As marijuana (cannabis) use grows more common, a Duke University School of Medicine medical review warns it can make surgeries and procedures riskier.
Published in the journal Current Opinions in Anesthesiology, the review highlights recent research showing cannabis users may require higher doses of propofol, a common anesthesia drug, to be properly sedated and pain-free during surgery. In some cases, doses were 15% to 30% higher than those needed in non-users.
“Cannabis use is a relevant factor in anesthesia planning,” said lead author Ruba Sajdeya, MD, PhD, a medical instructor in the Duke Department of Anesthesiology. “We’re urging clinicians to ask about it routinely and plan accordingly.”
Propofol is widely used to induce unconsciousness — effectively putting patients to sleep — before surgery due to its rapid effect, but it can also impact heart function. Adjusting doses increases the risk of complications, including under-sedation and cardiovascular side effects.
The review calls for more research to establish best practices, and routine pre-operative screening for cannabis use, a step that’s still not standard at many hospitals, echoing similar recommendations.
Authors note that while cannabis is legal in some form in nearly 40 U.S. states and used by roughly 1 in 5 Americans, many patients keep quiet about it. Some may hesitate due to lingering stigma, while others may not consider it a “drug” worth mentioning before surgery.
It leaves anesthesiologists navigating increasingly complex patient cases, often without clear guidance.
Cannabis users are a particular challenge. There is no consensus on how much cannabis use – daily, weekly, or occasional – may alter propofol’s effectiveness. Nor are there guidelines for tapering cannabis use before surgery.
Compounds in cannabis, including tetrahydrocannabinol (THC) and cannabidiol (CBD), may change how the body responds to anesthesia — though scientists are still trying to figure out exactly how. So far, studies have not confirmed a direct cause-and-effect, but they do show a consistent association. The effect may stem from pharmacological resistance or simply individual differences in how patients respond to anesthetic drugs.
“Ultimately we need better, high-quality research to develop evidence-based practices,” Sajdeya said.
But research on cannabis is tough because of federal restrictions, making it hard to gather solid evidence.
Until more data is available, authors advocate for a cautious, individualized approach with patients. Clinicians should be prepared to adjust sedative doses when necessary and to monitor patients closely for cardiovascular instability, such as changes in blood pressure.
“This is about ensuring safety,” said Sajdeya who, in 2023, created a natural language processing algorithm to detect if cannabis use is included in doctors’ notes in electronic medical records. “As cannabis use becomes more prevalent, our understanding of how it interacts with anesthetic drugs used every day in operating rooms must keep pace.”
Additional Authors: Miriam Treggiari, MD, PhD, MPH, at Duke and Samer Narouze, MD, PhD, at Western University in Ohio.
Funding: National Institutes of Health T32 Integrated Training in Anesthesiology Program at Duke University.