Australian researchers are delighted with the outcome of a major international study that proves the safety of nitrous oxide, better known as happy gas.

This ends one of modern medicine’s great debates, says Professor Paul Myles, leader of a six-year international study known as ENIGMA-2.

Happy gas, or nitrous oxide, has been used millions of times over the past 160 years. But over the past five or ten years many anaesthetists have opted for more expensive alternatives because of several conflicting reports on patient safety.

The long-awaited ENIGMA-2 study is internationally regarded as the final word.

Announcing the results on Tuesday, Prof Myles was emphatic: “Patients are at no greater risk of complication when given nitrous oxide over another drug.

“The risk of heart attack, stroke or infection is very low and unaffected by the anaesthetic,” the Alfred Hospital anaesthetist told an Australian and New Zealand College of Anaesthetists (ANZCA) conference in Singapore.

The researchers studied the risk to 7000 seriously ill elderly patients in Australia, Asia, North America and Europe.

They are confident it is also safe for women in labour, children and dental patients.

“It’s crystal clear that it is safe to use in most circumstances,” said Prof Myles.

“Nitrous oxide is cheap and easy to use. These results are very reassuring, ” said Prof Myles.

“It is great news for anaesthetists and patients,” said co-researcher Professor Kate Leslie.

There has been a lot of concern about nitrous oxide but the study puts the matter to rest.

“It is a unique gas. It puts people to sleep but it also provides strong pain relief when you use it in lower doses,” said Prof Leslie, head of anaesthesia research at the Royal Melbourne Hospital.