Pre-Operative Assessment - Examination and Tests

Every year more than 3 million operations are performed. It is common practice to perform routine testing on patients before they go to theatre. Commonly used investigations are discussed below.

General

A general systems examination must be done to pick up any abnormalities:

• CVS - heart murmur. With the exception of emergency surgery, patients should be haemodynamically stable and their vital signs normal before starting anaesthesia.
• RS - abnormal breath sounds
• GI - abdominal masses, previous scars
• Musculoskeletal - skeletal malformations such as kyphoscoliosis
• General - local skin infection

Airway assessment

How easy or difficult it will be to intubate a patient depends on the following points:

• Are they obese?
• Do they have a short neck and small mouth?
• To what extent can they open their mouth?
• Is there any soft tissue swelling at the back of the mouth or any limitations in neck flexion or extension?

The doctor should ask whether the result of the test is going to alter the patient's management. Ordering unnecessary tests is neither helpful nor cost effective.

Following reviews on the available evidence of the value of routine preoperative testing in healthy or asymptomatic adults,¹ NICE has produced full guidance on the subject.² It covers tests that are often carried out when a patient is scheduled for elective surgery. They may be performed by a variety of health professionals, in different settings. It makes recommendations on the circumstances in which the tests should be done, not done, or considered. Whether a certain test is recommended may depend on the patient's risk factors, or how serious the planned operation is.

Full blood count (FBC)

This will demonstrate anaemia. This increases the risk of intra-operative hypoxia or increased cardiac workload. There is also an increased risk of myocardial infarction (MI) or cerebrovascular event (CVE) and delayed healing. It is also useful as a baseline measure of haemoglobin if the proposed operation is expected to cause substantial blood loss.

Urea and electrolytes (U&E)

Detects underlying renal deficiency and possibility of developing acute renal failure (ARF) after major surgery. It may also influence the choice of drugs given within the anaesthetic.

Liver function tests (LFT)

Does the patient have any underlying malnutrition? This may affect the patient's ability to heal.

Calcium

Is there a suggestion of underlying malignancy?

Clotting

Clotting and platelet function is relevant for the many patients who take aspirin or warfarin. Also patients with known clotting disorders.

Group and save (or hold)

Anticipating that there may be a requirement for blood, but not routinely for this procedure, the patient's blood type is identified and held, pending a possible (later) request for units of blood or blood products.

Cross-match

A requirement for transfusion needs to be anticipated to avoid high demand/unavailable resource. The surgeon makes a prediction (in units of blood) for the procedure. That amount, typed specifically for that patient, is held in blood bank for 24 hours. The decision about whether to cross match serum or to order group and save should be judged on the current haematological status of the patient as well as the estimated blood loss.

Urinalysis

Urine dipstick or analysis is useful to detect undiagnosed diabetes or urinary tract infection.

Chest X-ray (CXR)

Rules out infection and prevents last minute delay in anaesthetic. It is also an aid to diagnosis if the patient has a poor response to general anaesthetic. It may also help plan for post-operative physiotherapy.
A CXR should only be requested by the anaesthetist for assessment, or if they felt the patient may need admission to ITU post-operatively. This may be the case in patients with rheumatoid arthritis, to assess instability of the cervical spine - almost 90% of patients have some degree of involvement.³ Also patients with ankylosing spondylitis can have a semifused spinal column and the anaesthetist should bear this in mind when extending the patient's neck during intubation.
The following types of surgery do require a CXR if not already performed as part of work-up:

• Abdominal, cardiac and thoracic and some oesophageal surgery
• Thyroidectomy or head and neck surgery
• Neurosurgery - because of prolonged nature of anaesthesia and need for post-op ITU
• Lymph node surgery

Royal College of Radiology guidelines state that a CXR is NOT universally routinely required, regardless of age.⁴

Spirometry

Spirometry tests are a good measure of pulmonary physiology and are useful in patients with obstructive or restrictive patterns of disease.

Electrocardiogram (ECG)

This will show any silent myocardial ischaemia or infarction. It is also a baseline to compare against possible post-op events. It also demonstrates arrhythmias.

Sickle cell testing

It is important to offer testing pre-operatively to identify risk before the anaesthetic - surgical or dental. This is important for ethnic groups who have a family history of homozygous sickle cell anaemia or sickle cell trait, particularly where there is no previous surgical history.
At risk groups include:

• African
• Caribbean
• Eastern Mediterranean
• Middle Eastern
• Asian

It has also been found in Cypriot people.
Appropriate counselling is important, so that the patient realises the implication of both positive and negative results and is able to give informed consent.

Pregnancy testing

The need to test depends on the risk to the fetus from the surgery and anaesthetic. These risks should be explained to the patient.
The woman should be asked sensitively if there is any possibility of pregnancy. If there is any doubt, a test should be done with the woman's consent.
Similar questioning should be carried out before a CXR.

The American Society of Anesthesiologists' (ASA) grades⁵

Recommendations on which pre-operative investigations are necessary are based on ASA Grade and level of surgery or specialty; there are special recommendations for neurosurgery and cardiac surgery. Any co-morbidity e.g. CVD, respiratory or renal are also taken into account.
e.g. Grade 1 Surgery

• Fit children (i.e. <16 years), who are ASA grade I require no preoperative testing.
• ASA grade 1 adults; consider ECG if >40yrs and U&E if >60yrs.
• ASA Grade 2 adults with cardiovascular disease require an ECG. Also consider:
  • CXR if >40yrs
  • FBC any age
  • U&E any age
  • Urinalysis

Grade 1

• Release of peripheral nerve entrapment at wrist
• Drainage of middle ear
• Tooth extraction

Grade 2

• Electroconvulsive therapy
• Partial excision of breast
• Extraction of lens
• Haemorrhoid operations
• Evacuation of retained products of conception

Grade 3

• Thyroidectomy
• Open operation on bladder
• Total mastectomy
• Vaginal repair or hysterectomy

Grade 4

• Operations on lung
• Excision of colon/stomach/rectum
• Kidney transplant
• Total hip replacement