7. PERIOPERATIVE BETA BLOCKADE

Previous controlled studies with nitrates, calcium channel blockers, clonidine and digoxin have not demonstrated protection from myocardial ischaemia intra- or postoperatively.

Recent studies suggest that giving beta-blockers perioperatively may reduce the risk of cardiac complications and death in patients having major non-cardiac surgery. The greatest benefit would seem to be for those patients at high risk of perioperative cardiac complications having major surgery.

Contraindications

Beta-blockade should not be used in patients who have a resting heart rate less than 60 beats/minute or who have asthma requiring regular treatment.

Choice of Beta-blocker

If possible, beta-1 selective beta-blockers should be used. Non-selective beta-blockers are more likely to produce respiratory complications such as bronchospasm.

At this stage no evidence suggests any particular beta-1 blocker is better.

Management

The beta-blocker should be started as soon as possible before the surgery in high-risk patients (even up to a month before) so that the dose can be changed to achieve a resting heart rate of 50 to 60 beats/minute. Even if the anaesthetist is unable to start beta blockade in the weeks before surgery, there may still be a benefit in giving a beta-blocker on induction of anaesthesia. The beta-blocker should be given in small doses to avoid a fall in blood pressure of greater than 20%.

The beta-blocker should be continued after surgery at least as long as the patient remains in hospital.

High Risk Factors

Patient risk factors for perioperative myocardial infarction include:

previous myocardial infarction or angina,

diabetes,

major surgery (intraabdominal, intrathoracic, vascular),

congestive heart failure,

renal impairment due to vascular disease or diabetes and

poor exercise tolerance (unable to walk up 2 flights of stairs or 400 metres on flat ground).

Recommendation

Giving beta-blockers perioperatively may reduce the risk of cardiac complications and death in patients having major non-cardiac surgery.

High-risk patients are those with 3 or more of the above risk factors or myocardial infarction within the previous 6 months or angina increasing in severity or of recent onset. A cardiologist should review them before surgery.

Low to moderate risk patients have only 1 or 2 of the above risk factors present and should be treated with beta-blockers at least one week before major surgery aiming for a resting heart rate of less than 60 bpm.