Principalism

Principalism is a widely adopted approach to medical ethics. Championed by Beauchamp and Childress, it judges all possible actions in a particular ethical dilemma against four principles. These are autonomy, beneficence, non-malfeasance and justice (Summary Box 5.1). Each is considered in more detail below and while addressed separately, it becomes apparent that the principles are linked and do not simply cover four unrelated issues. Protagonists of this approach to bioethics suggest that it provides a practical framework for working through ethical dilemmas, allowing identification of important issues and is universally applicable with its four principles widely acceptable irrespective of culture or religious beliefs. The principles can be applied to most surgical clinical scenarios and if each element is given due consideration it is unlikely that the resulting decision will be unethical.

General considerations

Informed consent is central to the practice of surgery, and has to be obtained for surgical procedures, other treatment modalities, investigations, screening tests and prior to patient participation in research. Informed consent is not only ethically correct but also a legal riht and should be respected even if the patient’s wishes are at variance with the surgeon’s opinion. Informed consent can only be obtained from patients with ‘capacity’. This should be assumed for all conscious adults unless there is evidence to the contrary. The patient’s views must be respected and upheld after an information sharing process that conveys all the information the patient needs and wants in order to make a decision. The surgeon must maximize the opportunity for patients to consent and facilitate the process wherever possible.

Capacity exists if a patient can:

Circumstances where the capacity to consent may not exist:

Other important considerations in obtaining consent relate to who should obtain consent and when, and what information should be shared/withheld and in what format. In general terms, the surgeon performing the procedure has responsibility to obtain consent but this can be delegated provided the person to whom it is delegated:

The information that should be shared with a patient to obtain consent should start from a mutual understanding by both doctor and patient of the medical condition, as well as the patient’s views, beliefs and prior knowledge. All treatment options should be detailed, including the option of no treatment alongside the risks, side effects, potential benefits and burdens and the risk that the treatment will be unsuccessful. All potential serious adverse outcomes, no matter how rare should be discussed, along with more frequent minor complications. Risks and benefits should, wherever possible be quantified in percentage terms. These figures should derive from audited local/personal practice and not simply plucked from the literature. It is acceptable for the surgeon to give the patient advice; but, in such circumstance, any conflict of interest must be declared.

If a patient expresses the wish that they do not want the information required for informed consent and understands the potential consequences, then information can be withheld on the basis of non-malfeasance, but only when serious psychological harm might ensue and not simply because the patient may be upset or refuse treatment. This is called ‘therapeutic privilege’. The provision of procedure specific patient information sheets can supplement the process of informed consent, but does not negate the doctor’s responsibility to ensure patient’s understanding of the procedure.

Consent may be implied or explicit. Implied consent is considered adequate for routine interventions with negligible risks where patient consent is implied by their cooperation (e.g. venepuncture). The majority of interventions require explicit consent; this may be oral or written. It is perhaps surprising that although written consent is obtained for the majority of procedures, it is only a legal requirement for organ donation and fertility treatment in the UK. Nevertheless, the existence of a written, dated form of consent provides evidence that a consultation covering specific issues was likely to have taken place.

Increasingly in the UK patients may not have sufficient English to enable the process of informed consent. In such circumstances it is tempting to conduct the consultation and consent process via a family member or friend acting as an informal interpreter. However, best practice is to use the services of an official translator. Similarly, written information should in the appropriate language; if this is not possible the translator should read it out to the patient who then has an opportunity to ask questions back through the translator. It goes without saying that the medical records should clearly document that this process has taken place.

Consent in specific circumstances

Confidentiality

Confidentiality is a central element in the doctor–patient relationship. There are exceptions where confidentiality can and should be breached for the protection of others (e.g. notifiable diseases such as tuberculosis). In the context of multidisciplinary team working, only information necessary to enable treatment by a third party should be divulged. When patients are discussed for the purposes of teaching or publication, patient identity must be concealed. Confidentiality is not just an important principle, it may be legally enforceable, for example by the Data Protection Act.

See Table 5.2 for important sources of information regarding ethics in medicine.

Table 5.2 Sources of further information on ethics

Publications • Guidelines published by the General Medical Council (also available on-line) include: Good Medical Practice, 2006 0–18 years: guidance for all doctors, 2007 Consent: patients and doctors making decisions together, 2008 Confidentiality, 2009 Treatment and care towards the end of life, 2010 Good practice in research and consent to research, 2010 • Jonathan Herring. Medical Law and Ethics. 2nd edition, Oxford University Press, 2008 • Margaret Brazier and Emma Cave. Medicine, Patients and the Law. Penguin, 2007

Euthanasia and ‘end-of-life’ issues

Euthanasia is described as a deliberate intervention undertaken with the express intention of ending life, to relieve intractable suffering due to an incurable, progressive disease. It is usually requested by the patient and is illegal in the UK, as is assisted suicide.

Other ‘end-of-life’ issues such as withholding and withdrawing futile treatments or any treatments at the request of a competent patient are separate issues and should not be confused with euthanasia. Where treatment with ‘double effect’ is used, such as opiate analgesia (relieves pain and anxiety while shortening life), this is acceptable because the primary intention was to relive pain, distinguishing it from euthanasia.

Abortion

In the UK, legal abortion is permitted under the terms of the Abortion Act 1967; amended by the Human Fertilisation and Embryology Act 1990 that reduced the gestational age at which abortion could be carried out from 28 to 24 weeks. The conditions for performing abortion up to 24 weeks of gestation are that continuing the pregnancy would cause greater risk of injury to the mental or physical health of the woman, or any existing children of her family. Abortion can be carried out after the 24th week of pregnancy if it is necessary to save the mother’s life, if there is grave risk of permanent injury to the mental or physical health of the woman by continuing the pregnancy, or if there is substantial risk that the child would have severe physical or mental problems that would render them seriously handicapped. In all cases, two registered medical practitioners have to agree the criteria and appropriateness of the abortion. While a doctor has no obligation in UK law to be involved in abortion if he/she has a conscientious objection, they must refer the patient to a doctor who is. This conscientious objection does not extend to emergency situations where the life or health of the mother is endangered. Although surgeons are only infrequently involved in decisions around abortion, understanding the law is important, especially in the context of trauma or acute abdominal pain in the early stages of pregnancy.

Negligence

In order for a surgeon to be found negligent three pre-requisites must be fulfilled. Firstly, it must be demonstrated that the surgeon owed the patient a duty of care (this is usually assumed), secondly, it must be shown that that the doctor breached that duty of care; and, thirdly that, on the balance of probabilities (more likely than not), the breach of duty resulted directly in harm (causation). Medical negligence can relate to diagnosis, treatment and the failure to warn a patient of risks that would have resulted in the patient refusing an intervention. The standard against which a doctor’s performance is measured was established in case law in 1957 (the Bolam case). This states that a doctor is not guilty of negligence if he has acted ‘in accordance with a practice accepted as proper by a responsible body of medical men skilled in that particular area’. In practice, Bolam defends a doctor’s practice if a body of medical opinion can be found to support that doctor’s actions. It facilitates the defence of minimal acceptable practice rather than ideal practice. A subsequent House of Lords ruling went further stating that, ‘the court has to be satisfied that the exponents of the body of opinion relied on can demonstrate that such an opinion has a logical basis … that the experts have directed their minds to the question of risks and benefits and have reached a defensible conclusion’. This updated ruling (Bolitho) provides the legal basis for most complaints that result in an allegation of negligence. Several professional organizations in the UK offer advice and support to doctors including the British Medical Association, the General Medical Council, and medical defence organizations.

Human Tissue Act

The Human Tissue Act 2004 replaced the Human Tissue Act 1961, the Anatomy Act 1984 and the Human Organ Transplants Act 1989, in England and Wales. A similar act was passed in Scotland in 2006. This was in response to inadequacies in preceding legislation brought to light by inquiries into the storage of human tissue in the Alder Hey and Bristol inquiries. The Human Tissue Act places consent as the fundamental principle in the storage of human tissue, whether from living patients or the deceased and issues legislation and guidance regarding the removal, storage and use of human tissue.

Completion of a death certificate

Following the death of a patient, it is a legal requirement that a death certificate be completed before the body is released for cremation or burial. Death certification must be completed by the doctor who has attended the deceased during their last illness and includes a record of the patient’s name and age, as well as the date, time and place of death. The cause of death has to be recorded, as well as any contributing conditions that have led directly to the cause of death and significant conditions that contributed to the death but are unrelated to the disease causing it. In certain situations a death has to be referred as a legal requirement to the coroner’s office in England, Wales and Northern Ireland or to the Procurator Fiscal in Scotland for consideration of a post mortem examination to establish the cause of death. These include: recent surgery, where death may be due to abortion, accidental death, death in suspicious/violent/unnatural circumstances, death due to suspected poisoning, self neglect, negligence or suicide, death occurring in prison or police custody, where the death may be due to industrial disease or related to the deceased person’s employment, where the cause of death is unknown; and unexpected death.

Where cremation is requested, a separate cremation form has to be completed by a doctor who attended the deceased during their last illness and a second doctor who is at least five years full registration. Care must be taken to identify the presence of pacemakers and other potential explosive devices in the body. The cremation of foetal remains of less than 24 weeks gestation does not require a cremation certificate.

Post-mortem examination

A post mortem is carried out in two situations. There may be a legal requirement to establish the cause of death prior to a death certificate being issued as detailed above. This mandatory Coroners’ post mortem does not require the consent of the deceased person’s family. Alternatively, the deceased person’s next of kin, relatives or doctors may request a post mortem to provide information about the deceased’s illness or cause of death. In this instance consent from the next of kin should be obtained to proceed with post mortem examination and should include details of the possible outcomes of post mortem. The Human Tissue Act provides specific recommendations for the handling and storage of tissues and organs removed at post mortem. Further detail is beyond the scope of this chapter.

Research governance

Research governance serves to improve research quality and safeguard the public by enhancing ethical and scientific quality, promoting good practice, reducing adverse incidents and ensuring lessons are learned, and preventing poor performance and misconduct. All of this is be achieved through a broad range of regulations, principles and standards of good practice, originally enshrined in the Declaration of Helsinki in 1964 (for more information see version 6, released in 2008). Research governance applies to everyone involved in medical research whether as chief investigator, care professional, researcher, the employing institution or sponsor. This governance safeguards participants, protects researchers and investigators, minimizes risk, and enables the monitoring of practice and performance. Surgical journals place great emphasis on research governance. Work that does not demonstrate adherence to satisfactory ethical and quality standards is likely to be rejected.

Ethics committees

Research on human subjects is necessary to advance medical knowledge and treatment. Ensuring that it is carried out in a safe and ethical way is the remit of the ethics committee. The Declaration of Helsinki sets out the principles of ethical research. All clinical trials involving human subjects or tissue must receive ethical approval prior to commencing recruitment. For information on how ethical approval is obtained in the UK see the National Research Ethics Service which is part of the National Patient Safety Agency (http://www.nres.npsa.nhs.uk/). The composition of ethics committees is important and should reflect societal diversity in terms of age, gender, ethnicity and disability and embody a broad range of experience and expertise so that the scientific, clinical and methodological aspects of a research proposal can be reconciled with the welfare of the research participants.

Ethics committees take into consideration a whole range of aspects of a research proposal before giving approval. Their primary consideration is to safeguard the rights, safety and wellbeing of research subjects. They examine the recruitment process, including informed consent, the quality of information given to subjects, payments to subjects, the risks of the research protocol including safety measures and information, compensation procedures and indemnity. The likelihood and capability of the trial design to answer the research questions is considered as well as adequacy of resources, plans for data processing, storage and protection.

Oxygen delivery in minimizing operative risk

A number of important studies have demonstrated that postoperative morbidity and mortality are related to inadequate oxygen delivery to the tissues, resulting in hypoxia. Oxygen delivery (DO₂) is dependent on cardiac output (CO) and the oxygen content of arterial blood (CaO₂).

The arterial oxygen content in turn depends on the delivery of oxygen to the alveoli, its efficient transfer from alveoli into blood, adequately functioning haemoglobin, the arterial partial pressure of oxygen and arterial haemoglobin oxygen saturation. In an average resting adult an oxygen requirement of approximately 250 ml/min is exceeded by delivery of around 1000 ml/min, resulting in considerable reserve. When oxygen demand increases, cardiac output may rise and tissue oxygen extraction may increase to up to 50–60% in order to compensate. If this does not meet tissue oxygen demand, hypoxia with anaerobic metabolism ensues. If uncorrected this can cause local and remote organ damage, dysfunction, multiple organ failure and ultimately death. It has been shown that the duration of oxygen debt correlates with the presence and magnitude of postoperative complications and mortality. It therefore follows that patients with poor cardiovascular and respiratory reserve or anaemia, and who are less able to increase oxygen delivery, are at higher perioperative risk and that measures taken to optimize their condition and oxygen delivery will help to minimize that risk.

Goal directed measures to optimize cardiac index, oxygen delivery, mixed venous oxygen saturation and minimize anaerobic metabolism using intraoesophageal Doppler probes, pulmonary artery catheters, intravenous fluid loading, blood transfusion, supplemental oxygen and inotropes have all been shown to improve outcomes.

Cardiovascular system

The severity of cardiovascular disease is assessed and signs of undiagnosed or inadequately treated disease sought. Angina and previous myocardial infarction indicate significant coronary artery disease although bypass grafting, angioplasty and coronary artery stenting may ameliorate their associated risks. Exertional dyspnoea, orthopnoea and paroxysmal nocturnal dyspnoea may indicate left ventricular failure, whilst significant dependent oedema could signify right sided heart failure. The drug history is important and may alert to the presence and severity of cardiovascular disease. Blackouts and dizzy spells may be a sign of arrhythmias, carotid artery or valvular heart disease. Clinical examination should detect arrhythmias, carotid artery, heart murmurs, hypertension and signs of cardiac failure. Antiplatelet agents and anticoagulants are widely prescribed in the general population and may need to be stopped or modified prior to surgery (see below).

Respiratory system

A history of new or increased cough, sputum production, and shortness of breath or wheeze may indicate unsuspected respiratory disease or an exacerbation of pre-existing pulmonary disease. In patients with asthma, chronic obstructive pulmonary disease (COPD) or fibrotic lung disease, purulent sputum may indicate an infective exacerbation. In asthmatics, previous ITU and hospital admissions as well as steroid dependency indicate severe disease. Functional respiratory reserve is best assessed by exercise tolerance, for example how far a patient can walk on the flat, up an incline, or how many stairs they can climb before needing to rest because of shortness of breath. Significant dyspnoea should be investigated with pulmonary function tests.

Patients with features of acute viral respiratory illness should have surgery postponed where possible. This is due to the increased risk of bronchospasm and susceptibility of the respiratory epithelium to postoperative bacterial pneumonia which is compounded by the effect of general anaesthesia which depresses ciliary activity, reducing the clearance of secretions and pathogens.

Smoking

All patients should be offered support to quit smoking, particularly once the decision to operate has been made. The benefits of preoperative smoking cessation are listed in Table 5.3 and should be explained to the patient. Some of the benefits occur within hours (reduced circulating nicotine and carboxyhaemoglobin) while others take weeks, months, or even years. Despite the significant advantages in the perioperative period, many patients are unable or unwilling to stop smoking prior to and after their surgery. Referral to specialist services that support patients to stop smoking may help.

Table 5.3 Benefits of preoperative smoking cessation

Preoperative exercise

Interest in preoperative exercise has resulted from surgical enhanced recovery programs which aim to reduce the length of hospital stay following surgery and expedite return to normal activity. In addition, it has been hypothesized that preoperative exercise may reduce perioperative morbidity by improving cardio-respiratory performance. Some early studies investigating preoperative exercise programs, particularly in the field of orthopaedic surgery showed improved preoperative functional status and muscle strength which resulted in reduced inpatient rehabilitation requirements. However, results have been conflicting and this remains an active area of research.

Alcohol

It is important to obtain an accurate history as significant alcohol consumption can impact surgical planning. In chronic alcohol abuse, liver enzymes are induced, increasing hepatic drug metabolism. Consequently, increased doses of hepatically metabolized drugs, including anaesthetic agents are required to achieve therapeutic effect. Conversely, in acute alcohol intoxication reduced anaesthetic doses are required. In addition, the risk of aspiration pneumonia should be anticipated and preventive measures taken. The risk of alcohol withdrawal should also be anticipated and prevented in habitual alcohol consumers with use of detoxification protocols. In patients with a significant alcohol history, the risk of alcohol related liver and cardiac disease and coagulopathy should be anticipated.

Nutritional status

All patients should have their height and weight measured and BMI (body mass index) calculated. A history of weight loss should be sought and quantified as a percentage of the patients starting weight. It is important to look for signs of malnutrition such as low BMI, bodyweight < 90% predicted, > 20% weight loss, hypoproteinaemia and hypoalbuminaemia as they have all been related to increased rates of postoperative complications (particularly infective and pulmonary) as well as delayed anastamotic and wound healing. Pre-existing hypoalbuminaemia compounded by perioperative fasting and haemodilution results in oedema which may delay recovery. For these reasons, it is important to treat malnutrition preoperatively if time permits. The use of nutritional support should be considered in conjunction with dieticians.

Obesity

Obese patients are at increased risk from surgery and anaesthesia and special equipment may be required. Obese patients are at risk of major associated co-morbidities (e.g. diabetes, obstructive sleep apnoea, degenerative joint disease and cardiovascular disease). Table 5.4 details some of the technical difficulties, perioperative risks and comorbid conditions associated with obesity. If the risks of surgery are outweighed by its potential benefits, surgery may be postponed. In practice, the majority of patients cannot lose weight without support and referral to the GP and dietician for weight loss programmes, including supervised exercise, may be beneficial.

Table 5.4 Significance of obesity in the perioperative period

Full blood count

The majority of patients undergoing surgery will have a preoperative full blood count. The oxygen carrying capacity of blood (haemoglobin concentration) is of paramount

importance but the platelet and white cell count are also important considerations in terms of haemostatic capacity and where sepsis is suspected. Any patients undergoing surgery with the potential for significant blood loss should have a full blood count, as should those with signs or symptoms of anaemia, patients with significant cardiorespiratory disease that may compromise oxygen delivery to the tissues and those with overt or suspected blood loss (for example gastrointestinal tract symptoms).

Wherever possible, anaemia should be corrected preoperatively to optimize oxygen delivery to the tissues. Preoperative blood transfusion should only be considered for haemoglobin concentrations below 8 g/dl unless the patient is at increased risk of tissue hypoxia due to significant cardiorespiratory disease, especially severe ischaemic heart disease or severe intraoperative bleeding (EBM 5.1). (http://www.transfusionguidelines.org.uk) The threshold for transfusion should be higher (because lower haemoglobin concentrations are tolerated) in patients with chronic anaemia (such as renal failure patients) where compensatory mechanisms such as increased red blood cell 2,3-diphosphoglycerol and reduced blood viscosity increase oxygen delivery.

An abnormally elevated white cell count may indicate infection or haematological disease and should be investigated preoperatively. Thrombocythaemia increases the risk of thromboembolism and prophylactic measures should be taken. Thrombocytopenia may need to be corrected to reduce the risk of bleeding. The UK blood transfusion service recommends transfusing to a platelet count of 50 × 10⁹/l for lumbar puncture, epidural anaesthesia, endoscopy with biopsies and surgery in non-critical sites and to 100 × 10⁹/l for more major surgery including critical sites such as neurosurgery or ophthalmic surgery. Advice from a haematologist may be helpful.

Coagulation screen

The indications for coagulation studies are shown in Table 5.6 and include suspected abnormal clotting, anti-coagulation treatment and consideration of epidural anaesthesia. When disseminated intravascular coagulation (DIC) is suspected, such as in sepsis, fibrinogen, fibrinogen degradation products (FDP) and D-dimers should be measured. The surgical implications of selected disorders of coagulation are considered below.

Table 5.6 Indications for preoperative coagulation studies

Ischaemic heart disease

Ischaemic heart disease is common; increases with age; and significant number of patients with significant coronary artery disease are asymptomatic. Preoperative assessment therefore should focus not only on documented ischaemic heart disease but also on the diagnosis and investigation of occult or undiagnosed disease, especially in high-risk groups (Table 5.13).

Table 5.13 Factors indicating increased risk of ischaemic heart disease

Congestive cardiac failure

The commonest cause of congestive cardiac failure is ischaemic heart disease but the exact cause should be determined where possible as it may influence treatment. Cardiac failure is associated with a number of complications as a result of either poor pump function or underlying cardiac disease (Table 5.15). Uncontrolled heart failure indicated by peripheral oedema, paroxysmal nocturnal dyspnoea or orthopnoea is associated with very high perioperative risk and should be controlled prior to elective surgery.

Table 5.15 Increased perioperative risk in patients with cardiac failure.

Valvular heart disease

The severity of valvular heart disease should be assessed by clinical evaluation and echocardiography. Associated arrhythmias and cardiac failure should be excluded. An algorithm for the preoperative work-up of these patients in shown in Figure 5.3. Antibiotic prophylaxis guided by local protocol will depend on the risk of bacterial endocarditis according to the surgical procedure and the presence and type (metallic or bioprosthesis) of prosthetic heart valve.

Fig. 5.3 An algorithm for managing patients with known or suspected valvular heart disease.

Pacemakers

Pacemaker function may be affected by anaesthetic equipment and diathermy. It is important to establish the indication for pacemaker insertion, the date of insertion and last check, as well as the pacemaker type prior to surgery. Advice from the pacemaker clinic may need to be sought. Referral may be necessary for preoperative device reprogramming or a check if more than three months have elapsed since the last check. Monopolar diathermy should be avoided. Bipolar diathermy or ultrasonic energy devices are preferred. If monopolar diathermy cannot be avoided, care should be taken when placing the patient return electrode to direct the electrical current away from the pacemaker.

Hypertension

Uncontrolled hypertension increases the risk of perioperative myocardial infarction and cerebrovascular accident. A diagnosis of hypertension requires repeated, accurate blood pressure measurements which should be interpreted with respect to the patient’s age. An elevated diastolic pressure is of greater significance than the systolic pressure, contributing most of the excess risk. Organ blood flow is tightly regulated over a range of blood pressures; in hypertensive patients, this range is elevated rendering them vulnerable to organ hypoperfusion even with modest intra-operative hypotension during anaesthesia.

Hypertension should be controlled in the elective setting for a few weeks prior to surgery. This is to enable the autoregulatory mechanisms that control organ blood flow to reset and maintain organ perfusion at the lower blood pressure, a process that takes several days. Elective surgery should usually be postponed when the diastolic pressure exceeds 110 mmHg. In the emergency situation a modest reduction in blood pressure to minimize cardiovascular risk whilst maintaining adequate organ perfusion can be achieved intraoperatively by careful titration of antihypertensives. Regional anaesthetic techniques offer an alternative approach in the emergency setting, by avoiding the potentially large swings in blood pressure associated with general anaesthesia that may cause dysregulation of organ perfusion.

Perioperative management of patients with cardiovascular disease

Anaesthetic technique

General anaesthesia is associated with a risk of respiratory complications in part due to altered respiratory function caused by general anaesthesia. This is of particular concern in patients with pre-existing respiratory disease and reduced respiratory reserve. Where possible, general anaesthesia should be avoided through the use of regional anaesthetic techniques in this patient group.

Postoperative analgesia

Effective postoperative analgesia is important to maintain adequate cough, sputum clearance and ventilation, particularly in patients who have undergone thoracic and major abdominal surgery in order to avoid atelectasis, chest infection and hypoxia. Regional anaesthetic techniques, including spinal and epidural analgesia are effective in this regard. Parenteral opiates are effective analgesics but care should be taken not to cause respiratory depression or obtund the conscious level.

Physiotherapy

Pre- and postoperative chest physiotherapy is particularly important in patients with respiratory disease. Manoeuvres that facilitate maximal inspiratory effort and the use of incentive spirometry are particularly useful in minimizing the risk of atelectasis and guarding against hypoxia and pneumonia.

Postoperative ventilation

Postoperative ventilation may be indicated for respiratory failure as a result of insufficient respiratory reserve or complications such as pneumonia. Meticulous attention to analgesia and regular chest physiotherapy may avoid the need for ventilation. The duration of endotracheal intubation should be minimized because it also increases the risk of pneumonia. The use of non-invasive respiratory support with either non-invasive ventilation (NIV) or continuous positive airway pressure (CPAP) via a face mask may avoid the need for ventilation and be a useful bridge whilst weaning a patient from ventilatory support.

Diabetic comorbidity

Effect of surgical stress on diabetic control

Part of the metabolic response to surgery involves glucose mobilization and lipolysis with increased circulating insulin levels to maintain homeostasis and normoglycaemia. The net result in diabetics is a tendency towards hyperglycaemia and ketoacidosis following surgery, which is exaggerated if complications such as sepsis develop. Glycaemic control should be monitored closely and insulin or oral hypoglycaemic drug doses titrated accordingly. The metabolic response to surgery is discussed in more detail in chapter 1.

Principles of perioperative diabetes management

The aim of perioperative diabetic management is to maintain stable circulating glucose levels, ensuring an adequate supply to the cells. A circulating glucose concentration of 6–10 mmol/l is a reasonable target range. As hypoglycaemia is more dangerous to the patient than hyperglycaemia, moderate hyperglycaemia is acceptable. Care should be taken to administer sufficient potassium when insulin is administered as insulin increases cellular potassium uptake, with a tendency towards hypokalaemia. The approach used to achieve perioperative glycaemic control depends on a number of factors including:

In practice, many units have protocols for the perioperative management of diabetes, which can be tailored to the individual patient. Table 5.17 gives examples of the typical approach to diabetic control.

Table 5.17 Typical scenarios for diabetic patients presenting for surgery.

Methods of insulin administration

For patients with poor glycaemic control or not established on their usual diabetic medication because normal dietary intake has not been established, sliding scale insulin is normally administered. Sliding scale insulin regimens consist of intravenous insulin, glucose and potassium that can be given as a single mixed infusion (the Alberti regimen) (Table 5.18) or as separate infusions of insulin and glucose with potassium. Single mixed infusions are simple, cheap and safer, with less risk of hypoglycaemia, but at the expense of greater flexibility and tight glycaemic control that can be achieved with separate insulin and glucose infusions.

Table 5.18 The Alberti Regimen

Spinal anaesthesia

Spinal anaesthetic is defined by the introduction of local anaesthetic, usually lidocaine or bupivacaine into the subarachnoid space to block the spinal nerves before they exit the intervertebral foramina (Fig. 5.4). To protect against damage to the spinal cord, spinal anaesthesia is administered below L2, either at the L3/4 or L4/5 level. At this level, the cauda equina nerves acquire their perineural coverings and myelin sheath as they exit the dura making them exquisitely sensitive to the effect of local anaesthetic. As a result, 2–4 ml of local anaesthetic produces a dense block up to T6 level, with a rapid onset of action, giving 2–3 hours of surgical anaesthesia. The addition of 6–8% glucose increases the density of the spinal anaesthetic solution making it easier to control the level of the block using gravity. Aspiration of subarachnoid fluid confirms the correct site of the spinal needle.

Fig. 5.4 Spinal anaesthesia.

A Position of the patient. B The anatomy of the lumbar spine and position of the needle in the subarachnoid space as for spinal anaesthesia.

Epidural anaesthesia

Both spinal and epidural anaesthesia block spinal cord sympathetic outflow. Rapid vasomotor paralysis with peripheral vasodilatation is an early sign of a successful spinal or epidural anaesthetic due to the rapid onset of blockade in these small unmyelinated fibres. Conversely, the resulting peripheral vasodilatation can be a nuisance with unwanted hypotension requiring treatment with intravenous fluids, vasoconstrictors, or reduction in the rate of the epidural infusion.

Epidural anaesthesia involves the injection of local anaesthetic into the epidural space which extends along the entire vertebral canal between the ligamentum flavum and dura mater (Fig. 5.5). Local anaesthetic spreads cranio-caudally penetrating the meningeal sheaths containing the nerve roots causing an anaesthetic block affecting several dermatomes. The level of epidural anaesthetic is therefore dictated by the proposed site of surgery and the dematomes involved. The nerve roots are fully covered and myelinated as they traverse the epidural space and therefore a larger volume (10–20 ml) of local anaesthetic, compared to spinal anaesthesia, is required to achieve anaesthesia. The technique by which a needle is introduced into the epidural space depends on sensing a loss of resistance as the needle passes through the ligamentum flavum; aspiration ensures that the needle is not advanced too far into the subarachnoid space, termed a ‘dural tap’. An ongoing CSF leak following a dural tap can lead to loss of CSF volume and headache. As well as adequate hydration, the CSF leak may be managed by the use of a blood patch. This involves using the patient’s own blood injected into the epidural space to seal the leak. If a dural tap goes undetected with the injection of local anaesthetic into the subarachnoid space, a profound block of all spinal nerves will result, with the potential of respiratory arrest and profound hypotension. A catheter is often left in the epidural space to provide access for ongoing analgesia. Table 5.24 details some common complications of epidural anaesthesia. Both spinal and epidural anaesthesia block spinal cord sympathetic outflow. Rapid vasomotor paralysis with peripheral vasodilatation is an early sign of a successful spinal or epidural anaesthetic due to the rapid onset of blockade in these small unmyelinated fibres. Conversely, the resulting peripheral vasodilatation can be a nuisance with unwanted hypotension requiring treatment with intravenous fluids, vasoconstrictors, or reduction in the rate of the epidural infusion.

Fig. 5.5 Epidural anaesthesia.

Table 5.24 Complications of epidural anaesthesia and analgesia

Epidural analgesia

Epidural analgesia is commonly achieved by a continuous infusion of local anaesthetic, usually in combination with an opiate, into the epidural space. A typical regimen of 0.1% bupivacaine with 2 mg/ml fentanyl running at a rate of up to 16 ml/hour is used for thoracic, abdominal and major lower limb surgery. Inserted prior to surgery, an epidural catheter can safely remain in place for up to five days. Pain relief is superior to parenteral opiates but careful patient monitoring in an appropriate environment by trained staff is needed. There is a rate of epidural failure due to misplacement, displacement, inadequate analgesia or intolerable side effects which should be managed with timely epidural replacement or substitution with another analgesic technique. In addition to the complications discussed above as per epidural anaesthesia, permanent neurological damage (0.005–0.05%) is a devastating but rare complication. Respiratory depression due to cephalad spread of opiates may also occur.

Patient-controlled analgesia (PCA)

Patient controlled analgesia (PCA) involves the use of a pre-programmed pump to deliver a small, pre-determined dose of drug, usually an opiate, with a minimum time period between doses (lock-out period). The lock-out period allows the patient to feel the effect of the opiate bolus before administering a subsequent dose, minimizing the amount of opiate consumed and the risk of respiratory depression which occurs in up to 11.5% of patients. A typical regimen would involve 1 mg morphine at 5-minute intervals, although this may vary according to patient size, age and history of opiate exposure. Background opiate infusions are not routine due to the increased risk of respiratory depression but may be useful in chronic opioid users. Similar to epidurals, PCA requires expensive pumps and to be successful, the patient must understand how it works and have the manual dexterity to use the pump. Care must be taken in correct pump programming and in delivering the correct concentration of opiates as deaths from respiratory depression have been reported.

Parenteral and oral opioid regimens

Paracetamol, NSAIDs and selective Cox-2 inhibitors

Paracetamol is effective in the management of post- operative pain and can be administered by the oral, intravenous and rectal routes. Regular use has been shown to reduce opioid requirements by 20–30% and in combination with NSAIDs, the combination is more effective than NSAIDs alone. Paracetamol should therefore be prescribed to all postoperative patients except in the rare instance of contraindications.

NSAIDs are also an important component of multimodal postoperative analgesia. In combination with opioids, NSAIDs increase analgesia and have an opioid sparing effect, reducing consumption, postoperative nausea and vomiting and sedation. Their use is limited by their side effect profile, including renal impairment, impaired platelet function with the potential for increased postoperative bleeding, peptic ulceration and bronchospasm in individuals at risk. Asthma is not an absolute contraindication and previous use without adverse effects permits their use.

Selective cyclo-oxygenase (COX)-2 inhibitors such as celecoxib, parecoxib and etoricoxib are as effective as NSAIDs in the management of postoperative pain and have an opioid sparing effect. Their potential advantage is an improved side effect profile compared with NSAIDs, with no impairment of platelet function, reduced gastrointestinal complications and no associated bronchospasm. The use of COX-2 inhibitors is limited by their association with a small increased risk of thrombotic events (myocardial infarction and stroke) and therefore they should not be used except where NSAIDs are contraindicated and after assessing cardiovascular risk. COX-2 inhibitors are contraindicated in ischaemic heart disease, cerebrovascular and peripheral arterial disease and moderate to severe cardiac failure. They should also be used with caution in patients with risk factors for these conditions.

Neuropathic pain

Acute neuropathic pain in the postoperative period occurs in at least 1–3% of patients and is probably underestimated. It is a risk factor for chronic neuropathic pain which may be reduced by early intervention. Expert advice should be sought to advise on the management as neuropathic pain does not respond well to conventional analgesia regimes. Because it does not respond well to conventional analgesic regimes expert advice should be sought. There is evidence that intravenous lidocaine infusions and gabapentin reduce pain and reduce opioid requirements. Tricyclic antidepressants are also used on the basis that they are effective in chronic neuropathic pain although their efficacy in reducing acute neuropathic pain has not been proven.

Postoperative nausea and vomiting

Postoperative nausea and vomiting (PONV) is common affecting 20–30% of patients for whom it is very distressing. It is also a significant factor in causing delayed discharge from day case surgical units. Certain risk factors for PONV have been identified, these include female sex, type of surgery (e.g. gynaecological and laparoscopic surgery), being a non-smoker, a history of previous PONV or motion sickness and opioid use. Anaesthetic technique is also important as, inhalational anaesthetic agents, especially nitrous oxide are associated with PONV whereas intravenous anaesthesia with propofol has a lower incidence. Management of PONV centres on identifying high risk patients and instituting preventative measures. Ondansetron and dexamethasone are particularly effective in the prophylaxis and treatment of PONV.