• Posted July 11, 2023

Strong Marijuana Habit Could Raise Odds for Complications During Surgery

Using marijuana regularly might increase the risk for complications during and after surgery, and doctors should address this when planning operations, a new study suggests.

People with a cannabis use disorder are 20% more likely to have serious complications, such as stroke or blood clots, after a major operation than patients who aren't dependent on marijuana, researchers say.

"It turned out to be not a huge effect but significant enough to where patients need to pay attention to their cannabis use," said lead researcher Dr. Paul Potnuru. He is an assistant professor in the department of anesthesiology, critical care and pain medicine at the University of Texas McGovern Medical School, in Houston.

Doctors need to know how much cannabis patients are using "and how often, and if it's heavy use or overuse, that can have negative impacts," Potnuru said.

The study defines cannabis use disorder as continued excessive use of marijuana even when it's causing health and social problems or interfering with work. In 2021, over 16 million Americans had a cannabis use disorder, according to the U.S. National Institute on Drug Abuse.

This study can't prove that marijuana is responsible for complications after surgery, only that there appears to be an association, Potnuru said.

The association may have a biological base, he noted. The psychoactive substance in cannabis, THC, can cause blood vessels to spasm, which can lead to heart attacks or strokes. THC can also suppress the immune system, Potnuru added.

Whether patients should stop using marijuana before major elective surgery to avoid complications isn't known, he said.

"This is guessing, but it's probably going to turn out to be like smoking tobacco where it's better if you stop using it heavily, especially before surgery," Potnuru said. "It seems to have enough of an impact to where we need to pay attention to it."

In January, the American Society of Regional Anesthesia (ASRA) and Pain Medicine released guidelines for screening all patients for cannabis use before surgery. Patients should be informed of the increased risk of adverse outcomes, the society says.

“Before surgery, anesthesiologists should ask patients if they use cannabis — whether medicinally or recreationally — and be prepared to possibly change the anesthesia plan or delay the procedure in certain situations,” said Dr. Samer Narouze, senior author and ASRA Pain Medicine president at the time.

For the new study, Potnuru's team used the U.S. National Inpatient Sample database to analyze more than 62,000 hospitalizations for major elective surgeries performed from 2016 to 2019. They zeroed in on 6,211 patients with cannabis use disorder and 6,211 without it.

The investigators found that patients with cannabis use disorder had higher risks of heart attack, stroke, kidney problems, respiratory failure, blood clots, hospital-acquired infections and additional surgical procedures related to complications. The rate of complications was about 8% for this group versus roughly 7% for patients without cannabis use disorder.

As a result, their hospital stays cost more, the findings showed. These extra costs were due to treatments and medication used to deal with surgical complications, Potnuru noted.

Not everyone agrees with Potnuru's conclusions, however.

One expert sees multiple problems with this study, from the definition of cannabis use disorder to its supposed link with surgical complications.

"We need to start from scratch with our definition of 'cannabis addiction' — what they are using doesn't work. Some people get addicted, but the numbers are vastly inflated," said Dr. Peter Grinspoon, a cannabis specialist at Massachusetts General Hospital and Harvard Medical School in Boston.

Also, in many electronic medical record systems, there was no way to designate who is addicted to cannabis and who is a casual user, Grinspoon said. "So many of the diagnoses of cannabis use disorder in the electronic medical record systems are based on nonexistent addictions and diagnoses that were essentially fabricated," he said.

"The best you can say about this study is that it suggests that medical cannabis users might be sicker patients with more diseases and symptoms," Grinspoon explained. "This study doesn't in any way imply that cannabis is causing or contributing to any of the problems or worsened outcomes that they are suggesting it may be contributing to."

Given the lack of proof of its harm, Grinspoon thinks that quizzing patients about their marijuana use places an unnecessary burden on doctors.

"As doctors, we barely have time to cover the basics, and to suggest that we do something irrelevant and unsupported, such as this, actually harms the patient as we are taking time away from important risk stratification, such as alcohol, tobacco, blood pressure, exercise tolerance, etc. — things you really do have to pay attention to for risk stratification," he said.

"Of course, we need to understand the harms and benefits [of marijuana], but this study, unfortunately, does not contribute much of anything," Grinspoon said.

The report was published online July 5 in JAMA Surgery.

More information

For more on marijuana, head to the U.S. National Institute on Drug Abuse.

SOURCES: Paul Potnuru, MD, assistant professor, department of anesthesiology, critical care and pain medicine, McGovern Medical School, University of Texas, Houston; Peter Grinspoon, MD, cannabis specialist, Massachusetts General Hospital and Harvard Medical School, Boston; JAMA Surgery, July 5, 2023, online