Using nitrous oxide for anesthesia doesn't increase — and may decrease — complications and death
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, according to a pair of studies in the May issue of Anesthesia & Analgesia, official journal of the International Anesthesia Research Society (IARS).
But an accompanying series of editorials points out some important limitations of the two studies—which can't completely overcome previous concerns about the safety of using nitrous oxide (N2O) as a surgical anesthetic.
Is Nitrous Oxide Safe for Surgical Anesthesia?
Nitrous oxide is the world's oldest general anesthetic, but there's a long history of debate regarding its appropriate role in modern surgical anesthesia. Although nitrous oxide provides effective sedation and pain control, it has known disadvantages and side effects. A previous study, called “ENIGMA-I,” reported a small but significant increase in myocardial infarction (heart attack) among patients receiving nitrous oxide as part of anesthesia for noncardiac surgery (procedures other than heart surgery).
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.
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 trials—the 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 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.
About the IARS
The International Anesthesia Research Society is a nonpolitical, not-for-profit medical society founded in 1922 to advance and support scientific research and education related to anesthesia, and to improve patient care through basic research. The IARS contributes nearly $1 million annually to fund anesthesia research; provides a forum for anesthesiology leaders to share information and ideas; maintains a worldwide membership of more than 15,000 physicians, physician residents, and others with doctoral degrees, as well as health professionals in anesthesia related practice; sponsors the SmartTots initiative in partnership with the FDA; and publishes the monthly journal Anesthesia & Analgesia in print and online.
About Anesthesia & Analgesia
Anesthesia & Analgesia was founded in 1922 and was issued bi-monthly until 1980, when it became a monthly publication. A&A is the leading journal for anesthesia clinicians and researchers and includes more than 500 articles annually in all areas related to anesthesia and analgesia, such as cardiovascular anesthesiology, patient safety, anesthetic pharmacology, and pain management. The journal is published on behalf of the IARS by Lippincott Williams & Wilkins (LWW), a division of Wolters Kluwer Health.
Alle Nachrichten aus der Kategorie: Health and Medicine
This subject area encompasses research and studies in the field of human medicine.
Among the wide-ranging list of topics covered here are anesthesiology, anatomy, surgery, human genetics, hygiene and environmental medicine, internal medicine, neurology, pharmacology, physiology, urology and dental medicine.
2020 Arctic sea ice minimum at second lowest on record
NASA and the National Snow and Ice Data Center (NSIDC) at the University of Colorado Boulder shows that the 2020 minimum extent, which was likely reached on Sept. 15, measured…
Dresden physicists develop printable organic transistors
Scientists at the Institute of Applied Physics at TU Dresden have come a step closer to the vision of a broad application of flexible, printable electronics. The team around Dr…
Researchers discover a mechanism that causes cell nuclei to grow
By far the most important process in cell development is how cells divide and then enlarge in order to multiply. A research team headed by Freiburg medical scientist Prof. Dr….