Anaesthetics - Preoperative patient management

Question 1

What is the NCEPOD classification of intervention?

Answer 1

This is one of the more common classification systems for the urgency of surgery. The anaesthetist has to make sure that the patient is made as well as possible prior to surgery. In immediate cases, there will be no time for this, as resuscitation takes place alongside surgery. These cases are rare, and there is often a few hours to reduce risk and improve outcome (e.g. vascular access, urinary catheter, nasogastric tube, i.v. fluids). With elective patients the goal is to optimise there current medical conditions (e.g. treatment of angina or hypertension). In some cases it may be appropriate to refer for surgery first (e.g. coronary revascularisation or carotid surgery prior to joint replacement for example)

Question 2

How can patients be counselled about the risk associated with their procedure?

Answer 2

It is not possible to give an exact figure, but there are two main areas to consider - (i) the patient, and (ii) the proposed surgery. Cardiac risk is a major area, as post operative cardiac risk is not uncommon and can carry a significant mortality:

1) Low risk (<1%) = minor orhtopaedics and urology, gynaecology, breast, dental
2) Medium risk (1-5%) = major orthopaedic surgery, abdominal, head and neck
3) High risk (>5%) = aortic, major vascular, peripheral vascular, intraperitoneal/ intrathoracic

Question 3

What patient factors are associated with cardiac risk during surgery?

Answer 3

Age
Cerebrovascular disease
Heart failure 
IHD
Insulin dependent diabetes 
Renal impairment or dialysis

Question 4

What are the ASA grades?

Answer 4

The American Society of Anaesthesiologists grading system is a general risk scoring system. There are 7 grades (I-VII). The most common types are ASA I-III. These are:

• Grade I = normal healthy patient
• Grade II = a patient with mild systemic disease (e.g. well controlled hypertension
• Grade III = a patient with severe systemic disease (e.g. controlled CHF, stable angina)

Question 5

What are important aspects of the preoperative history and examination of patients for surgery?

Answer 5

This occurs in pre assessment clinics before surgery. The general medical assessment include:

• cardiac disease
• respiratory disease
• GI disease
• renal disease
• CNS disease
• musculoskeletal disease
• endocrine disease
• medication
• tobacco, alcohol and recreational drugs

In addition there are a few areas specific to anaesthesia:
1) Airway - ask about cervical spine problems (e.g. previous surgery or AS), trauma or infection of the airway, previous scarring of the head and neck (e.g. radiotherapy) and TMJ dysfunction. All of these suggest problems with ET intubation. Examine for Malampatti grade

2) Past anaesthetic history - ask specifically about anaesthetic problems
3) Family history - malignant hyperthermia

Question 6

What preoperative tests should be arranged for patients prior to surgery?

Answer 6

Common tests - FBC, U&E, coagulation screen, ECG and CXR. The emphasis should be on targeting those with abnormalities, where either knowledge of the abnormality would change management (e.g. investigation or treatment of anaemia) or act as a baseline for likely changes (e.g. ECG and CXR for cardiothoracic surgery). There is very little value in screening healthy patients with a battery of tests. But urinalysis should be performed in all patients.

For patients at risk/ those underoing high risk operations (esp vascular), other tests include:

• LFTs
• ABG
• respiratory function tests
• cardiac echo and other imaging (including angiography) to assess left ventricular function, valve gradients and quantify ischaemic heart disease
• cervical spine x ray may be required in those with suspected cervical spine degeneration, surgery and trauma as neck mobility is a key determinant of ease of tracheal intubation.

Final aspect is testing physiological reserve - e.g. performance status or exercise testing

Question 7

What considerations should be given to preoperative medication?

Answer 7

Generally, ALL medication is continued perioperatively except:

• drugs that affect coagulation (warfarin, heparin, aspirin, clopidogrel)
• hypoglycaemics
• some hypotensive drugs - e.g. ACEi are stopped only on the day of surgery

For drugs that affect coagulation, the relative risk of stopping the drug (thromboembolism) or continuing (perioperative bleeding) has to be determined. In some cases, the drugs are omitted altogether, or the patient is transferred to a lower dose or therapeutic doses of LMWH. For insulin dependent diabetic patients, long acting insulin is generally discontinued and a sliding scale with short acting i.v. insulin is started.

Some drugs can be started in the preoperative period to reduce risk.

Question 8

Why is fasting important preoperatively?

Answer 8

No anaesthetic should be given (unless in an emergency) until the patient is fasted. This is to prevent both gastric acid and particulate matter entering the tracheobronchial tree, which can in the former case cause pneumonitis and in the latter case airway obstruction. Elective surgery should not proceed unless the patient has had >2 hours since clear fluids, >4 hours since milk and >6 hours since solid food.

However, there are patients in whom the stomach can never be guaranteed to be empty. These are:

• those that have used opioids
• hiatus hernia
• acute abdomen (any cause) and raised abdominal pressure
• gastrointestinal obstruction
• pregnancy (2nd and 3rd trimester)
• severe trauma

These patients are at increased risk of aspiration and require intubation to protect the airway.