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frequently first detected on routine screening. Liver disease of sufficient severity to affect outcome from surgery will be detected clinically, and thus liver function tests are only indicated when clinically detectable disease is present. Routine biochemical testing is not indicated on asymptomatic patients <60 years of age.

Haematology

Routine haemoglobin estimation for clinically well patients undergoing minor surgery is unnecessary. For major surgery, haemoglobin estimation and 'group and save' is advised. The lowest level of haemoglobin at which elective surgery should not proceed has been strenuously debated with 7g/dl being the lowest acceptable level in most studies (when major blood loss is not anticipated). Coagulation screening should only be done when clinically indicated or when undetected coagu-lopathy would be a major problem, such as in neurosurgery and heart surgery. Sickle cell status should be determined in patients at risk.

Chest radiograph

The chest radiograph is the most frequently over prescribed preoperative investigations. In the absence of clinical indications, the yield from this test is low. A chest radiograph (Fig. 1.1) should be performed only to confirm a suspected pathological condition likely to affect outcome from surgery, such as:

• cardiomegaly;

• suspected pulmonary metastases and mediastinal masses;

• suspected tuberculosis;

• significant known lung disease such as pneumonia, pulmonary oedema or atelectasis;

• suspected thoracic pathology such as fractured ribs, pneumothorax or pleural fluid accumulation.

Figure 1.1. Chest radiograph showing an enlarged heart shadow.

ECGs

By contrast, the ECG often provides the initial information regarding several clinically 'silent' conditions which may impact adversely on the patient's perioperative outcome.

• myocardial infarction;

- atrial flutter or fibrillation,

- ventricular ectopic beats;

• left or right ventricular hypertrophy;

• conduction problems:

- arteriovenous block (1st, 2nd or 3rd degree),

- Wolff-Parkinson-White syndrome,

- atrial or ventricular ectopics,

- prolonged 'QT' interval.

An ECG should be performed on all patients with known cardiovascular disease and on all asymptomatic patients >40 years of age.

Cardiac function tests

Nuclear medicine scanning provides valuable information of myocardial reserve in symptomatic patients. However, it should be remembered when assessing 'at risk' patients, that the presenting condition (e.g. arthritis requiring hip replacement) may mask cardiac symptoms by limiting the patient's exertion. TTE (if available) may provide valuable additional information regarding valve function and contractility.

Pulmonary function tests

Spirometry should be performed on patients with dyspnoea on mild to moderate exertion.

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