June 19, 2013
Laughing Gas Does Not Lead To Heart Attacks, According To New Study
Lee Rannals for redOrbit.com - Your Universe Online
Researchers at Washington University School of Medicine in St. Louis determined that laughing gas does not increase the risk of a heart attack during surgery.
Nitrous oxide, more commonly known as laughing gas, is one of the world's oldest and most widely used anesthetics. However, some experts have questioned whether the anesthetic raises the risk of a heart attack during surgery or soon afterward.
“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,” said lead author Peter Nagele, assistant professor of anesthesiology and genetics at Washington University School of Medicine. “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.”
The researchers followed 500 surgery patients who were diagnosed with coronary artery disease, heart failure or other chronic health problems known to contribute to heart attack. All of the patients in the study had noncardiac surgery and received nitrous oxide anesthesia. The participants were divided into two groups, half of which received intravenous vitamin B12 and folic acid to prevent homocysteine levels from rising during surgery. The other half of the patients did not receive intravenous vitamin treatments.
“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.”
Researchers monitored a key marker of heart damage known as cardiac troponin I for 72 hours in order to detect heart attacks during and after surgery. They found no link between patients' homocysteine and troponin levels.
The team, who reported their findings in the journal Anesthesiology, also looked at gene variations that naturally lead to elevated homocysteine. Individuals with common variants in the MTHFR gene make excess homocysteine, and if people with those variants get nitrous oxide anesthesia their levels can climb higher.
Only 3.1 percent of patients with the high-risk genetic variants had heart attacks during or after surgery, compared with 4.7 percent of the patients who did not have the risky variants. Neither the gene variations nor treatment with B vitamins appeared to have an effect on troponin levels following surgery.
“People who had the gene variant did, indeed, develop very high levels of homocysteine in response to nitrous oxide,” Nagele said. "So the question is whether those patients would be at a higher risk for heart attack, and that answer is no.”
Although this study indicates that laughing gas is not harmful to the heart, it can be detrimental to the planet. A study found that nitrous oxide accounts for nine percent of all greenhouse gases, and is 300 times more potent than carbon dioxide once in the atmosphere. Agriculture accounts for about 70 percent of nitrous oxide emissions.