Outcomes remained similar on "propensity score" analysisa 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 N2OBut '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.
The results suggested a significant reduction in the risk of death after surgery for patients receiving nitrous oxide: about one-third lower than in patients who did not receive nitrous oxide. There was also a significant 17 percent reduction in the combined rate of major complications and death.
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.
In one of three accompanying editorials, Thomas R. Vetter, MD, MPH, and Gerald McGwin, Jr, MS, PhD, of University of Alabama at Birmingham highlight some important limitations of the study data. They note that, although both studies were large, they were not randomized trialsthe strongest type of scientific evidence.
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
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