Nitrous oxide does not up heart attack risk during surgery

Washington: Nitrous oxide - best known as laughing gas - has been one of the world`s oldest and most widely used anaesthetics.

However, despite its popularity, experts have questioned its impact on the risk of a heart attack during surgery or soon afterward.

But those fears are unfounded, a new study by researchers at Washington University School of Medicine in St. Louis suggests.

"It`s been known for quite a while that laughing gas inactivates vitamin B12 and, by doing so, increases blood levels of the amino acid homocysteine," lead author Peter Nagele, MD, assistant professor of anesthesiology and genetics, said.

"That was thought to raise the risk of a heart attack during and after surgery, but we found no evidence of that in this study," he said.

Nitrous oxide normally is used as an adjunct during general anesthesia because by itself the drug isn`t strong enough to keep patients unconscious during surgical procedures.

The drug`s influence on B vitamins and homocysteine is unrelated to its anesthetic effects.

Nagele and his colleagues followed 500 surgery patients at Barnes-Jewish Hospital in St. Louis who had been diagnosed with coronary artery disease, heart failure or other health problems that could contribute to a heart attack.

All subjects in the study had noncardiac surgery and received nitrous oxide anesthesia.

The patients were divided into two groups. Half received intravenous vitamin B12 and folic acid to help prevent homocysteine levels from rising during surgery. The others did not get the intravenous B vitamins.

"There were no differences between the groups with regard to heart attack risk," Nagele said.

"The B vitamins kept homocysteine levels from rising, but that didn`t influence heart attack risk," he added.

The findings are set to be published in the journal Anesthesiology.