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.

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 (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 . 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 receiving nitrous oxide as part of anesthesia for noncardiac (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 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 .

More information: Read the article: "This Wonder-Working Gas" Read the article: Comparing Apples to Oranges: Just Say No to N2O? Read the article: Nitrous Oxide and Cardiovascular Outcome: Perspective from the POISE Trial Read the article: Association Between Nitrous Oxide and Postoperative Mortality and Morbidity After Noncardiac Surgery Read the article: Nitrous Oxide and Serious Morbidity and Mortality in the POISE Trial

add to favorites email to friend print save as pdf

Related Stories

Greenhouse gases from farmland underestimated

Apr 02, 2013

(Phys.org)—Changes in agricultural practices could reduce soil emissions of the greenhouse gas nitrous oxide and the atmospheric pollutant nitric oxide, according to a new study by scientists at the University of California, ...

Study: Unexpected microbes fighting harmful greenhouse gas

Nov 21, 2012

The environment has a more formidable opponent than carbon dioxide. Another greenhouse gas, nitrous oxide, is 300 times more potent and also destroys the ozone layer each time it is released into the atmosphere through agricultural ...

Nitrous oxide from ocean microbes

Dec 10, 2007

A large amount of the greenhouse gas nitrous oxide is produced by bacteria in the oxygen poor parts of the ocean using nitrites, Dr Mark Trimmer told journalists at a Science Media Centre press briefing today.

Can biochar help suppress greenhouse gases?

Apr 20, 2011

Nitrous oxide is a potent greenhouse gas and a precursor to compounds that contribute to the destruction of the ozone. Intensively managed, grazed pastures are responsible for an increase in nitrous oxide emissions from grazing ...

Recommended for you

What are the chances that your dad isn't your dad?

23 hours ago

How confident are you that the man you call dad is really your biological father? If you believe some of the most commonly-quoted figures, you could be forgiven for not being very confident at all. But how ...

New technology that is revealing the science of chewing

Apr 15, 2014

CSIRO's 3D mastication modelling, demonstrated for the first time in Melbourne today, is starting to provide researchers with new understanding of how to reduce salt, sugar and fat in food products, as well ...

After skin cancer, removable model replaces real ear

Apr 11, 2014

(HealthDay)—During his 10-year struggle with basal cell carcinoma, Henry Fiorentini emerged minus his right ear, and minus the hearing that goes with it. The good news: Today, the 56-year-old IT programmer ...

Italy scraps ban on donor-assisted reproduction

Apr 09, 2014

Italy's Constitutional Court on Wednesday struck down a Catholic Church-backed ban against assisted reproduction with sperm or egg donors that has forced thousands of sterile couples to seek help abroad.

User comments