Patients taking blood pressure drugs known as beta blockers had double the risk of heart attack after surgery and more than double the risk of dying within a month of the operation, US researchers said on Monday.

Beta blockers are often given to slow a patient's heart rate before routine operations such a hernia repair, but recent studies are beginning to suggest the drugs may do more harm than good.

"This study very clearly shows you have to be very cautious about it. It's not for everybody," said Dr. Kamal Itani of Boston University, whose study appears in the Archives of Surgery.

Itani said surgeons embraced the use of beta blockers after major studies in the 1980s suggested the drugs reduced heart risks in people undergoing surgery.

But Itani thinks there was not enough evidence to show the risks outweighed the benefits. "It was a very hasty decision," he said in a telephone interview.

Now, evidence is beginning to suggest the drugs can actually raise the risk of heart problems and death.

In May, a team led by Dr. P.J. Devereaux of McMaster University in Ontario, Canada, reported in the journal Lancet that people who got a high dose of a beta blocker before surgery were a third more likely to die and had double the risk of stroke compared with those given a dummy pill.

For his study, Itani and colleagues looked back at the medical records of 238 patients who were on beta blockers for heart conditions anyway before surgery in 2000 and a carefully matched group of 408 patients who were not on the drugs.

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