The results of new research has shown that patients given high doses of beta blocker drugs following non-cardiac surgery were more likely to have a stroke or die. However they were less likely to suffer a heart attack.
Beta blockers are drugs which decrease the force and rate of the heart's contractions, which lowers blood pressure and reduces the heart's demand for oxygen.
Worldwide, about 100 million adults undergo non-cardiac surgery every year to treat a range of conditions which affects how well the heart functions such as atherosclerotic disease (hardening of the arteries), coronary artery bypass graft (CABG) surgery or angioplasty, atrial fibrillation, a type of irregular heartbeat, hypotension, low blood pressure that requires medical treatment and bardycardia, a low heart rate that needs medical treatment.
One million of such patients will suffer major complications associated with the surgery which results in an increase in heart-rate, blood pressure, and fatty acid concentrations, which in turn increases the oxygen demands made on the heart.
Beta blockers are thought to help reduce such effects and prevent cardiovascular complications, however previous research on this theory has produced mixed results.
An international trial led by Canadian researchers involving 8,351 patients set out to test the theory.
All the patients either had or were at risk of atherosclerotic disease and were about to undergo non-cardiac surgery; 4,174 patients were randomly chosen to receive a beta blocker metoprolol succinate and 4,177 were given a placebo.
Dr P. J. Devereaux, from McMaster University in Hamilton and his colleagues conducted the POISE (PeriOperative ISchemic Evaluation) study to investigate the effects of peri-operative beta blockers.
The study was done in 190 hospitals across 23 countries including the UK, Australia, Canada, New Zealand, Argentina, Hong Kong, Malaysia, Singapore, Brazil, China, Colombia, Ecuador, Finland, Hungary, India, Mexico, Norway, Peru, Spain, Sweden, Thailand, Cuba, El Salvador.