Australian researchers have said that avoiding the use of nitrous oxide may cut the risk of surgery complications, such as wound infections, and have highlighted a possible link with an increased risk of heart attack. The study included 2,000 people and looked at the outcomes of operations in 19 hospitals around the world, including in the UK.
The study compared the effects of using a mixture of 70% nitrous oxide and 30% oxygen, with an alternative mixture of around 80% oxygen and 20% nitrogen. The researchers found that patients suffered half as many cases of sever nausea and vomiting and on average a 30% reduction in serious complications such as wound infections and pneumonia, when the mix with greater oxygen content was administered.
Lead researcher, Professor Paul Myles, from Alfred Hospital in Melbourne, Australia, said nitrous oxide could interfere with the metabolism of some vitamins and with DNS synthesis, important to wound healing. However, he added that the effects on heart attacks were too small to be confirmed and this is being further investigated.
The Royal College of Anaesthetists (RcoA) responded by highlighting the beneficial pain relieving properties of the gas, particularly in childbirth and in emergency medicine, but added that the side effects have been known for some time. The RcoA also pointed out that with the advent of newer anaesthetic drugs and techniques including total intravenous anaesthesia (TIVA), use of the drug in the UK is now declining, with a mixture of air and oxygen commonly used as a substitute.
Dr Keith Myerson, Member of RCoA Council, issued the following caution: “The Australian study suggests that there may be benefits in eliminating the use of nitrous oxide in patients having major surgery. 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. The possible beneficial effect of high concentrations of oxygen during and after anaesthesia on wound healing and infection is controversial, and must be separated from the known side effects of nitrous oxide. High concentrations of oxygen can sometimes be harmful, particularly in babies.”
He called for further studies to ensure that the higher concentrations of any alternative agents, used in place of nitrous oxide, are “as safe for patients as nitrous oxide has proved to be for over one hundred years.”
