Julian Smith, Ming Kon Yii
10.1 Introduction
The most common chronic medical problems in surgical patients are hypertension, ischaemic heart disease, chronic obstructive airways disease, diabetes mellitus and alcoholic liver disease. Other disorders encountered include chronic renal injury, anaemia, cerebral vascular disease and disorders of haemostasis. Many patients have multiple medical conditions, particularly when there is a history of smoking and excessive consumption of alcohol. Many patients have associated depression or anxiety. Thus, when assessing any patient with a surgical problem, an adequate general history and physical examination is essential. Identifying associated medical problems at the first interview gives the best chance for them to be controlled prior to operation.
The aim of management is to make the patient as fit as possible for surgery within the timeframe allowed by the urgency of the surgical condition. Control of concurrent illness will markedly reduce surgical morbidity and mortality. For a patient with chronic bronchitis, stopping smoking several weeks before surgery and a course of chest physiotherapy can turn a procedure from one that is hazardous into one of almost complete safety.
When urgent surgery is required, correction of medical problems must be accelerated and should not delay imperative surgery, especially when the pathology is complicated by haemorrhage, inflammatory or ischaemic necrosis, or septicaemia. The patient’s condition must be improved as rapidly as possible for the forthcoming surgery; cardiovascular and respiratory support has maximum priority. A balance must be struck between the adequacy of resuscitation and the presence of a surgical emergency requiring prompt treatment. Unduly delaying surgery will inevitably lead to multisystem organ failure (MOF). In such patients, early surgery is an integral part of resuscitation and support of associated medical illness.
Assessment of individual systems is considered in detail in subsequent sections. Irreversible system failure may be an indication for organ or tissue transplantation, particularly when only one system is affected.
10.2 Assessing patients for surgery
Progress in anaesthetic and surgical practice has enabled more and more patients, over wider extremes of age, with more and more complex systemic diseases, to be treated by major surgery. Making the patient safe for surgery (Box 10.1) starts with detecting concurrent medical illness in the systems review and physical examination. Evaluation and subsequent treatment of major risk factors are important steps in the reduction of surgical mortality and morbidity. Surgical risk is the probability of mortality or complications associated with surgery or anaesthesia. Risk factors can be related to the procedure or to the patient or both.
Box 10.1
A safe system of surgery
Careful preoperative assessment and preparation
Correct timing of surgery
Correct choice of operation and anaesthetic
Correct patient and correct site and side of surgery
Staging surgical procedures, when necessary, to minimise risks
Intensive perioperative care and monitoring
Patient-related risk factors to be aware of include:
• the nature and severity of the surgical disease itself and the presence of complications
• associated systemic illnesses (cardiovascular, pulmonary, hepatic, renal, haematological, nutritional or metabolic problems)
• the patient’s age and general status.
Procedure-related risk factors may be anaesthesia-related or operation-related and vary with:
• the skill and experience of anaesthetist and surgeon
• the type of anaesthesia
• the type of operation and whether elective or emergency
• the facilities for perioperative monitoring and care.
The decision to perform surgery depends on weighing the risk factors contributing to mortality and complications against the prospective benefits of surgery in terms of curing disease or alleviating symptoms. In individual patients, other aspects such as relative costs of treatment are not usually considered, but ultimately the costs of surgery compared to its benefits will contribute to determining community expectations and acceptance of surgical procedures.
Of perioperative deaths, about one tenth occur during induction of anaesthesia prior to surgery itself; about one-third occur during operation; the remaining and majority of deaths occur within 48 hours of operation. The most common causes of deaths are cardiac (myocardial infarction and heart failure), pulmonary (pulmonary infections and embolus) and sepsis.
Grading of surgical and anaesthetic risk
Patients can be graded into five classes according to the severity of associated systemic diseases and of the surgical condition, as recommended by the American Society of Anaesthesiologists (ASA classification — Table 10.1). The suffix E is added to each class for those having emergency operations.
Table 10.1 ASA classification of anaesthetic risk
|
Class 1 |
Normal healthy patients for age |
|
Class 2 |
Mild systemic disease |
|
Class 3 |
More severe compensated systemic disease that limits activity but is not incapacitating |
|
Class 4 |
Uncompensated incapacitating systemic disease — a constant threat to life |
|
Class 5 |
Moribund — not expected to survive 24 hours with or without operation |
Emergency — precede the number with an E
Such a grading is associated with a progressive increase in anaesthesia-related and operation-related mortality as one proceeds from class 1 (a normal healthy patient) to class 5 (a patient unlikely to survive 24 hours with or without surgery). Patients in classes 1–3 are usually appropriate for consideration for elective surgery. Mortality of emergency operations is double that of elective operation in classes 1–3 but only marginally increased over elective operation in classes 4 and 5.
Evaluation of the healthy patient
Patients with no clinically detectable systemic illnesses except their surgical problem are classified into ASA class 1. Mortality for low-risk surgical procedures in this group is very low and complications are likely to be due to technical errors. The mortality for major high-risk surgical procedures in such patients is also low, of the order of a few per cent.
All such patients require a careful systems review by history and physical examination prior to operation. Preoperative special tests may be added in order to detect any subclinical disease that may adversely affect surgery and to provide baseline values for comparison in the event of postoperative complication. These tests should be sufficiently sensitive to detect an abnormality, yet specific enough to avoid the chances of over-diagnosis. The prevalence of the disease or condition being looked for is likely to be low in a healthy asymptomatic patient population. Thus most tests are likely to be within the normal range. The more tests that are done increases the likelihood of a false positive result due to chance. With extensive multiphasic screening profiles of healthy individuals, about 5% of healthy normal people will show one abnormal result.
Evaluation of the elderly asymptomatic patient
Ageing increases the likelihood of asymptomatic systemic illness and screening tests are therefore more stringently applied to older, apparently healthy patients. Elderly patients (aged over 70 years) have increased mortality and complication rates for surgical procedures compared with young patients. Problems are: reduced functional reserves; coexisting cardiac and pulmonary disease; renal dysfunction; poor tolerance of blood loss and greater sensitivity to analgesics; sedatives; and anaesthetic agents.
Complications of atelectasis, myocardial infarction, arrhythmias and heart failure, pulmonary emboli, infection and nutritional and metabolic disorders are all more frequent. Separation of the effects of ageing and of associated diseases is difficult. Most of the increased mortality and morbidity is due to associated disease.
Even greater care in assessment of cardiac, respiratory, renal and hepatic function before operation is therefore necessary for elderly patients.
Investigations and diagnostic (screening) tests before surgery
Urinalysis
Urinalysis should be routine for all patients. ‘User-friendly’ dipsticks have virtually eliminated observer variation and error. The various biochemical urine tests — glucose, bile, protein, reaction — are both sensitive and specific. Screening for glycosuria is particularly important, as subclinical diabetes can be precipitated into a diabetic state by operation or anaesthesia and septic risks are also increased. Urinary protein detection is relatively nonspecific but may alert the clinician to subclinical infection or renal disease.
Temperature
This test is a paradigm of one that is cheap and accurate, with only a small degree of observer error. It is very sensitive and very nonspecific. It should be and is, universally applied. Body temperature is an admirable monitor of the patient’s general postoperative progress. A raised temperature prior to operation will occasionally alert surgeon and anaesthetist to an upper respiratory tract infection prejudicing elective surgery.
Full blood examination
In asymptomatic patients, the incidence of anaemia will be low (<5%). A haemoglobin level of 10 g/dL is considered the lower limit of safety for most elective surgical operations. Oxygen transport will be impaired with haemoglobin levels <8 g/dL. Anaemia may not be clinically detectable until haemoglobin levels are less than 8 g/dL.
Blood typing
A case can be made for typing of all patients for ABO and Rh blood groups as baseline information prior to surgery but in practice only those patients undergoing moderate to large surgeries carrying a significant risk of intra-operative or postoperative haemorrhage require blood grouping.
Chest X-ray
Other than in populations with a high incidence of tuberculosis, chest X-ray has been found to be less sensitive than clinical history and physical examination. Routine chest X-ray is thus advised only in patients over 45 years.
Electrocardiogram
In asymptomatic healthy patients ECG will also have a low yield and is also indicated only in patients aged over 60 years unless there is a smoking history or the presence of other risk factors for cardiovascular disease.
Preoperative blood transfusion planning
The ready availability and safety of the blood banking system are two major factors in diminishing surgical risk. Public awareness of HIV/AIDS has reawakened interest in autologous blood collection and transfusion. Autologous transfusion is safe and can eliminate most of the risks and hazards of transfusion.
Therefore if blood replacement is likely to be required for elective surgery and requirements could be met by two units of autologous blood, the option of autologous transfusion should be considered. Usually two units are collected in the two weeks before operation. Certain operations (abdominal hysterectomy, elective joint prostheses and plastic surgical reconstructive operations) are particularly suitable.
The majority of patients having elective surgery where blood loss of less than two units (or <20% blood volume) is expected will merely need to have ABO and Rh grouping done and blood screened for irregular antibiotics (‘group and hold’ or ‘type and screen’). If loss is expected to be over two units, the appropriate amount of blood is cross-matched and reserved prior to operation. Consideration should also be given to the use of intra-operative red cell scavenging with a cell saver.
Other tests
In patients aged over 60 years serum glucose, renal function tests and tests of haemostatic disorders — prothrombin time (PT) and activated partial thromboplastin time (APTT), as well as any history of anticoagulant or antiplatelet agent ingestion — should be added (Box 10.2). Preoperative routine tests in those aged over 60 years should include ECG, chest X-ray, liver function tests, renal function tests, prothrombin time, APTT, platelet count and full blood count.
Box 10.2
Assessment for surgery: preoperative requirements and tests
All patients
Systems review by clinical history and examination; urinalysis. Note history of previous surgery, bleeding tendency, aspirin or anticoagulant medication or previous transfusion.
Young, healthy patients (<60 years), class I surgical risk
Blood type and screen for major surgery
Consider autologous transfusion
Full blood examination
Healthy patients 60–70 years, class I surgical risk
Blood type and screen (cross-match and reserve blood if expected loss >2 units)
Full blood examination
Chest X-ray
ECG
Serum glucose, creatinine, urea, electrolytes Na K Ca Cl
Coagulation profile
Liver function tests
Elderly patients >70 years
As for those under 70 years, plus:
lung function tests if respiratory symptoms
arterial blood gases if respiratory symptoms
noninvasive and perhaps invasive cardiac investigations for major surgery.
Other preoperative requirements relevant to all patients are preoperative chest physiotherapy assessment and education, preferably stopping smoking at least two weeks prior to operation, and assessment and correction of fluid and nutritional deficits.
10.3 Cardiac disease
Using noninvasive methods, Goldman,1 in the USA, proposed a concise system using nine identified risk factors for estimating the perioperative cardiac risk index (Box 10.3). Patient-related risk factors are: age over 70 years, previous myocardial infarction, heart failure, arrhythmias, ECG abnormalities, aortic stenosis and associated general medical illness. Procedure-related risk factors include intrathoracic, intraperitoneal and aortic surgery and emergency operations. Points are assigned for risk factors and patients are divided into classes with ascending scores. Mortality and morbidity rise steeply and progressively from class 1 to 4.
Box 10.3
Cardiac risk index: high risk factors
Age >70 years
Myocardial infarction <6 months ago
Heart failure
Aortic stenosis
Arrhythmia on ECG
Preoperative ectopic beats
General medical status
Blood gas abnormalities
Poor renal function
Poor liver function
Operation within chest or peritoneum or on aorta
Emergency operation
Major surgery increases oxygen demand and to meet this demand, patients need to increase cardiac output and ventilation. Elderly patients requiring major risk surgery, particularly those with associated systemic disease, should be considered for preoperative exercise stress testing, stress echocardiography and other noninvasive assessments of cardiac function.
These measurements are designed to evaluate cardiac reserve and to identify more precisely the degree of surgical risk. Mortality and morbidity may be diminished by intensive perioperative medical and nursing care.
The risk of surgery is increased in patients with cardiac disease. The risk rises with increasing severity of disease, becoming prohibitive if surgery is performed within six weeks of myocardial infarction. When assessing a patient with cardiac disease, it is necessary to predict the risk to the patient if surgery is not performed or is delayed, as well as the additional risk that the presence of cardiac diseases adds to the procedure.
Urgent operation must be performed regardless of the severity of cardiac disease when conditions such as massive haemorrhage, visceral perforation, strangulating intestinal obstruction or ruptured aortic aneurysm pose an immediate threat to life.
Elective surgery, however, is contraindicated when there is angina of recent onset, unstable angina, recent myocardial infarction, severe aortic stenosis, a high degree of atrioventricular heart block, severe hypertension and untreated congestive cardiac failure. Within three months of an acute infarct (which in 50% of cases is silent), the reinfarction rate after operation is 25%, with a perioperative mortality of more than 50%. The added risk of surgery stabilises at 5% after six months.
The increase in operative mortality is therefore minimal and stable (3–5%) in patients with cardiac disease with New York Heart Association class I or II angina, who have no change in their serial ECG pattern, where more than six months have passed since an acute myocardial infarction and where no clinical evidence of heart failure exists.
Time should be set aside before elective surgery to control concurrent cardiac disease, particularly unstable disease. Time spent in improving the patient’s condition is well spent and will make surgery safer. The introduction of beta-blocker therapy to slow the heart rate, and occasionally myocardial revascularisation, either by percutaneous coronary intervention or by coronary artery bypass surgery, may be necessary to prepare a patient for an essential elective surgical procedure on another system.
Cardiac patients are particularly sensitive to a fall in venous return (and thus coronary perfusion) and to hypoxia, especially when they are also anaemic (Box 10.4). In most cases hypovolaemia is the cause of diminished venous return during surgery but septicaemia, vasodilator drugs and hypercapnia are other causes. Occasionally, the pneumoperitoneum induced for laparoscopic abdominal procedures may reduce venous return. Patients with chronic obstructive airways disease tend to accumulate pulmonary interstitial fluid and, unless care is taken in high-risk patients, diminished pulmonary gas transfer will produce hypoxia and increase the danger of cardiac complications. Postoperative pain leads to increased catecholamine release and an increased incidence of arrhythmias.
Box 10.4
Common perioperative factors that precipitate cardiac decompensation
Hypotension
Hypoxia
Anaemia
Hypokalaemia
History
Patients with recent onset angina, unstable angina and crescendo angina are identified. The evidence for recent myocardial infarction should be reviewed and the time from infarct noted. A history of palpitations suggests the presence of potentially serious arrhythmias or serious conduction defects. A history of exertional dyspnoea, cough, fatigue, paroxysmal nocturnal dyspnoea orthopnoea and leg oedema suggests the diagnosis of congestive cardiac failure or that heart failure under treatment is poorly controlled. The major risk factors associated with ischaemic disease are outlined in Box 10.5. Anaemia may unmask anginal symptoms. Most of the risk factors (apart from anaemia) will require considerable time to reverse.
Box 10.5
Risk factors for ischaemic heart disease
Obesity
Hyperlipidaemia
Hypertension
Diabetes
Smoking
Physical examination
Assessment concentrates on detecting signs of: heart failure (raised jugular venous pressure, cardiomegaly, gallop rhythm, basal lung crepitations, hepatomegaly and dependent oedema); significant murmurs, especially those of aortic stenosis and mitral stenosis or regurgitation; hypertension; arrhythmias and conduction defects; and carotid artery stenosis.
Diagnostic and treatment plan
Noninvasive monitoring
In high-risk patients ECG monitoring is essential — this measure should be routine during surgery in patients aged over 45 years. An ECG is the basic diagnostic examination for cardiac disease and may reveal ischaemic change including infarction, digitalis toxicity, electrolyte abnormalities, conduction defects and arrhythmias. A patient with a recent myocardial infarct or suffering from angina may, however, have a normal ECG; also, ECG evidence of a well-established old infarct may not be of serious prognostic significance. Anaemia should be excluded by blood examination, diabetes by urinalysis and electrolyte abnormalities such as hypokalaemia by serum electrolyte levels. In the routine, low-risk elective case the simplest way of assessing a patient’s risk of cardiac decompensation is by assessing exercise tolerance.
Invasive monitoring
Invasive monitoring is indicated in elective as well as emergency surgery for patients with diminished cardiac reserve. This applies particularly to major surgery in elderly patients and those with severe coronary artery disease, conduction defects or severe aortic stenosis. A radial arterial line is used to monitor arterial blood pressure. Monitoring of the left atrial pressure and pulmonary artery pressures with a Swan-Ganz catheter and serial measurement of oxygen tension in the blood and arteriovenous oxygen differences are sometimes necessary. Thermodilution techniques using a Swan-Ganz catheter, together with measurement of oxygen consumption and CO2 production, can provide serial monitoring of cardiac output, stroke volume and ventilatory equivalents of oxygen and carbon dioxide. Many such patients are also at high risk of respiratory failure.
Common cardiac problems
It is important to control certain cardiovascular problems before operation (Box 10.6).
Box 10.6
Cardiovascular problems to be controlled before operation
Congestive cardiac failure
Ischaemic heart disease
Valvular heart disease
Arrhythmias
Hypertension
Oral anticoagulants
Congestive cardiac failure
The operative risk in patients with congestive cardiac failure relates closely to exercise tolerance. Dyspnoea on level walking, paroxysmal nocturnal dyspnoea orthopnoea, gallop rhythm, raised jugular venous pressure and basal lung crepitations suggest that elective surgery should be delayed for at least a month. Treatment with afterload reduction (e.g. angiotensin converting enzyme inhibitors), digitalis and diuretics is begun, taking care to avoid digitalis toxicity and hypokalaemia from diuretics. Beta-blockers (e.g. carvedilol) and other anti-failure medications may also be required. If resuscitation is necessary, care should be taken to avoid an excess of sodium in the infusate. It is preferable to use packed cells rather than whole blood for transfusion, to reduce both sodium infusion and the volume transfused.
Ischaemic heart disease (coronary artery disease)
The main danger from coronary artery disease is perioperative acute myocardial infarction. The incidence of infarction is increased if resuscitation is inadequate, especially in the presence of hypoxia and anaemia. Infarction may be heralded by an arrhythmia such as lethal ventricular fibrillation. The introduction of beta-blocker therapy to slow the heart rate and occasionally, myocardial revascularisation either by percutaneous coronary intervention or by coronary artery bypass surgery, will need to be done first in preparation for subsequent high-risk but semi-urgent surgery.
Valvular heart disease
The main types of valvular disease that significantly increase the risk of surgery are severe aortic stenosis and mitral stenosis. Patients with aortic stenosis and left ventricular hypertrophy have a lowered cardiac output, a much reduced cardiac reserve and a limited ability to compensate for blood loss. Patients with tight mitral stenosis can develop pulmonary oedema, particularly if they suddenly develop atrial fibrillation. There are also dangers of subacute bacterial endocarditis and of peripheral arterial embolism in patients with valvular disease. Patients on anticoagulants after valve replacement pose another problem.
Arrhythmias (and conduction defects)
Patients with chronic atrial fibrillation with a well-controlled ventricular rate and those with asymptomatic left and right bundle branch block do not present a significantly increased hazard during surgery. A high degree of atrioventricular block is more dangerous. A transvenous right ventricular electrode should be in situ during surgery so that the heart can be paced if required. Persistent pain and poorly controlled hypotension can trigger arrhythmias as a result of excess catecholamine release and cardiac ischaemia. Intra-operative arrhythmias may also be triggered by halothane, sympathomimetic drugs, digitalis toxicity or hypoxia. Postoperative arrhythmias may follow myocardial infarction, hypokalaemia, hypoxia, alkalosis and digitalis toxicity. Ventricular arrhythmias are most commonly a result of infarction or ischaemia in the hypoxic or hypovolaemic patient with reduced coronary perfusion. Supraventricular arrhythmias may be triggered by hypokalaemia.
Hypertension
Elective surgery poses little danger to patients with uncomplicated hypertension if the diastolic blood pressure is less than 100 mmHg, provided there is no heart failure and renal function is normal. With modern antihypertensives most patients can be maintained on their treatment up to and including the day of surgery. Postoperative hypotension may occur with catecholamine depletion secondary to antihypertensive agents such as methyldopa. It is essential to check for the presence of hypokalaemia before surgery in patients who have been treated with thiazide diuretics. Good anaesthetic management is a more important factor than preoperative adjustment of drug dosages in the prevention of hypertensive complications.
10.4 Respiratory disease
The major risk factor associated with obstructive airways disease is smoking. It can be assumed that smoking more than 20 cigarettes per day for 10 years or more will be associated with significant chronic airways disease. In patients with chronic obstructive pulmonary disease (COPD) the risk of surgery is increased because of postoperative atelectasis, acute infection and respiratory failure. The onset of respiratory failure can be difficult to anticipate, as signs of respiratory difficulty may not be identified before surgery. This is especially the case in sedentary patients. The best clue to the diagnosis is a reduced exercise tolerance.
Patients with chronically damaged lungs tend to retain sodium and water in the lungs after rapid transfusion or minor degrees of over-transfusion. This leads to a gas transfer defect and hypoxia, with alveolar collapse and subsequent infection. These are harbingers of a chain of events that can lead to a seriously ill patient with adult respiratory distress syndrome (ARDS) and progressive MOF.
Emergency surgery in patients with a full stomach adds the danger of pulmonary aspiration, which will dramatically worsen respiratory failure. The risk of respiratory complications varies with the form of surgery that is planned. Upper abdominal incisions, particularly vertical ones, significantly reduce lung capacity in the postoperative period. This is accentuated when pain control is inadequate. Opiates are best administered by constant infusion so that respiratory depression is minimised. Local analgesic techniques such as intercostal nerve blocks are often used to control postoperative pain and to diminish the risk of excessive sedation and underventilation.
History and physical examination
Acute upper respiratory tract infection and bronchitis with evidence of coryza, pharyngitis, tonsillitis or bronchitis with cough and yellow sputum is an indication to postpone elective surgery. Cough is the most common symptom of chronic respiratory disease. Mucoid sputum suggests tracheobronchitis and asthma; yellow or greenish sputum, bacterial infection; foul-smelling sputum, anaerobic infection such as lung abscess; and rusty sputum is typical of pneumococcal pneumonia. Bronchitis is the most common cause of haemoptysis; other causes include tuberculosis, carcinoma and bronchiectasis. Exertional dyspnoea is a further symptom of obstructive airways disease. Exercise tolerance should always be tested if respiratory insufficiency is suspected, especially in sedentary patients and in all smokers. Acute pulmonary infection can produce marked dyspnoea at rest, frequently with pleuritic chest pain. Orthopnoea suggests heart failure, but patients with bronchial asthma often breathe more easily in the sitting position as well. In bronchial asthma, wheezing is paroxysmal and diffuse. With bronchial narrowing, wheezing occurs during expiration and may only be induced on forced expiration or with exercise. A past history of an occupational hazard such as coal dust inhalation, allergies, respiratory illness, including tuberculosis, and thoracic surgery will highlight the need for special preparation before surgery.
Physical signs may be minimal with localised crepitations only. In bronchopneumonia with patchy consolidation, bronchial breathing is frequently absent. Collapse is characterised by moderate impairment of the percussion note with diminished breath sounds, a prolonged expiratory phase and an expiratory wheeze.
Diagnostic plan
Routine tests include posteroanterior and lateral chest X-ray, blood examination for anaemia, sputum culture and ECG.
Spirometry and arterial blood gas estimation are mandatory in patients with evidence of incipient respiratory failure (limitation in exercise tolerance because of exertional dyspnoea and a forced expiration time of greater than five seconds). Testing is also indicated in: patients undergoing major surgery of the upper abdomen or chest; the elderly; patients with cough, sputum, wheezing or asthma; and those with a history of heavy smoking (Box 10.7).
Box 10.7
Indications for preoperative lung function tests
History of exertional dyspnoea
History of cough, sputum, wheeze
History of heavy smoking
Forced expiration time >7 seconds
Planned major surgery on upper abdomen or chest
Postoperative respiratory failure is almost inevitable (Box 10.8) if:
• the vital capacity (VC) is less than 1 L (normally 4–8 L)
• the forced expiratory volume in one second (FEV1) is less than 400 mL (normally 4000 mL)
• the PaO2 is less than 50 mmHg (normally 75–100 mmHg) and the PaCO2 is greater than 45 mmHg (normally 35–40 mmHg).
Box 10.8
Indicators of critically impaired lung function
VC <1 L (N 4–8 L)
FEV1 <400 mL (N 4000 mL)
PaO2 <50 mmHg (N 75–100)
PaCO2 >45 mmHg (N 35–40)
Respiratory failure can be precipitated after major or emergency surgery when there is only moderate obstructive airways disease. A FEV1 of 2.0 L will be reduced after operation to below the critical level in most patients subjected to major upper abdominal surgery. In high-risk patients, preparation for surgery should include serial studies of respiratory function to measure the response to treatment, which is based upon stopping smoking and having chest physiotherapy. Bronchodilators are added if pulmonary function tests show significant bronchospasm. Particular care should be taken during and after surgery to prevent pain, underventilation and hypoxia.
Prevention and treatment plan
Patients with chronic obstructive airways disease should stop smoking for at least two weeks, and preferably four weeks, before surgery. The program of preparation includes chest physiotherapy, postural drainage, antibiotics according to sputum culture and for bronchospasm, inhaled bronchodilators. A course of formal preoperative pulmonary rehabilitation may be appropriate
In many patients considered previously unsuitable for elective surgery, improvement occurs, enabling surgery to be performed with relative safety. In patients with severe respiratory damage requiring emergency surgery, postoperative respiratory failure must be anticipated and measures planned for respiratory support to increase the chance of survival. Of major importance is the continuation of postoperative ventilatory support. Intermittent positive pressure ventilation continues until continuous sampling of radial arterial blood shows control of hypoxaemia.
The successful management of established respiratory failure is intimately related to maintenance of cardiac function; particular care should be taken to correct hypovolaemia promptly, but volume loading must be cautious to avoid sudden increases in the venous return that may promote pulmonary oedema. Serial measurement of the atrial pressure by a Swan-Ganz catheter and of cardiac output adds greater precision to volume control. The left atrial pressure is maintained as low as is compatible with normal blood pressure and peripheral perfusion. If the serum creatinine rises, dopamine is administered in small dosage to maintain renal blood flow and urine output (renal dopaminergic treatment). Packed cells rather than whole blood should be used for transfusion.
10.5 Cerebrovascular disease
Cerebrovascular accidents can occur in the perioperative period in older patients with severe atherosclerosis as a result of elective or emergency surgery, particularly when blood pressure suddenly falls. During surgery in patients with cerebral atherosclerosis, careful maintenance of venous return and of blood pressure is essential to preserve both coronary and carotid blood flow. Patients with clinical evidence of carotid artery stenosis have an increased risk of stroke after major surgery. Little can be done in the emergency situation, but for elective major surgery carotid endarterectomy should be performed beforehand in patients with a history of transient ischaemic attacks (TIAs). Microemboli from internal carotid atherosclerotic ulceration produce transient paresis or numbness of the controlateral arm or leg and temporary loss of vision (amaurosis fugax).
Identification of an asymptomatic carotid bruit may be the first indication of cerebrovascular disease. Noninvasive duplex Doppler studies can help categorise the stenosis and help determine if antiplatelet agents or carotid surgery is indicated prior to dealing with the presenting elective surgical problem.
10.6 Alcoholic liver disease
Alcoholism can be difficult to detect. The amount consumed and length of history are often concealed. In most cases, signs of liver disease can be found that suggest the diagnosis. The degree of liver damage is directly related to the amount of alcohol consumed. Alcoholic liver disease is a common associated problem in both emergency and elective surgical patients. Elective surgery should be delayed in the presence of moderate or severe alcoholic liver disease. In most patients general health and liver function can be much improved by a period of abstinence and chest physiotherapy, especially in those patients who smoke heavily. Emergency surgery often causes a decompensation in liver function in patients with severe cirrhosis, especially with surgical conditions associated with sepsis, bleeding, electrolyte disturbances (hypokalaemia, metabolic alkalosis and acidosis), hypoxia and hypoglycaemia. Sedatives, narcotics, tranquillisers and antibiotics require very careful control of dosage. Most are metabolised and excreted by the liver; portal-systemic venous shunting due to liver disease results in oral agents having an effective 10–20-fold increase in systemic drug delivery, requiring reduction of oral drug dosage.
Complications arising from alcoholic liver disease
There are a number of major problems and complications that can arise in the surgical patient with alcoholic liver disease (Box 10.9). Each is explained in turn.
Box 10.9
Problems associated with alcoholic liver disease
Malnutrition — vitamin deficiency
Sepsis
Respiratory failure
Coagulation disorders
Operative or gastrointestinal bleeding (portal hypertension)
Cardiomyopathy
Renal insufficiency
Hepatic insufficiency
Delirium tremens
Malnutrition and vitamin deficiency (especially thiamine) contribute to poor wound healing. The degree to which serum albumin is reduced is the best measure of prognosis in these cases.
Sepsis is increased because of malnutrition, poor hygiene and immunosuppression.
Respiratory failure is common; most patients have associated smoking-induced lung damage. Pulmonary sepsis, increased lung water and a tendency to pulmonary oedema are common complications. Depressed cough reflex and underventilation are common because of delirium, encephalopathy and increased sensitivity to sedatives and narcotics. Congestive cardiac failure often accentuates hypoxia because of increased pulmonary congestion or pulmonary oedema.
Coagulation disorders with a bleeding tendency are frequent. Anticoagulants (heparin and warfarin) are cleared by the liver and are generally contraindicated in liver disease. Poor haemostasis occurs because of reduced prothrombin production by the failing liver, thrombocytopenia secondary to hypersplenism and dilutional coagulopathy from massive blood transfusion. This may result in significant operative bleeding.
Portal hypertension with collateral vein development increases the technical difficulties encountered during abdominal surgery and therefore the technical complication rate. Gastrointestinal haemorrhage from oesophageal varices is an ever-present risk.
Cardiomyopathy with heart failure (as well as ischaemic heart disease) is common in patients with alcoholism, increasing the danger of cardiac decompensation, especially under the conditions of a surgical emergency.
Associated renal insufficiency is common. Hepatic insufficiency and jaundice are additional risk factors in the development of renal injury after surgery (hepatorenal syndrome).
Exacerbation of hepatic insufficiency can follow the stress of surgery, particularly in patients in whom blood loss, infection and water and salt deficiencies are major manifestations.
Delirium tremens is a common cause of acute brain syndrome after surgery. Diagnosis of alcohol withdrawal as the cause is made more difficult if the patient is a secret drinker.
History and physical examination
Significant alcohol consumption is often denied and the diagnosis of alcoholic cirrhosis thus rendered difficult. Signs of liver failure are sought; an enlarged firm liver will often alert the clinician to the possible diagnosis. The initial symptoms of alcoholic liver disease are weakness, fatigue, insomnia, weight loss, anorexia and nausea, loss of libido and impotence — symptoms very similar to those of depression, a disorder that is often associated with alcoholism.
Examination may reveal few signs, apart from hepatomegaly. A dishevelled appearance and alcoholic facies may arouse suspicion of the diagnosis. Systemic signs of liver disease include palmar erythema, leuconychia, spider naevi, loss of body hair, gynaecomastia, testicular atrophy, evidence of vitamin deficiencies, glossitis and cheilosis. Overt signs of liver failure include jaundice, ascites, wasting and encephalopathy. Jaundice can occur early from alcoholic hepatitis or cholestasis, often precipitated by a drinking spree. Wernicke’s encephalopathy (a reversible brain syndrome due to thiamine deficiency) and Korsakov’s psychosis (in which brain damage is usually irreversible) may also be evident. Sudden deterioration in liver function may sometimes be due to the development of hepatoma. Congestive heart failure is common. Splenomegaly, a major sign of portal hypertension, may be detectable.
Diagnostic plan
Routine tests (Box 10.10) include blood examination, liver function tests including coagulation screening, serum amylase, chest X-ray and ECG. The level of serum albumin is the best general measure of prognosis. In many cases respiratory function tests are necessary because of significant obstructive airways disease. Abdominal ultrasound, abdominal CT scan and liver biopsy may be indicated when the diagnosis is in doubt.
Box 10.10
Preoperative testing in chronic liver disease
Full blood examination
Liver function tests (serum albumin)
Coagulation profile
Serum lipase
Chest X-ray
ECG
Treatment plan
Surgery in the patient with alcoholic liver disease is difficult and demanding. Meticulous resuscitation, the correct choice of operative procedure for the surgical problem at hand, the careful timing of surgery and scrupulous technique are of particular importance if surgery is to be completed successfully. These patients are prone to postoperative cardiorespiratory failure, haemorrhage, poor wound healing and sepsis. The general factors in management that require special attention are:
• accurately maintaining circulating blood volume, with inotropic support if necessary, using fresh blood transfusion for resuscitation and means to prevent the development of bleeding disorders
• correcting anaemia prior to operation
• giving vitamin K parenterally for several days before surgery to correct prothrombin deficits
• providing respiratory support with endotracheal intubation for airway protection and assisting ventilation in patients with worsening pulmonary gas transfer
• preventing hepatic coma by limiting protein intake and evacuating blood from the intestine; lactulose by nasogastric tube will encourage bowel emptying and trap ammonia in the large bowel (gastrointestinal peptic ulcer prophylaxis with proton pump inhibitors may be used and oral and systemic prophylactic antibiotics given in the perioperative period)
• providing liver nutritional support by parenteral infusion of concentrated glucose, branched chain amino-acids, vitamin supplements and thiamine
• meticulous correction of water, electrolyte and acid–base abnormalities (hypoglycaemia must be monitored and corrected)
• prophylaxis and treatment of infections that may precipitate hepatic coma; a short course of perioperative antibiotic prophylaxis combined with close postoperative surveillance for evidence of infection and prompt therapy for any established infection will minimise this risk
• carefully monitoring drug dosage, particularly those drugs cleared by the liver and those that affect cerebral function (Box 10.11)
• anticipating delirium tremens despite all the above measures. Delirium is often presaged by prodromal symptoms of agitation and confusion and is treated by additional nutritional and vitamin support supplemented by chlormethiazole or diazepam infusion.
Box 10.11
Drugs cleared predominantly by the liver
Adriamycin
Azathioprine
Cyclophosphamide
Cyclosporine
Heparin
Lignocaine
Metoprolol
Morphine
Oxyprenolol
Phenytoin
Propranolol
Theophylline
Vincristine
Warfarin
10.7 Chronic renal disease
Chronic renal disease is often subtle in its presentation and it is wise to assess renal function in all patients aged over 40 years, when major surgery is planned. When forewarned of chronic renal disease, elective surgery usually does not need to be delayed. Patients with chronic renal disease are commonly polyuric and acute deterioration in renal function can occur if they become water or saline depleted. Acute renal failure is the most significant complication of chronic renal disease; prevention demands strict attention to fluid and electrolyte balance (especially avoiding dehydration and maintaining a stable level of serum potassium), identification of high-risk patient groups and accurate replacement of blood loss during surgery. Apart from acute renal failure, the main complications of surgery in patients with chronic renal failure are sepsis (including urinary tract infection), poor wound healing, cardiovascular complications such as myocardial infarction and cerebrovascular accident.
Diagnostic plan
History and physical examination, when combined with a complete urinalysis and measurement of serum creatinine and serum albumin, will usually establish or exclude the presence of unsuspected renal disease. Creatinine clearance can be determined by a variety of rapid biochemical or radionuclide techniques or by nomograms involving age, body weight, sex and plasma creatinine. The symptoms of chronic renal failure are nonspecific and include anorexia, weight loss, fatigue, nocturia, dysuria, polyuria and sometimes haematuria. On examination the patients are pale, with sallow pigmentation and may have purpura. Hypertension is common, with retinal and cardiac complications. Urine examination reveals a low urine specific gravity, dysmorphic red cells, renal casts and proteinuria. Organisms may be grown on culture. Blood and serum examination usually reveals a normochromic normocytic anaemia, low serum albumin, raised serum creatinine and variable electrolyte abnormalities.
Treatment plan
Important aspects of preoperative preparation in patients with chronic renal failure are summarised in Box 10.12. Hypertension and urinary tract infection may need treatment before elective surgery can proceed. Unless absolutely necessary, urinary catheterisation should be avoided. Transurethral prostectomy may be necessary to relieve bladder neck obstruction before elective surgery. Patients with anaemia or renal failure survive with quite low haemoglobin levels, due to an increase in 2, 3–diphosphoglycerate (2, 3–DPG) promoting better transfer of oxygen at the tissue level. Injudicious blood transfusion in a normovolaemic haemodiluted patient may reduce renal blood flow by increasing blood viscosity and can precipitate an exacerbation of renal failure. Thus a haemoglobin level of 8–9 g/dL in patients with chronic renal disease may be adequate for major surgery and not require transfusion. As many drugs are nephrotoxic, particular care must be taken with prescribing (Box 10.13).
Box 10.12
Preoperative preparation of patients with chronic renal disease
Control urinary tract infection and urinary tract obstruction. Urinary catheterisation should be avoided if possible.
Control hypertension.
Watch for drug nephrotoxicity — particularly nephrotoxic antibiotics.
Careful preoperative hydration and strict attention to fluid balance. Solute diuretic infusion in high-risk cases (mannitol 20 g).
Box 10.13
Nephrotoxic drugs
Antibiotics: aminoglycosides, sulfonamides, amphotericin B, tetracycline, cephalosporins
Contrast media
Fluorinated anaesthetics
Cytotoxics
Phenacetin and NSAIDs
Metformin
As each nephron either functions normally or ceases to function with disease (intact nephron principle), creatinine clearance (Ccr) is an excellent marker of the degree of dose reduction required. If the Ccr is 50% of normal, all drugs cleared by the kidney need 50% reduction in dose. Drugs that are the worst offenders are aminoglycoside antibiotics (gentamicin), analgesics such as phenacetin and NSAIDs, oral hypoglycaemic agents and methoxyflurane. As digoxin is mainly excreted by the kidneys, digitalis toxicity is a common problem in patients with chronic renal failure. Examples of drugs mainly cleared by renal mechanisms are shown in Box 10.14.
Box 10.14
Drugs cleared mainly by the kidney
Acyclovir
Amikacin
Colistin
Digoxin
Gentamicin
Kanamycin
Lithium
Streptomycin
Tobramycin
Vancomycin
In patients not requiring maintenance dialysis and after cautious correction of severe anaemia, management concentrates on preoperative hydration and strict attention to fluid balance during and after surgery. High-risk patients (major vascular surgery, jaundiced and diabetic patients, and those with chronic renal insufficiency) are also given a slow infusion of a solute diuretic during surgery (mannitol 20 g) with careful monitoring of urine output.
Patients with renal impairment present a dilemma with respect to preoperative contrast imaging, owing to the potential nephrotoxicity of the contrast agent. Those patients with mild renal impairment may undergo contrast studies with attention to pre-procedural intravenous hydration, cessation of metformin if prescribed, administration of oral N-acetylcysteine for potential renal protection and contrast dose reduction.
Patients on dialysis are more susceptible to infection and maintenance of the fluid and electrolyte balance is more difficult. Dialysis is reinstituted as early after surgery as haemostasis will allow. Peritoneal dialysis is preferable to haemodialysis if both are available.
Acute tubular necrosis may occur, especially in the high-risk patient, after emergency or complicated surgery. Oliguria in these patients commonly has a correctable hypovolaemic prerenal component to it. Bladder neck obstruction should always be excluded. In patients with a poor response to a fluid load or diuretic measures and a raised urinary sodium, where incipient acute renal failure is likely to be present, preparations for dialysis should be taken as soon as possible (Box 10.15). Extrarenal factors that may contribute to deterioration of renal failure — such as sepsis, fluid and electrolyte disturbances, drug toxicity and inadequate nutrition — should also receive careful attention.
Box 10.15
Acute renal injury — indications for haemofiltration or dialysis
Prevention of clinically overt uraemia
Control of hyperkalaemia
Correction of acidosis
Correction of fluid overload
To allow liberal fluid and nutritional therapy
10.8 Haemostatic and haemopoietic disorders
The possibility of a coagulation disorder should be considered in all patients undergoing major surgery. This especially applies to surgery for malignant disease.
Most episodes of excessive bleeding during surgery are due to local surgical or anatomical defects rather than to coagulation disorders; bleeding from a single site without a history of excessive bruising or previous bleeding is usually from an unligated vessel. Bleeding may be primary (intra-operative), reactionary (occurring within 24 hours of surgery, bleeding from vasoconstricted vessels being reactivated as blood pressure returns to normal) or secondary (which occurs after about a week and is due in virtually all cases to septic necrosis of blood vessels). Unless strong evidence exists that a coagulation defect was present or has developed re-operation will be necessary to achieve haemostasis in most instances of reactionary or secondary haemorrhage. Local control of secondary haemorrhage can be very difficult in the presence of local infection.
Sometimes unexpected bleeding can be traced to a generalised defect in haemostasis (Box 10.16). The most common defect of coagulation encountered in surgical practice is prior treatment with oral anticoagulants or antiplatelet agents. Precise diagnosis and correct management require knowledge of the intrinsic and extrinsic pathways to fibrin formation (Fig 10.1) and the formation and the function of platelets. The initial response when a vessel is divided is for it to constrict (Box 10.16). This, combined with platelet aggregation and adherence and plasma coagulation, stops the bleeding. Platelets adhere to an endothelial defect and react with collagen to perpetuate vasoconstriction and produce further platelet aggregation. Exposure of plasma to connective tissue activates specific plasma enzymes and clotting factors, initiating the coagulation cascade. This generates thrombin and ultimately leads to the conversion of fibrinogen to fibrin clot, reinforcing the friable platelet aggregate. Initiation of coagulation also leads to the activation of plasminogen that releases plasmin, a fibrinolytic factor. Plasmin is a natural defence against pathological extension of fibrin deposition.
Box 10.16
Components of normal haemostasis
Vascular constriction
Platelet aggregation and adherence
Coagulation forming fibrin clot
Figure 10.1 Mechanisms of coagulation
From Kumar & Clark, 2005
Common causes
1. Medications: oral anticoagulant (e.g. warfarin) or antiplatelet (e.g. aspirin or clopidogrel) therapy; heparin or clexane therapy
2. Liver disease and disorders of prothrombin production
3. Platelet disorders and haematological malignancies
4. Consumption coagulopathy
5. Haemophilia, Christmas disease and Von Willebrand’s disease
Clinical assessment
Extensive laboratory investigation for the presence of a bleeding tendency is not required in the routine assessment of an apparently healthy patient. Most haemorrhagic disorders of significance can be suspected during a careful history and physical examination that specifically check for:
• any significant past episodes of bleeding
• whether the onset was in childhood, suggesting a congenital disorder, or of recent onset, suggesting an acquired disorder
• circumstances under which bleeding occurred, such as minor surgery or injury, dental procedures, after a fall or during contact sports
• unusual posttraumatic swellings of joints or soft tissue. Bleeding into joints is characteristic of haemophilia, as is a family history, especially when the sex-linked recessive pattern of the disorder is evident from the family history.
The character of the bleeding may also be helpful. Purpura or petechiae suggest a capillary or platelet defect, rather than haemophilia. Large ecchymoses, haematomas and haemarthroses suggest haemophilia. Massive bleeding from a single site after surgery suggests a technical fault rather than a bleeding disorder. In contrast, sudden severe bleeding from multiple sites after prolonged surgery or during obstetrical procedures suggests an acquired fibrinogen deficiency.
The drug history is of particular importance. Recent ingestion of drugs known to influence haemostasis adversely, such as aspirin, clopidogrel and nonsteroidal anti-inflammatory agents oral anticoagulants, quinidine, quinine, thiazides, sulfonamides, phenylbutazone and gold should be checked.
Diagnostic plan
Tests relating to coagulation, platelet function and vascular abnormalities include the following.
Whole blood clotting time
This theoretically measures the intrinsic coagulation system in its entirety but is insensitive and variable and too difficult to standardise.
One-stage prothrombin time (PT)
This measures the time in seconds required to form a clot in citrated plasma after calcium and a standardised tissue thromboplastin have been added. It thus reflects the extrinsic clotting system from factor VII through the common pathway involving prothrombin and fibrinogen. It is most sensitive to factor VII deficiency and is the standard method of monitoring anticoagulant treatment with vitamin K antagonists and in detecting problems in patients with liver failure. The international normalised ratio (INR) is used to assess the control of oral anticoagulant treatment. It represents the ratio of the patient’s PT to a normal control based on an international reference thromboplastin, which ensures standardisation of anticoagulation between different centres.
Partial thromboplastin time (PTT, APTT)
This uses a platelet factor analogue instead of a tissue thromboplastin but is otherwise similar to PT. Activated PTT (APTT) also uses kaolin to ensure full activation of factor XII. The test thus measures the intrinsic clotting system in a reproducible and sensitive manner. It reflects changes in patients with factor VIII deficiencies (haemophilia and Christmas disease), is used to regulate heparin dosage and also to monitor coagulation disorders in liver disease.
Thrombin time
This measures the time required for plasma to clot after the addition of a standard amount of thrombin and thus measures conversion of fibrinogen to fibrin.
Fibrinogen concentration is measured directly.
Tests of platelet function
These include platelet count (the single most important and helpful test), bleeding time, tests for provoked petechiae, measurement of platelet aggregation and many other sophisticated and specialised tests.
Bleeding time. The skin bleeding time is the time taken for bleeding to stop after a skin cut is made. It is dependent mainly on platelet function and a variable vascular constrictive component. It requires a carefully standardised technique to be reproducible and reliable.
Hess test. This clinical test can be used if thrombocytopenia or capillary fragility is suspected, for example, in patients with purpura. A sphygmomanometer cuff over the upper arm is inflated to midway between the systolic and diastolic pressures for five minutes. It is then deflated and an area on the forearm or cubital fossa that has been previously demarcated is examined for petechiae. If positive, the platelet count should be checked to distinguish between thrombocytopenic and nonthrombocytopenic causes of purpura.
Tests of fibrinolysis
These include kits to measure fibrin degradation split products.
Healthy young patients undergoing routine surgery do not need haematological screening. Those aged over 40 years should have, in addition to careful history and physical examination, a blood count, a PT, INR and PTT. Elderly patients (aged over 70 years) should have a platelet count as well. Patients with hepatic or renal or other systemic diseases should have similar screening to the elderly.
The preoperative detection of thrombocytopenia (<100 × 109/L) is very important in evaluating bleeding disorders. On examination of the blood smear there are normally six to 10 platelets per high-power field. Thrombocytopenia can occur as a complication of recent infection or drug ingestion. Splenomegaly is an important associated physical sign. Additional tests of platelet function are indicated when splenomegaly is found on physical examination, the bleeding time is prolonged or the Hess test is positive.
Treatment plan
1 Patients on oral anticoagulants or antiplatelet agents
Surgery in patients given coumarin derivatives (warfarin) is relatively safe when the PT is greater than 25% of normal and thus in the range where protection by warfarin against thromboembolism is lost. It is therefore best to stop warfarin well before (five to seven days) elective surgery, convert to heparin or clexane and then stop heparin or clexane just before operation, thus minimising the time when the patient is unprotected from risks of thrombosis and embolisation.
In patients requiring emergency surgery 5 mg of vitamin K intravenously will restore prothrombin levels to greater than 40% within four hours and to normal in 24 to 48 hours. These patients then remain refractory to oral anticoagulants for a week. Immediate and transient restoration to normal PT can be produced by fresh frozen plasma that restores factor II, VII and IX levels lowered by coumarin therapy. The patient can be started on heparin after emergency surgery when haemostasis allows — usually about 24 hours after operation. Heparin is continued until the refractoriness to coumarin can be expected to have resolved, at about one week after surgery.
For elective surgery coumarin derivatives are stopped 5–7 days before surgery and the INR monitored. Heparin or clexane is commenced in the usual anticoagulant dosage and stopped 6–12 hours before surgery. Heparin or clexane is recommenced when haemostasis will allow this with safety. For urgent reversal of heparin, protamine sulfate can be given by slow intravenous infusion. Oral anticoagulants can normally be started again when oral feeding is re-established. The greatest danger of embolic complications in patients taken off anticoagulants is in those with prosthetic cardiac valves, more so than in patients with atrial fibrillation.
Aspirin and/or clopidogrel ingestion is often a factor in perioperative bleeding. Both reduce the capacity of platelets to aggregate. Where possible they should both be stopped at least five to seven days prior to elective surgery. Patients at high risk for arterial thrombosis (e.g. those with a drug-eluting coronary artery stent in situ) should be converted to heparin or clexane and managed as above during the perioperative period. The antiplatelet agents may be recommenced once oral intake has been re-established. For emergency surgery, it may be impossible to cease aspirin and/or clopidogrel in advance of the operation. If excessive bleeding is anticipated or occurs in this situation a platelet transfusion may be required.
2 Liver disease
In patients with liver failure there is reduced production of prothrombin by the liver, thrombocytopenia secondary to hypersplenism and a lower threshold to develop coagulopathy after massive blood transfusion. All patients require perioperative parenteral vitamin K and fresh frozen plasma when necessary.
3 Platelet disorders
Thrombocytopenia may develop as an allergic reaction to drugs, as a feature of leukaemia, with malignant destruction of bone marrow or from an auto-immune reaction (idiopathic thrombocytopenic purpura). Haemorrhagic complications are unlikely with a platelet count above 40 × 109/L. In idiopathic thrombocytopenic purpura, steroids often induce a rise in platelet count. Splenectomy produces a remission in two-thirds of cases. Replacement therapy requires fresh blood or infusion of a concentrated plasma preparation of platelets in a line without a filter.
4 Consumption coagulopathy
Consumption of clotting factors (including platelets) in the microcirculation may occur in the massively injured patient with tissue necrosis and sepsis, especially when compounded by massive transfusion of banked blood, which is poor in platelets and in labile factors V and VIII (Table 10.2).
Table 10.2 Changes during bank storage of whole blood at 4°C after two weeks
|
Plasma levels |
|
|
Hydrogen ion |
25 mmol/L |
|
Citrate |
5 mmol/L |
|
Potassium |
20–30 mmol/L |
|
Ammonia |
1 mg % |
|
Free haemoglobin |
20 mg % |
|
Particulate and antigenic debris |
|
|
Dead leucocytes — HLA |
|
|
Dead platelets |
|
|
Plasma protein antigens |
|
|
Red cells |
|
|
Early loss post-transfusion |
20% |
|
2,3–DPG |
Nil |
|
ATP |
Very low |
|
Osmotic fragility |
Increased |
|
Coagulation factors |
|
|
Factor V, VIII, IX |
10–20% or less |
|
Platelets |
Nil |
|
Calcium |
All chelated with citrate |
|
Fibrinogen |
Relatively normal |
Diagnosis depends on the demonstration of a deficiency in labile clotting factors and platelets. Treatment requires expert haematological diagnosis and assistance. In emergency situations of excessive bleeding at operation, steps are:
• exclude a technical surgical problem
• take blood samples for coagulation studies
• check for incompatible blood transfusion and intravenous haemolysis
• replace losses with:
• red cell concentrates
• fresh frozen plasma
• cryoprecipitate
• calcium supplements (20 mL per unit)
• platelet transfusions
• correct specific defects revealed by coagulation testing. Use platelet concentrates for thrombocytopenia and specific coagulation factors wherever possible, as these contain higher proportions than in so-called fresh blood. If urgent help is unavailable, use blood as fresh as possible. Recombinant factor VII may be indicated in severe, ongoing, coagulopathic bleeding refractory to the above measures.
5 Haemophilia, Christmas disease and Von Willebrand’s disease
Haemophilia A is an inherited sex-linked recessive trait that is associated with a deficiency of factor VIII (antihaemophilic globulin). Platelet function is unimpaired but the platelet clot is not reinforced by fibrin. The common clinical manifestation is bleeding into joints and soft tissues. Surgery should be avoided if possible but can be covered with increased safety by administration of concentrated factor VIII.
Christmas disease (haemophilia B, factor IX deficiency) is clinically indistinguishable from haemophilia.
Von Willebrand’s disease (pseudohaemophilia) is transmitted as an autosomal dominant trait and is also an abnormality of the factor VIII complex but causing a defect in platelet adhesion with a bleeding pattern more characteristic of a platelet defect.
10.9 Anaemia
As a general rule mild anaemia does not increase the risk of surgery. However, if time permits the cause of the anaemia should be identified before elective surgery. Iron deficiency anaemia is best detected early and treated by oral iron. Patients with the anaemia of renal injury are an exception to the general rule and can cope with quite low haemoglobin levels, due to an increase in red cell 2, 3–DPG that promotes a better transfer of oxygen at the tissue level. However, in all patients the combination of any degree of anaemia with decompensated cardiovascular disease (e.g. angina or obstructive airways disease) warns that intensive perioperative care will be necessary.
Causes of anaemia
The most common cause of anaemia is iron deficiency from blood loss, which may be occult. About 25% of patients have anaemia due to chronic disease; in about 10% of cases the anaemia is megaloblastic and in the remainder the anaemia is secondary to a haemolytic process or marrow depression. In the surgical patient, iron deficiency blood-loss anaemia is even more common.
Clinical features and diagnostic plan
Preoperative haemoglobin measurement should be performed as a routine examination in all patients. Patients may have significant anaemia but no symptoms if the anaemia has developed slowly over a period of months and the body has compensated for the decreased oxygen-carrying capacity through such physiological mechanisms as increased cardiac output. The signs and symptoms of anaemia vary with its severity and are more marked if the anaemia has developed over a short period.
Symptoms of weakness and tiredness, breathlessness, palpitations and angina can occur with moderate or severe anaemia. Pallor is the outstanding physical sign. Pallor of the conjunctival and palmar creases becomes apparent when the haemoglobin level falls below 10 g/dL. Tachycardia and cardiac failure may accompany severe anaemia.
Classification of anaemia is based upon the size and haemoglobin content of the red cells. These measurements are calculated from the haematocrit, the haemoglobin level and the red cell count. The average size of the red cells (mean corpuscular volume; MCV), the average amount of haemoglobin in each red cell (mean corpuscular haemoglobin; MCH) and the proportion of the total volume of the average red cell occupied by haemoglobin (mean corpuscular haemoglobin concentration; MCHC) are the main red cell indices. With rare exceptions anaemias fall into one of the three categories: microcytic hypochromic, normocytic normochromic and macrocytic normochromic. These correspond to the anaemias of iron deficiency, chronic disease and megaloblastosis.
The differentiation of iron deficiency anaemia from other types of anaemia is rarely difficult. Occasionally, the anaemia of chronic disease, haemoglobinopathies and sideroblastic anaemias may produce a hypochromic microcytic picture on the blood film. The major clinical difficulty in the surgical patient is the separation of iron deficiency anaemia that is secondary to chronic blood loss from the anaemia of chronic disease. The serum iron is decreased in both disorders. The serum ferritin levels are usually decreased in iron deficiency and raised in the anaemia of chronic disease. When doubt exists, total body iron stores can be assessed by marrow examination. Iron deficiency anaemia is the only anaemia with absent marrow iron stores. Reduced oral intake and absorption of iron is a very rare cause of iron deficiency anaemia.
Treatment plan
In the surgical patient, it is often possible to institute iron therapy prior to admission to hospital. Anaemia is thus always best diagnosed and its cause determined during the first office consultation in patients needing elective surgery. For iron deficiency blood-loss anaemia the oral iron therapy begins immediately so that anaemia can be safely corrected prior to surgery. Patients with moderate iron deficiency or haemolytic anaemias do not pose an excessive risk provided the haemoglobin level and the blood volume are adequate (>10 g/dL) and cardiorespiratory function is normal.
In patients with megaloblastic anaemia surgery should be deferred, if possible, until specific therapy such as vitamin B12 or folic acid has repaired the generalised tissue defect. In these cases transfusion alone may not render surgery safe, as protein metabolism of all cells is affected by the vitamin deficiency that causes the macrocytic anaemia. Adequate tissue levels can be achieved with one to two weeks’ oral treatment with vitamin B12 or folic acid or both.
If it is not possible to correct the anaemia in a timely manner, the patient may be given concentrated red cells prior to surgery. A period of three days should be allowed to elapse before operation as the transfused blood will not reach its maximum oxygen-carrying capacity until at least two days following transfusion. This period allows the transfused red cells to accumulate normal level of 2,3–DPG, necessary for efficient delivery of oxygen to the tissues, and allows for plasma dispersal restoring normovolaemia. Elective surgery should seldom be undertaken when the haemoglobin concentration is less than 9–10 g/dL. Patients with longstanding anaemia are able to tolerate a reduced level of haemoglobin better than those who have become acutely anaemic. This tolerance in chronic anaemia is a result of altered 2,3–DPG concentration in the red cells, with a favourable shift in the oxyhaemoglobin dissociation curve to the right.
10.10 Diabetes mellitus
Biochemical testing of the urine should be part of the initial clinical examinations of all patients. Too often the diabetic state is first diagnosed on routine ward testing when the patient enters hospital for surgery. Screening for diabetes begins by examination of the urine for sugar and ketones. Random blood sugar, fasting blood sugar, oral glucose tolerance testing and measuring glycosylated haemoglobin (HbA1c) as an indicator of diabetic control should be performed during the preoperative work-up in suspected or established diabetic patients. Uncontrolled diabetes (HbA1c level >7%) carries a greater risk of infective and other complications after surgery. Good preoperative diabetic control is essential and must be maintained during the postoperative period. Diabetes may be complicated after operation by ketoacidosis if systemic infection supervenes. The usual danger after operation, however, is not hyperglycaemia and ketosis from uncontrolled diabetes but hypoglycaemic reactions from insulin given without adequate carbohydrate intake. In surgical conditions associated with diabetic sepsis surgery must not be delayed unduly. Diabetes is associated with more virulent infections and control of diabetes may not be possible until sepsis is controlled, pus drained and necrotic tissue removed. Surgical conditions such as cholecystitis and appendicitis when associated with diabetes require urgent attention; diabetic gangrene is a surgical emergency if life and limb are to be saved.
Diagnostic and treatment plans
Diabetes mellitus should be brought under control prior to operation (Box 10.17).
Box 10.17
Preoperative management: diabetes mellitus
Surgical control of serious infection must not await full control of diabetes.
Prevention of hypoglycaemia from inadequate carbohydrate intake is more important than prevention of ketosis from diabetes.
Urinalysis for glucose, random blood sugar, fasting blood sugar, oral glucose tolerance testing (GTT), HbA1c levels constitute the work-up in suspected or established diabetics.
Assess for cardiovascular and cerebrovascular complications, even in young patients.
Schedule elective surgery in the morning as first case where possible.
Withhold oral hypoglycaemic agents and modify insulin dosage prior to surgery.
Diabetic patients are prone to atherosclerosis at a younger age and should be assessed for the presence of ischaemic heart disease, peripheral vascular disease, hypertension, renal disease and carotid stenosis. An ECG and chest X-ray are indicated in all cases. Renal function is assessed by measuring serum electrolytes and serum creatinine.
Diabetic retinopathy, peripheral neuropathy and autonomic neuropathy are important additional complications that must be checked for in all diabetic patients, as should evidence of infections and fluid and electrolyte disorders.
Mild elevation of blood glucose with detectable glycosuria is acceptable in the perioperative period to ensure that hypoglycaemia does not occur during any period of inadequate carbohydrate intake after surgery. If the patient has been on an oral hypoglycaemic agent, a continuous insulin infusion (CII) or intermittent (every six hours) doses of a short-acting insulin should be substituted if it is anticipated that postoperative feeding will be delayed.
Ideally any operation should be scheduled early in the day, following the normal nocturnal fast. Metformin should be ceased 24 hours prior to surgery due to the risk of lactic acidosis. All other oral hypoglycaemic agents (e.g. sulfonylureas, thiazolidinediones, acarbose) should be ceased when the patient is fasting. Insulin-dependent diabetic patients should have their morning dose of insulin withheld or modified depending on their regimen of insulin and timing of surgery to a short-acting insulin and then be managed by a CII. Diabetes diagnosed in the perioperative period is best managed with insulin delivered as a CII. Treatment with insulin should commence when the blood sugar is greater than 10 mmol/L.
During surgery the blood glucose levels should be monitored half hourly when the patient is being managed with insulin therapy and hourly in those patients not managed with insulin therapy. Intra-operative blood glucose levels should be maintained between 4 and 10 mmol/L and treatment should begin with insulin when the blood glucose level is above 10 mmol/L. The signs of hypoglycaemia are masked in the anaesthetised or sedated patient and hence close monitoring of blood glucose levels is essential. If the blood glucose level falls below 3.5 mmol/L the CII is ceased and a bolus of 50 ml of 50% dextrose should be administered.
Postoperative patients should be maintained on the CII for 48 hours or until eating adequately to maintain the blood glucose levels between 4 and 10 mmol/L. Ongoing glycaemic management is based upon the patient’s preoperative management and glycaemic control as determined by the preoperative HbA1c. Aim for a blood glucose level less than 7mmol/L pre-breakfast and less than 10 mmol/L pre-lunch and dinner. Metformin should be recommenced when there is no evidence of uncontrolled heart failure, sepsis or significant renal impairment and only when the patient is eating. Other oral hypoglycaemic agents can be recommenced when the patient is eating. Patients who were managed preoperatively with insulin therapy should be recommenced on subcutaneous insulin.
In patients with uncontrolled diabetes, diabetic acidosis or coma, the attendant disorders of fluid and electrolytes should be corrected and any sepsis controlled rapidly. Acute surgical conditions may precipitate the development of severe diabetic acidosis and coma; often these conditions need early surgery combined with diabetic control. The diagnosis of diabetic acidosis is confirmed by urine examination and by measurement of serum glucose. Treatment is commenced with isotonic saline infusion. A bolus of insulin and subsequent CII are given, depending upon the degree of ketosis and the age of the patient. Further insulin is given according to the frequent blood glucose determinations. Potassium depletion is common and acid–base disorders may require correction. Monitoring of central venous pressure, plasma osmolality and body weight is often helpful.
A diabetic patient who is unconscious or disorientated is more likely to be hypoglycaemic than hyperglycaemic. Blood sugar estimation will give the diagnosis and insulin should never be given to an unconscious patient unless there is proof of hyperglycaemia. It is safer when in doubt to give 50 mL of 50% dextrose intravenously. This will restore consciousness promptly if there is hypoglycaemia, unless the patient has already suffered serious brain damage or has a concomitant cerebral disorder such as portal-systemic encephalopathy.
10.11 Mental health problems
Organic diseases commonly present with or have associated with them, psychological symptoms and concerns. Symptoms of anxiety are a normal concomitant of any surgical (or medical) condition.
Less immediately apparent is the fact that somatic symptoms are often the first presentation of psychiatric disorders. Physical diseases are respectable, but many patients and some doctors consider that mental health disorders are not. Therefore, patients often present to doctors with somatic symptoms that are used as tickets of entry when their primary disorders are emotional and behavioural. Depressed and anxious patients often present in this way, concentrating on a physical symptom such as weight loss (Ch 7.13) or bodily discomfort rather than the basic depression or anxiety state. If the doctor fails to recognise the underlying psychiatric basis of the presenting symptoms, a fruitless and potentially endless series of investigations may be embarked on in an attempt to find an organic basis for increasingly vague symptoms. Alternatively, the doctor must avoid becoming angry with the patient for what is taken to be evasiveness and failure to cooperate. Discernment, tact and empathy are required from the doctor in coming to the correct diagnosis. Some of the commoner problems encountered are discussed below and their management will often require professional assistance to resolve.
Clinical states
Anxiety disorders
Anxiety, apprehension and fear are normal concomitants of potentially serious surgical and medical conditions. This should be acknowledged and if severe managed with appropriate consultation. Physiological expressions of anxiety associated with increased sympathetic activity (increased heart rate, dry mouth, sweating and vasomotor changes, tremor, epigastric queasiness, hyperventilation and disturbed breathing) often accompany the presenting symptoms of organic illness.
In anxiety disorders, the anxious affect and mood are sustained despite absence of real threat. Anxiety syndromes may produce unformulated apprehension, gross motor restlessness (agitation) and panic attacks. Chronic symptoms consist of feelings of impending doom and accompanying powerlessness to prevent this, inability to perceive the unreality of the threat, persistent high tension and exhaustive readiness. Somatic symptoms are common. They include band-like headache, muscle aches and pains, palpitations, tremor, epigastric discomfort, belching, tingling and cramps in the legs and hands due to hyperventilation, sweating, and urinary and sexual dysfunctions. Depersonalisation (the feeling of being an impotent spectator of one’s own actions) is common. Inability to sleep and fear of travelling or going out alone can also occur. The symptoms may occur acutely, as in panic disorder, or chronically as in generalised anxiety disorder and posttraumatic stress disorder.
Depressive disorders
Depressed patients often present with physical symptoms such as headache, generalised aches and pain, weight loss, loss of appetite and malaise. The depressed mood and affect of the patient may be obvious. Depression is usually associated with loss of pleasure and slowness of thought, speech and motor activity. However, many depressed patients are also agitated and anxious, which tends to mask the underlying depression and many depressed patients will initially hide or deny this depression. The clinician should be alert to somatic symptoms commonly associated with depression: anorexia, loss of energy, constipation, weight loss and insomnia. Careful enquiry may reveal associated depressive symptoms of loss of interest, inability to concentrate, loss of self-esteem, sadness and loneliness, feelings of guilt, self-reproach and withdrawal and at times a desire to die. Depressive symptoms are often worse in the morning and associated with insomnia and early wakening. They tend to improve during the day and to return in the evening. Suicide is an important and preventable risk in depressed patients. In some cases there may be no obvious cause for depression, but organic illness itself may be a precipitant, both physically and psychologically.
Grief also produces an alteration of mood and affect, but in this instance consisting of sadness appropriate to a real loss. It is important to take a complete social and family history in such instances to identify recent grief-inducing events. Loss of health or function of bodily parts is usually followed by a grief reaction.
Mania and hypomania are states of excessive excitability, elated but unstable mood, agitation and motor and speech hyperactivity. They are seen in the manic phase of bipolar illness. Associated features include impatience, intolerance, disregard of the feelings of others and a bland indifference of practical difficulties. This has considerable implications for management issues such as compliance with treatment.
Somatoform disorders
Somatisation of mental states occurs also in the absence of significant anxiety or depression. There may be a general preoccupation with the fear of having, or the belief that one has, a serious disease, based on the person’s interpretation of physical signs or sensations as evidence of physical illness. This is hypochondriasis. In hysterical conversion disorder, acute or chronic, there is a loss or alteration in physical functioning suggesting a physical disorder; however, the absence of sufficient physical cause, the manner of presentation and the identification of a relevant psychosocial stressor usually permit the correct diagnosis to be made. Somatoform pain disorder is a special example. A point often overlooked is that hysterical conversion, including pain, often accompanies a physical disorder. Indeed, the fact of developing the physical disorder may constitute the necessary psychosocial stressor, as in compensation neurosis. Munchausen’s syndrome is an extreme example of chronic somatoform disorder. The patient presents (often under a variety of aliases and to several institutions) with a dramatically and plausibly fabricated clinical story suggesting the need for urgent surgery or powerful narcotics.
Somatoform disorders are to be distinguished from psychosomatic (psychophysiological) disorders, in which a physical disorder is present, but a psychological factor is considered to be an important precipitating or maintaining factor.
Organic mental syndromes
Confusion
Confusion or muddled thinking is a cardinal symptom of organic mental syndromes, though it may occur in nonorganic conditions also. There is difficulty in attention and decreased cognitive (thinking) function. Disordered orientation in time, place or person is often present. Confusion may be obvious or apparent only on careful enquiry. Confusion may be acute or chronic.
Delirium
Delirium (acute brain syndrome) is an acute confusional state associated with acute impairment of consciousness. Disorientation, restlessness, agitation, illusions and hallucinations and impaired motor and autonomic activity are common.
Delirium is suspected if the patient has fluctuating attention during history-taking or has difficult in recounting the history coherently. Confusion may be precipitated, particularly in elderly patients, by the change from a familiar home environment with a fixed daily routine to the unfamiliar and disturbing environment of the hospital ward. Confusion is often worse at night.
Common causes of delirium in hospitalised surgical patients include:
• hypoxia — common in postoperative and sedated patients and those with atelectasis
• sepsis — chest, wound and urinary infections are the most common
• drug intoxication or withdrawal — common drug intoxications are from sedatives, analgesics and opiates and from withdrawal of alcohol
• metabolic disorders — water and electrolyte disturbances (hyponatraemia, hypernatraemia), hypoglycaemia or hyperglycaemia, anaemia, uraemia, hyperthyroidism or hypothyroidism, hepatic disease.
Vulnerability to the above produced by underlying CNS disorders (Alzheimer’s and Pick’s disease, cerebral vascular disease or tumour).
Confusion without impairment of consciousness may be due to psychiatric disorders such as anxiety, depression and psychosis.
Dementia
This is the most severe of the organic mental syndromes and is often associated with irreversible and permanent loss of intellectual processes, as distinct from the distortion of function occurring in delirium. The main differentiating features are the clinical pattern of each.
Early stages of dementia involve subtle changes noticeable only by relatives or friends. Worsening dementia involves progressive impairment of memory orientation, cognitive intellectual activities of comprehension and knowledge, judgement, mood and affect.
Orientation is most affected in regard to person and place. Recent memory is affected more than memory of remote past events. Intellectual ability is diffusely impaired, with decline in comprehension, calculation, general knowledge and learning abilities. Loss in creative activity occurs with lack of interest and initiative. Lapses in social behaviour can later become obvious and inappropriate and distressing to relatives. Judgement is impaired to a variable degree. Impairment of insight and judgement often complicate and worsen family relationships. Changes in internal mood and external affect may occur — the patient may be depressed. More commonly, a labile elevation of mood occurs with inappropriateness and shallowness of affect. The patient’s appearance and dress may become untidy and uncared for.
Causes of dementia
• Degenerative disorders (Alzheimer’s disease, Pick’s disease, Parkinsonism, Wilson’s disease, Friedrich’s ataxia, Huntington’s chorea, Creutzfeldt-Jakob disease). These syndromes cause insidious and progressive dementia commencing in the fifth decade and include the most common dementias.
• Vascular disease (multi-infarct dementia). This is the other common dementia. Arterial disease is usually evident at other sites.
• Alcoholic dementias. Nutritional deficiencies associated with alcohol produce Korsakov’s psychosis with impaired recent memory and confabulation. Wernicke’s encephalopathy may also be present and causes double vision due to ophthalmoplegia, together with sensory neuropathy.
• Drugs. Apart from alcohol, other drugs of addiction are common causes of dementia.
• Cerebral tumours, particularly of the frontal cortex.
• Metabolic disorders such as those producing delirium and nutritional deficiencies, such as pellagra (niacin), pernicious anaemia (B12), beriberi (thiamine).
• Posttraumatic dementia can follow severe head injury.
• Neurosyphilis is now a rare cause of dementia and AIDS an increasingly common one; dementia can be the primary presentation.
Drug dependence and abuse
In modern society an increasing proportion of patients with surgical problems will be found to be drug dependent or addicted. Drug abuse and addiction are often related to or contributory to the underlying problem or disease. Diagnosis of drug abuse is accordingly very important when planning treatment. Drug dependence is also important in terms of withdrawal symptoms developing while in hospital. Because the patient’s life style is usually intimately geared to the drug dependence and usually represents a method of coping with stress, the history of drug abuse is often concealed from the doctor. A history obtained from relatives or friends is often necessary to corroborate the clinician’s suspicions. The drug abuse may involve unlawful drugs of addiction and evasiveness of the patient may be related to this.
Common drugs involved are:
• alcohol
• narcotics
• sedatives.
Common related illnesses or problems are:
• alcoholic liver disease or psychosis
• tuberculosis and other bacterial infections
• hepatitis B or C, HIV/AIDS.
Drug dependence often interferes with work, family life, health and social behaviour. Alcoholism is suspected by frequent hangovers and failure of memory during and after drinking binges, by previous episodes of delirium tremens (DTs), by morning nausea causing breakfast to be missed and by a history of starting drinking early in the day.
Diagnostic and treatment plans
Anxiety neuroses and depressive states of psychological origin need to be distinguished as rapidly as possible from organic disease states (e.g. thyrotoxicosis or cancer). It is important to exclude organic disease by appropriate investigations so that the patient can be reassured of their absence. It is even more important to avoid fruitless over-investigation of somatic symptoms when major psychological problems are clearly present. Somatic disorders in which chronic psychological symptoms can be marked include hyperthyroidism and myxoedema, hyperparathyroidism and cerebral tumours. While management of psychological components of illness requires a broad, biopsychosocial approach, of particular relevance to the management of surgical conditions is knowledge of drug therapy.
Drug therapy of psychological problems is often effective but side effects must be carefully monitored. It is important for the surgeon to know the patient’s current medication in preparation for elective or emergency surgery.
Anxiolytics, sedatives and hynotics
These agents produce sedation and reduce anxiety. They are habit-forming and tolerance-inducing.
Benzodiazepines. Diazepam, oxazepam, bromazepam, lorazepam and other related drugs are very widely used as so-called minor tranquilisers or anxiolytics. Others (temazepam, nitrazepam and flunitrazepam) are used as hypnotics. Overdosage can cause drowsiness, ataxia, confusion and stupor. Effects are potentiated by alcohol, barbiturates and other sedatives.
Antipsychotics
These are used to reduce psychomotor activity in organic and functional psychoses. They often cause extrapyramidal side effects of Parkinsonism, dystonia and akathisia. The major groups of first-generationantipsychotic agents are the phenothiazines: chlorpromazine and its numerous derivatives (e.g. prochlorperazine, trifluoperazine, thioridazine, fluphenazine), the butyrophenones such as haloperidol and the thioxanthines such as chlorprothixene and flupenthixol. Commonly prescribed second-generation antipsychotic agents include clozapine, olanzapine, risperidone, quetiapine and ziprasidone.
Antidepressant drugs
Tricyclic antidepressants (dibenzazepines). Imipramine, amitriptyline, doxepin and derived agents are similar to phenothiazines in structure and have sedative and antidepressant effects. They all block the neuronal uptake of noradrenaline and all show anticholinergic properties.
Tetracyclic antidepressants. Mianserin is used because it is less cardiotoxic and has fewer anticholinergic effects than the tricyclics.
Selective serotonin reuptake inhibitors (SSRIs). Fluoxetine, paroxetine, sertraline and citalopram slow the breakdown of serotonin and enhance cerebral serotonin activity. They take two to three weeks to act and may result in drowsiness, dry mouth, loss of libido, constipation and dizziness.
Serotonin and noradrenaline reuptake inhibitors (SNRIs). Venlafaxine and nefazadone slow the reuptake of serotonin and noradrenaline. Side effects include drowsiness, intense dreaming and abdominal symptoms.
Monoamine oxidase inhibitors. Tranylcypromine and phenelzine, by inhibiting the enzyme monoamine oxidase, increase the concentration of adrenaline, noradrenaline and 5-hydroxytryptamine in the body. Their actions are slow in onset and offset. These drugs are less commonly used now because of their liability to invoke hypertensive crises by potentiation of sympathomimetic agents, including foods with high concentrations of tyramine (cheese, alcohol).
Phenothiazines. These agents are used in combined therapies for depression with schizophreniform features.
Lithium carbonate. This antimanic agent is used alone or in combination with antidepressants in treatment of bipolar syndromes.
10.12 Additional preoperative preparation
Additional preoperative preparation must attend to certain factors that are specific for individual operations and diseases (Boxes 10.18-10.24). Patients with ASA classes 3 to 5 will require baseline tests for appropriate systemic disorders.
Box 10.18A
Preoperative preparation: oesophageal surgery
Improve oral hygiene and control dental sepsis.
Chest physiotherapy and antibiotics for chronic bronchitis or aspiration pneumonitis.
Correct anaemia and malnutrition. Consider preoperative enteral or parenteral feeding.
Prophylactic antibiotics to prevent wound sepsis.
Box 10.18B
Preoperative preparation: gastroduodenal surgery
Correct associated problems of anaemia, metabolic alkalosis and hypokalaemia, and malnutrition.
Prophylactic antibiotics (including anti-anaerobes) in patients on H2 receptor antagonists or with gastric ulcer/cancer and gastric outlet obstruction.
Preoperative gastric lavage for pyloric stenosis.
Chest physiotherapy to control obstructive airways disease.
Preoperative proton pump inhibitors to control painful ulceration.
Box 10.19A
Preoperative preparation: chronic liver disease
Prevent or control encephalopathy by emptying the gut of protein and altering the gut flora.
Support liver function with vitamins C, B (especially thiamine) and K and intravenous hypertonic glucose infusion.
Correct anaemia, hypokalaemia and hydrogen ion disorders.
Prevent deterioration in lung function — chest physiotherapy, antibiotics, careful attention to fluid balance.
Prompt control of haemorrhage in patients bleeding from varices by a combination of balloon tamponade and sclerotherapy.
Monitor and maintain urine volume using thiazide diuretics, aldosterone antagonists (with ascites) and inotropic support of cardiac function.
Box 10.19B
Preoperative preparation: jaundiced patient
Prevent renal injury by perioperative hydration and maintaining an adequate urine output.
Prevent sepsis by prophylactic antibiotics.
Minimise bleeding risk: routine treatment with parenteral vitamin K, regular check of coagulation profile.
Control prolonged hyperbilirubinaemia and cholangitis by preliminary ERCP drainage of the biliary tree by sphincterotomy and/or nasobiliary drainage.
Box 10.20
Preoperative preparation: colorectal surgery
Diagnose and correct anaemia and hypokalaemia.
Prevent sepsis by prophylactic antibiotics and mechanical bowel preparation.
Preoperative colonoscopy to exclude synchronous cancer and to remove adenomas.
Assess selected cases for ureteric or duodenal involvement by IVP for left-sided and CT scan for right-sided lesions.
Prepare the patient for the possibility or certainty of a stoma.
Box 10.21
Preoperative preparation: urological surgery
Indwelling catheter or suprapubic cystostomy to relieve obstruction.
Control urinary tract infection.
Restore renal function by correcting prerenal factors such as volume depletion, electrolyte and hydrogen ion abnormalities.
Avoid nephrotoxic antibiotics.
Maintain hydration and diuresis during surgery.
Box 10.22
Preoperative preparation: vascular surgery
Perioperative hydration to reduce the risk of prerenal injury secondary to intra-operative hypotension.
Prophylactic antibiotics and careful skin preparation, especially in the patient with ischaemia.
Control sepsis in leg ulcers before surgery.
Control diabetes mellitus.
Box 10.23
Preoperative preparation: thyroid surgery
Ensure the patient is euthyroid on antithyroid medication.
Indirect laryngoscopy to check vocal cord movement.
Serum calcium and TFTs as preoperative baseline tests.
Image the neck and thoracic inlet to exclude tracheal compression by intrathoracic goitre.
Box 10.24
Preoperative preparation: hernia surgery
Control chronic obstructive airways disease. Stop smoking at least one month before surgery. Chest physiotherapy.
Consider transurethral resection of the prostate before hernia repair in patients with severe prostatism.
Control constipation if present.
1 Goldman L 1983 Cardiac risks and complications of noncardiac surgery. Ann Intern Med;98:504–513.