Undisclosed Cannabis Use May Increase Risk of Waking During Surgery, Doctors Warn

Patients who do not disclose regular cannabis use or smoking to their surgical teams may face a heightened risk of reduced sedative effectiveness and, in rare cases, waking during procedures, anesthesiologists warn.

Dr. Kunal Sood, an anesthesiologist and pain specialist in Maryland, said clinicians have observed that "[Regular] marijuana use may... change how the body processes drugs... and cause anesthetics to break down more quickly. That's why it's important to be honest with your anesthesia team about your medical and social history, including cannabis use." He and other specialists say that failing to report such habits can complicate dosing and monitoring during anesthesia.

Specialists explain two main mechanisms by which cannabis can influence anesthesia. First, regular cannabis use can induce certain liver enzymes that metabolize drugs, accelerating the breakdown of sedatives and some painkillers and reducing their duration of action. Second, tetrahydrocannabinol (THC) and other cannabinoids act on brain systems that overlap with the targets of anesthetic drugs, which can blunt the drugs' sedative effects. As a result, standard doses of anesthetics or analgesics may be less effective in frequent cannabis users.

The prevalence of cannabis use in the United States underscores the clinical relevance of the issue. An estimated three in 20 Americans — about 51 million people — use cannabis at least once a week for recreational or medical purposes, and nearly 18 million use it daily or near daily. With those numbers, anesthesiologists say routine preoperative screening that includes questions about marijuana and tobacco use is important for individualizing care.

Anesthesiology teams can adjust plans when they have accurate information. That may include altering drug selection, adjusting dosing, and using enhanced monitoring to reduce the risk of awareness during surgery, clinicians say. Preoperative conversations also allow clinicians to counsel patients on temporary cessation strategies and other risk-reduction measures when appropriate.

Awareness during surgery, sometimes called intraoperative awareness, is an uncommon but distressing complication in which a patient becomes conscious during a procedure while receiving general anesthesia. Experts emphasize that it remains rare, but they say the combination of altered drug metabolism and overlapping central nervous system effects means regular cannabis users could require different intraoperative management to maintain adequate sedation.

Physicians and professional societies advise patients to give a full medical and social history before procedures, including the frequency and recency of cannabis or tobacco use. Clinicians say honesty helps them tailor anesthesia safely and reduces the chance of complications linked to under-sedation.

Patients with questions about how their cannabis or smoking habits might affect planned procedures should raise them during preoperative assessments. Anesthesiologists can then explain how those habits may influence medication choices and monitoring, and recommend steps to minimize risks. Accurate disclosure is central to safe perioperative care, clinicians say.