Anaesthetic switch 'may cut risk'

Nitrous oxide is often used as an anaesthetic during surgery

A gas commonly used in anaesthetics might not be safe as many people think, Australian scientists have warned.

In a study of over 2,000 people, they found avoiding using nitrous oxide cut the risk of surgery complications like wound infections.

The research, in Anesthesiology, also found a possible link between nitrous oxide and the risk of heart attacks.

But experts have warned that in many cases the use of nitrous oxide remains safe and has other advantages.

Some people argue that it is unlikely that all the benefits are due to the elimination of nitrous oxide, but in practical terms, who cares? Professor Paul Myles

In the UK, around 6 million anaesthetics are given every year, and a significant proportion of these include nitrous oxide.

The gas is included in the mixture which patients breathe during surgery, as a supplement to the anaesthetic drugs used.

Improved outcomes

Some evidence suggesting potential side-effects from nitrous oxide use already existed, but in the latest study, the first on such a large-scale, the researchers looked at the outcomes of operations performed in 19 hospitals around the World, including in the UK.

They compared the effects of using a mixture of 70% nitrous oxide and 30% oxygen as part of the anaesthetic cocktail, with an alternative mixture of approximately 80% oxygen and 20% nitrogen.

They found patients given the oxygen-nitrogen mix suffered half as many cases of severe nausea and vomiting, and on average a 30% reduction in serious complications such as wound infections and pneumonia.

They also found patients recovered from their anaesthetics just as well as those given nitrous oxide.

Lead researcher Professor Paul Myles, from the Alfred Hospital in Melbourne, Australia, said nitrous oxide could interfere with the metabolism of some vitamins, and with DNA synthesis, which is important in wound healing.

Serious implications

The study also found there could be a link between nitrous oxide and heart attacks after surgery, but this effect was too small to be confirmed, and is now being investigated in more detail.

With the publication of this article, the use of nitrous oxide will undoubtedly diminish Dr Keith Myerson

Harriet Hopf, of the University of Utah, said in an editorial article: "This study is not the last word on nitrous oxide, but it is an important one that is likely to have a major impact on clinical practice in anaesthesia."

But other experts have warned that the use of nitrous oxide in certain cases, such as many operations on children, women in labour, and minor surgery, could still be appropriate - mainly because the gas itself can help to kill pain, and is fast-acting.

Dr Keith Myerson, a member of the Royal College of Anaesthesiologists, said: "The Australian study suggests that there may be benefits in eliminating the use of nitrous oxide in patients having major surgery.

"With the publication of this article, the use of nitrous oxide will undoubtedly diminish.

"However, it is not clear from the study whether or not the benefits were due to the elimination of nitrous oxide or the use of high concentrations of oxygen."

But he added that more work was needed to pin down the exact effect of high concentrations of oxygen administered during anaesthesia.