Chapter 10 Preoperative medical problems in surgical patients

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.

• 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.

• 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

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.

Box 10.4

Common perioperative factors that precipitate cardiac decompensation