Heart attack treatment warning

Research on heart attack treatment has cast doubt on the standard use of oxygen therapy, suggesting it may even harm some patients.

The treatment of heart attack patients has routinely included inhaling oxygen through a mask or through prongs in the nostrils.

However, a systematic review of three small trials, published by the international Cochrane Library, has found there is no evidence that oxygen therapy during a heart attack is beneficial - confirming the conclusions of earlier New Zealand research.

"Some evidence even suggests it may cause further damage," says the Cochrane report by British and Spanish researchers.

Of the 387 patients involved in the three trials, 14 died, 10 of whom had received oxygen therapy and four, air. However the numbers were so small the apparent disparity may just be chance rather than a statistically valid difference.

Nonetheless, one of the researchers, Professor Tom Quinn, of Surrey University in Britain, said: "Given the fact that this is such a widely used treatment, we think it is important that a large trial is conducted as soon as possible to make sure that giving oxygen is not causing any harm."

This mirrors the recommendation of Medical Research Institute of New Zealand director Professor Richard Beasley and his colleagues in 2007 that good-quality trials were urgently needed.

They concluded in a review published in the Journal of the Royal Society of Medicine that the use of oxygen by heart attack patients was out of step with key studies.

However, Professor Beasley said yesterday it appeared medical practice was changing to reflect the evidence. Guidelines published in the New Zealand Medical Journal had advised that oxygen should be given only to patients who had a low oxygen saturation level in the blood.

He was involved in a New Zealand-British trial over oxygen use in heart attack patients, the results of which were expected by the end of the year.

National Heart Foundation medical director Professor Norman Sharpe, a heart specialist, said yesterday increasing the oxygen saturation in the blood by administering inhaled oxygen was a rational therapy for a heart attack because the condition involved oxygen starvation in the heart.

Although the Cochrane findings were inconclusive, they were of concern.

"There is probably a very big psychological placebo element to oxygen for a number of conditions. I'm sure in general we overuse oxygen in hospital.

"I see oxygen overused on the wards in patients with respiratory conditions and generally having to wean them off oxygen."