‘Laugh’ Your Way Through Surgery

Nitrous oxide or laughing gas may not be associated with a higher risk of heart attacks

(RxWiki News) Nitrous oxide, better known as laughing gas, has been used as an anesthetic during surgery since the 19th century. Though it is widely used to this day, some studies linking it to a risk of heart attack have questioned its safety.

Anesthetics are used during surgery and other procedures to produce a loss of feeling.

According to a new study, it might be too early to dismiss laughing gas as an unsafe anesthetic.

Results of this study suggest that administering nitrous oxide as an anesthetic during surgery did not have a significant effect on the risk of heart attacks during and after surgery.

"Ask your surgeon about the safety of anesthetics."

This study was conducted by Peter Nagele, MD, assistant professor of anesthesiology and genetics at the Washington University School of Medicine, and colleagues.

The aim of the study was to find out whether nitrous oxide raised the risk of heart attack when used as an anesthetic during surgery.

Laughing gas inactivates vitamin B12 which, in turn, increases blood levels of the amino acid homocysteine. Homocysteine has been thought to raise the risk of heart attacks during and after surgery.

The researchers looked at 500 surgery patients who had non-heart surgery and were given nitrous oxide anesthesia. The patients had been diagnosed with coronary artery disease, cardiac failure or other health issues that are linked to the risk of having a heart attack.

Half of the patients received vitamin B injections and the other half did not receive these injections.

Vitamin B prevents homocysteine levels from increasing during surgery. But no significant differences in the rate of heart attacks were observed between the two groups, suggesting that the risk of heart attack was not influenced by homocysteine levels.

The researchers also monitored an enzyme called troponin I in the blood. Increase in troponin I levels are linked to heart muscle damage.

No link was found between homocysteine and troponin levels, suggesting that even if nitrous oxide raises homocysteine levels, this is not directly associated with heart damage.

The study also examined gene variations that are linked to elevated levels of homocysteine. When people with these variations get nitrous oxide anesthesia, their homocysteine levels increase a lot.

Only 3.1 percent of patients who had the risky gene variation had heart attacks during or after surgery, compared to 4.7 percent of those who did not have the variations.

Thus overall, the researchers concluded that neither the gene variation nor homocysteine levels had a significant effect on the risk of heart attack during or following surgery.

"People who had the gene variant did, indeed, develop very high levels of homocysteine in response to nitrous oxide. So the question is whether those patients would be at a higher risk for heart attack, and that answer is no," Dr. Nagele said in a press statement.

The researchers noted that some patients might have taken vitamin B supplements available over the counter, which could have influenced the results. A larger study with more participants could help study the effects of nitrous oxide on the risk of heart attacks better.

The results of this study were published in July in Anesthesiology, the Journal of the American Society of Anesthesiologists.

The study was funded by the National Institute for General Medical Sciences and the National Institute for Research Resources of the National Institutes of Health (NIH). It also received support from a grant from the Foundation for Anesthesia Education and Research. Roche Diagnostics provided funding for certain tests but according to the authors, the company had no role in the conducting the study.

Review Date: 
June 21, 2013