Before undergoing surgery, patients should tell their anesthesiologist if they're a heavy cannabis user and, according to new guidelines, anesthesiologists should be asking about use.

Cannabis use, particularly when it's regular and heavy, can leave patients in more pain than normal after surgery, and getting high just before an operation can put a patient at risk for heart problems, even a heart attack, said Dr. Samer Narouze, president of the American Society of Regional Anesthesia and Pain Medicine. The society released the guidelines Jan. 3, and they are intended to be both educational and instructive, Narouze said. While medical schools are now starting to teach about cannabis, most practicing doctors learned little about the drug or the body's reaction to it during their training. "It's a problem for every practicing anesthesiologist. They have this patient and they just don't know what to do," said Narouze, also chairman of the Center for Pain Medicine at Western Reserve Hospital in Cuyahoga Falls, Ohio.

The guidelines recommend anesthesiologists ask patients whether they use cannabis, how much, how often, how recently, what type of marijuana and whether it was smoked or ingested. The guidelines also call for postponing elective surgery if a patient arrives high and educating pregnant patients about the risks of using marijuana on their baby.