency surgery

The principles of assessment, investigation and preparation of patients for elective surgery apply equally to the emergency setting but may be curtailed by a lack of time and information. As a result, emergency surgery is often associated with increased morbidity and mortality compared with elective surgery. Emergency patients often require resuscitation prior to surgery; assessment and management of airway, breathing and circulation should be the first priority. Particular care should be taken to restore circulating volume wherever possible prior to surgery with the exception of life-threatening haemorrhage-penetrating trauma or where haemodynamic stability cannot be maintained. This is because anaesthesia is associated with attenuation of normal cardiovascular compensatory mechanisms, and significant hypotension can result.

Overzealous attempts to restore biochemistry, haematology and coagulation to normal at the expense of a marked delay in surgery are also to be avoided. This is particularly the case in the timing of surgery for sepsis, where the need for adequate surgical source control may outweigh small benefits associated with investigations or interventions that delay surgery (e.g., the correction of modest hyperglycaemia in the diabetic patient with peritonitis).

Preoperative risk scoring systems

Scoring systems to predict surgical risk for individual patients and for comparative audit are being used increasingly ( EBM 7.2 ). The most widely used preoperatively is the ASA score, a subjective assessment of a patient’s overall health and physical status ( Table 7.2 ). It correlates well with postoperative complications and death but has major limitations. The most established of the scoring systems is the Portsmouth Physiologic and Operative Severity Score for enumeration of Morbidity and Mortality (P-POSSUM). Eighteen variables (12 physiologic and 6 operative) are used to calculate the score to estimate predicted morbidity and mortality, making it complex to calculate. Some of the variables are also unknown until after surgery. Preoperative P-POSSUM has been used to predict risk of surgery, for example, in emergency laparotomy where a predicted mortality of more than 10% has been suggested as a trigger for admission to critical care. In the UK, the National Emergency Laparotomy Audit (NELA) has developed a risk calculation tool to provide an estimate of the risk of death within 30 days of emergency abdominal surgery. This tool has performed better than the P-POSSUM calculator but is specific for patients undergoing emergency laparotomy.

The National Surgical Quality Improvement Program (NSQIP) has also developed a surgical risk calculator that aims to provide a patient-specific risk to guide decision making. It uses 20 variables and the procedure code to predict the risk of death and 18 specific complications after surgery.

Although all these scores require imputation of multiple data points and complex calculations, web-based calculators or apps are able to provide clinicians with this information at the bedside or outpatient clinic ( Table 7.9 ).

Venous thromboembolism (VTE) prophylaxis

VTE accounts for thousands of deaths each year due to fatal PE and many are hospital acquired. Deep venous thrombosis (DVT) may also cause morbidity and chronic health problems including leg ulcers and decreased mobility. Prevention of VTE is therefore a cost-effective treatment of great benefit to patients.

All surgical patients should have their risk of VTE assessed prior to, or on, admission to hospital to enable prophylactic measures to be taken. Risk of bleeding or bleeding-related complications should also be assessed, and the type of surgery plus any other perioperative interventions, e.g., neuraxial blockade will need to be considered. The magnitude of the risk of DVT relates to patient and operative factors. All surgical patients should be assessed for the risk of thrombosis ( Table 7.10 ) and bleeding ( Table 7.11 ) and there are a number of risk calculators which take these factors into account when planning thromboprophylaxis. Any thrombosis risk should prompt thromboprophylaxis. Any bleeding risk should prompt an assessment of whether risk is sufficient to preclude use of pharmacologic prophylaxis.

Two options for thromboprophylaxis, mechanical and pharmacologic, are available ( Table 7.12 ). All surgical patients with increased risk of VTE should be offered mechanical VTE prophylaxis at admission and pharmacologic VTE prophylaxis if the risk of bleeding is low.

Mechanical thromboprophylaxis should be avoided in suspected or proven peripheral arterial disease, peripheral arterial bypass grafting, peripheral neuropathy and local conditions that antiembolism stockings may exacerbate, e.g., dermatitis, skin graft, known allergy, severe leg oedema or major limb deformity preventing correct fit.

Thromboprophylaxis should be continued until mobility is not significantly reduced, usually for 5 to 7 days, with the exception of orthopaedic lower limb surgery, where it should be continued for 2 to 4 weeks after surgery. General measures such as maintaining hydration and encouraging mobility should be taken to reduce risk. In patients at very high risk of VTE, the use of an inferior vena caval filter may be considered, but specialist advice should be sought. Women should consider stopping oestrogen-containing contraceptives and hormone replacement therapy (HRT) 4 weeks prior to surgery.

Preoperative medication

There are a number of indications for preoperative medications to be administered, and these may be given to patients either the night prior to or on the day of surgery. The use of preoperative anxiolytics is at the anaesthetist’s discretion; however, their use has declined with increasing numbers of day case procedures. The aim of administering a preoperative anxiolytic is for the patient to arrive in the anaesthetic room in a relaxed, pain-free state. This can often be achieved alone by reassurance and adequate explanation of the planned procedure, except in the very anxious patient. Oral benzodiazepines are commonly used as they have a relatively long duration of action, meaning accurate timing of administration with regard to anaesthetic induction is not required.

Anticholinergic medications such as glycopyrrolate may be administered preoperatively to reduce secretions in patients requiring fibreoptic intubation. In addition, medications may be given to reduce the volume and acidity of gastric contents prior to induction of anaesthesia.