Saturday 11th August 2007
A new report published by Australian researchers in the journal Anaesthesiology claims that the anaesthetic gas administered to millions of patients for performing operations increases the risk of post-operative complications including heart attacks.
Nitrous oxide ?? also called laughing gas on account of the euphoria it leaves in people who inhale it ?? is the most commonly used anaesthetic for operations. Millions of patients across the world who go under the knife are administered the gas. Nearly 50% of all operations are carried out with this anaesthetic.
The researchers from Alfred Hospital in Melbourne looked at more than 2,000 patients all of whom had undergone an operation of some kind. The researchers found that patients who were administered nitrous oxide were much more likely to suffer severe side-effects in the month following their operation than those sedated with an oxygen-based mixture.
They found that patients receiving nitrous oxide had twice the risk of developing severe nausea or vomiting after coming round than patients who were not given the gas. Such patients were also at twice the risk of developing pneumonia.
They also developed more wound infections; their risk of developing a fever was also that much higher. The patients were also found to be three times more likely to suffer a heart attack and five times more likely to have died in the month after surgery.
Based on their findings, the researchers urged doctors to take care about using nitrous oxide in major operations to avoid the risk of after-effects. In their opinion, major operations are those that last more than two hours and include procedures such as brain surgery and major spinal surgery.
They said, ??Major post-operative complications were significantly reduced if nitrous oxide was avoided. The decreased risk of complications in the nitrous oxide-free group could be explained by the avoidance of nitrous oxide and/or administration of high oxygen concentrations.?
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At the same time, the researchers did not rule out the possibility of higher incidence of heart attacks and deaths in the nitrous oxide group being purely chance. The reason for their being cautious is the overall low number of heart attacks and deaths. They could neither establish a clear link between healthier patients and their not having the gas nor conclude that using more oxygen in the mix resulted in health benefits.
??We believe that, in a practical sense, this distinction is immaterial; regardless of whether the risk reduction is a result of nitrous oxide toxicity or direct effects of supplemental oxygen, anaesthesiologists should question the inclusion of nitrous oxide as part of their anaesthetic regimen,? they said.
??The routine use of nitrous oxide in adult patients undergoing major surgery should be questioned." In their opinion, even the smallest of links between nitrous oxide use and heart attacks is extremely important and should be strongly established. As a result, they have started a second study to further confirm their findings.
Clarifying their findings, they stressed that the patients covered in the study were all adults undergoing major surgery. As a result, they would have been administered large amounts of nitrous oxide. They therefore opine that their findings do not necessary apply to comparatively smaller operations that last less than two hours.
Alan Merry, Chairman of the Australian College of Anaesthetists said, ??The evidence is sufficiently compelling to convince me to change my practice.? Despite the findings, other anaesthetists continue to support the use of nitrous oxide on account of its valuable pain relieving properties.
David Bogod, of the Association of Anaesthetists, said British doctors have been gradually switching to more modern alternatives. ??Every drug used by every doctor has beneficial effects and adverse effects. But this is another nail in the coffin for the use of nitrous oxide in major surgery,? he said.
