Preoperative assessment 1

Introduction 1

General preparation 2

Preoperative assessment of fitness for anaesthesia and surgery 3

Cardiovascular system 3

Respiratory system 5

Central nervous system 6

Renal system 7

Liver 7

Endocrine system 8

Haematology 9

Lifestyle influences on anaesthetic risk 10

Concurrent drug treatment 11

Prophylaxis of thromboembolic disease 13

Preadmission clinics 14

Routine investigations prior to surgery 14

Further reading 15


The preoperative evaluation of patients is intended to reduce the morbidity and mortality associated with surgery and anaesthesia. The relative benefits of the proposed operation need to be balanced against the possible adverse effects that may result from anaesthesia and surgery. The severity of any underlying medical conditions and their impact on physiological reserve must be assessed. Optimisation of the management of any underlying medical condition is undertaken. It is necessary to take a detailed history, examine the patient and obtain appropriate laboratory investigations to achieve these goals. A plan for anaesthesia, postoperative care and pain relief can then be constructed and this generally involves:

• informing patient of the proposed procedure;

• obtaining informed consent for proposed procedure, including any risks from not having the procedure;

• assessing pre-existing conditions and estimation of their impact on physiological reserve;

• planning the type of anaesthesia guided by the above information and patient preferences;

• planning postoperative management of any pre-existing conditions;

• planning analgesia.

The American Society of Anesthesiologists' (ASA) classification has found wide acceptance as a broad-based system for classifying the general fitness of patients for surgery and their predicted mortality (Table 1.1). Factors increasing the operative risk include:

• emergency versus elective operation;

• presence of associated illnesses (especially uncontrolled diabetes or heart failure);

• physiological reserve impaired;

obesity, malnutrition, immunosuppression and cancer;

• radiotherapy, steroid use.

Table 1.1. ASA classification of illness.

1 No organic, physiological, biochemical or psychiatric disturbance

2 Mild to moderate systemic disturbance which does not limit normal activities

3 Severe systemic disturbance which limits normal activities but is not incapacitating

4 Severe, life-threatening systemic disorders

5 Moribund with little chance of survival

6 Increasingly ASA 6, is used to designate an organ donor E 'E' placed after the number, indicates an emergency operation

General preparation


Consent is a very important process in the preoperative management of patients. It is much more than informing the patient of the risks of the procedure and should include discussion of:

• An explanation of the condition requiring surgery and why that surgical procedure is considered the best option.

• Other treatments that could be considered as well as the expected outcome without treatment.

• A description of what will be done at the time of the procedure (i.e. what will be removed, site of incision and reconstruction).

• The expected anaesthetic management (i.e. general anaesthesia versus regional anaesthesia and sedation).

• What to expect following the anaesthetic (i.e. drain tubes, central venous and urinary catheters, stomas, etc.).

• Expected long-term outcomes and implications of the procedure.

• Confirmation of the side and site of the procedure to avoid 'wrong site or side' procedures.

To aid patient education and consent many surgical colleges and societies produce patient information pamphlets for common procedures.

Discussion of the complications of surgery can be an exhaustive process if all possible problems are discussed. Some patients may require a further consultation for follow-up discussion. Many patients will require the presence of a professional interpreter for the consent process, with family used for translation only when an interpreter is not available. Each patient needs to be individually assessed as some complications may be of greater significance than for other patients, even if very uncommon or rare. The discussion of risk for a procedure should be based on a balance of the benefit of the operation against its complications. In this component of the consent there should be discussion of:

• Common risks of any procedure and plans to avoid them (i.e. the use of heparin to avoid deep venous thrombosis, the importance of postoperative mobilisation in preventing deep venous thrombosis and pulmonary atelectasis);

• Specific risks of the procedure;

• Anaesthetic consent.

The legal interpretation of the consent process often differs to the medical interpretation. The laws regarding the consent process differ in each country. Furthermore, the age a patient is able to give informed consent differs according to the country and social circumstances. Health care providers must acquaint themselves with the particular legal and consent protocols in their locality and health care facility. Some specific situations should be considered in detail:

• Emergency: When urgency or the patient's clinical state precludes the obtaining of a valid consent, life-saving treatment may commence. This decision must be documented.

• Under-age patients: Parents can consent for their children however the legal situation becomes increasingly complex

Table 1.2. Effect of age on physiological processes.

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