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:

Procedure-related risk factors may be anaesthesia-related or operation-related and vary with:

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.

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.

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.

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.