Giving nitrous oxide as part of general anesthesia for noncardiac surgery doesn't increase the rate of complications and death—and might even decrease the risk of such events.

The two new studies, based on large patient databases, question the harmful effects of nitrous oxide. Dr Kate Leslie of Royal Melbourne Hospital, Australia, and colleagues analyzed data from a previous study of more than 8,300 patients undergoing surgery. That study was designed to assess the effects of giving one type of blood pressure drug (beta-blockers) during surgery, not the effects of nitrous oxide.
Dr Leslie and colleagues compared the risk of death or serious complications after surgery for patients who versus did not receive nitrous oxide as part of anesthesia. Twenty-nine percent of patients in the study received nitrous oxide.
The results showed comparable rates of adverse outcomes between groups. With or without nitrous oxide, the overall rate of death or serious complications was approximately seven percent, including about a six percent rate of myocardial infarction. Risk of death after surgery was about three percent in both groups.
Outcomes remained similar on "propensity score" analysis—a technique accounting for characteristics making patients more or less likely to receive nitrous oxide. Use of nitrous oxide varied widely between the different countries and hospitals participating in the study.
No Increase in Risks with N2O—But 'More Definitive' Studies Needed Dr Alparslan Turan of the Cleveland Clinic and colleagues outcomes reviewed more than 49,000 patients undergoing noncardiac surgery between 2005 and 2009. In this study, 45 percent of patients received nitrous oxide.
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Surprisingly, nitrous oxide was specifically associated with a 40 percent reduction in the risk of major lung- and breathing-related complications. However, the authors acknowledge the risk of "selection bias"—anesthesiologists may have avoided using nitrous oxide in patients at risk of lung problems. Again, the findings remained significant on propensity score analysis.
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Drs Vetter and McGwin emphasize that even sophisticated techniques like propensity score analysis can't account for all of the differences between groups that may have affected responses to nitrous oxide. They note that a randomized "ENIGMA-II" study is underway, and may provide "additional, perhaps more definitive insight" on the risks and potential benefits of using nitrous oxide as part of general anesthesia.
Source-Eurekalert