Cannabis use linked to higher heart attack risk during and after surgery, but fewer blood clots

by American Society of Anesthesiologists

edited by Sadie Harley, reviewed by Andrew Zinin

Sadie Harley

Scientific Editor

Meet our editorial team
Behind our editorial process

Andrew Zinin

Chief Editor

Meet our editorial team
Behind our editorial process Editors' notes

This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility:

fact-checked

trusted source

proofread

The GIST Add to Preferred Sources

As marijuana use becomes more common and legal in most U.S. states, patients who use cannabis may face a significantly higher risk of heart attack around the time of surgery, while also showing an unexpected lower risk of dangerous blood clots in the veins, suggests a study presented at the ANESTHESIOLOGY 2026 annual meeting.

"Our findings show that it is vitally important to tell your anesthesiologist before your procedure if you use marijuana, whether for medical or recreational purposes," said Nader D. Nader, lead author of the study and professor of anesthesiology and surgery at the Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, New York.

"This is not about judgment; it is about safety. Cannabis can affect your heart, your blood vessels and how your body responds to anesthesia. Knowing about a patient's cannabis use allows the anesthesiologist to take extra precautions to keep patients safe during and after surgery."

Reviewing five studies including data from 44,312 surgical patients, the authors found cannabis use was associated with a 46% increased risk of myocardial infarction, or heart attack, during or shortly after surgery compared to nonusers. They found no significant links between cannabis use and stroke, respiratory failure, acute kidney injury or death.

In a surprising finding, researchers found cannabis use was associated with a 22% lower risk of venous thromboembolism, or blood clots in the veins. The authors said this finding highlights the complex effects of cannabis on the heart and blood vessels and warrants further study.

Researchers cautioned that the lower blood-clot risk does not establish that cannabis has a protective effect. Cannabis acts on receptors in the body that may influence inflammation and clotting in different ways. More information is needed to understand the links between cannabis use, heart attacks and blood clots around the time of surgery, according to the authors.

Tetrahydrocannabinol (THC), the main psychoactive component in cannabis, can increase heart rate, blood pressure and the heart's need for oxygen, researchers said. It may also trigger spasms in the arteries that supply blood to the heart. Together, these effects can increase the risk of a heart attack, particularly during the physiological stress of anesthesia and surgery.

Patients should not assume marijuana is harmless because it is legal or plant-derived, the study authors note. Cannabis use can pose significant risks during anesthesia and surgery, potentially compromising patient safety.

Patients who use cannabis should tell their anesthesiologist and surgical team how often they use it, what form they use and when they last used it. That information will affect decisions about cardiovascular monitoring, the anesthetic plan, blood-thinning medications or whether an elective procedure should be delayed.

"Today's cannabis products are far more potent than they were decades ago, and higher THC levels can have serious cardiovascular effects," said study co-author Rose Berkun, associate professor of anesthesiology, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, New York.

"Educating patients about these risks and encouraging them to disclose cannabis use to both their surgeon and anesthesiologist before surgery are important steps in helping to provide the safest possible care."

Key medical concepts

Myocardial infarctionVenous Thromboembolism

Clinical categories

AnesthesiologyCardiologyCommon illnesses & Prevention Provided by American Society of Anesthesiologists Who's behind this story?

Sadie Harley

BSc Life Sciences & Ecology. Microbiology lab background with pharmaceutical news experience in oil, gas, and renewable industries. Full profile →

Andrew Zinin

Master's in physics with research experience. Long-time science news enthusiast. Plays key role in Science X's editorial success. Full profile →

Citation: Cannabis use linked to higher heart attack risk during and after surgery, but fewer blood clots (2026, October 18) retrieved 19 October 2026 from https://medicalxpress.com/news/2026-10-cannabis-linked-higher-heart-surgery.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.