Cannabis Use Can Affect Anesthesia: Why Patients Should Tell Their Care Team
Patients who use cannabis should tell their surgeon and anesthesia team before a procedure, regardless of whether they use marijuana for medical or recreational purposes. Cannabis use does not automatically mean surgery must be canceled, but it can affect sedation needs, heart rate, blood pressure, breathing and postoperative pain management.
The evidence is not absolute, and cannabis users do not all require the same anesthetic dose. However, several studies have found that regular users may need more medication to achieve adequate sedation. In a 2021 case-control study of patients undergoing endoscopy, people who reported cannabis use received more propofol than nonusers, with daily users requiring more than weekly or occasional users. Because the study was observational and conducted at a single outpatient clinic, it shows an association rather than proving that cannabis directly causes higher anesthetic requirements.
Other research has produced mixed results, and the amount of anesthesia used depends on many factors, including a patient’s age, weight, health, medications, type and length of procedure, and whether the person is acutely intoxicated. The 2023 consensus guidelines from ASRA Pain Medicine note that limited evidence suggests regular, long-term users who are not intoxicated may require more anesthetic, while acute intoxication can affect anesthetic needs in a different direction.
That is why the anesthesia team needs specific information—not merely a yes-or-no answer about marijuana. Patients should be prepared to discuss:
- how often they use cannabis;
- the amount and strength of the product;
- whether they smoke, vape, eat or otherwise ingest it;
- when they last used it; and
- whether they also use alcohol, opioids, sedatives or other drugs.
As anesthesiologist David Hepner, MD, MPH, explained in a Harvard Health article, the route, frequency and amount of cannabis use can influence how a patient responds to anesthesia. The information helps clinicians choose medications, adjust doses while monitoring the patient and anticipate possible complications.
Cannabis can also have cardiovascular and respiratory effects that matter around surgery. Smoking may irritate the airways, while cannabis can alter heart rate and blood pressure. The American Society of Anesthesiologists advises patients to disclose cannabis use before surgery. ASRA Pain Medicine recommends delaying elective surgery for at least two hours after cannabis smoking in patients who are not acutely intoxicated; the appropriate interval may be longer depending on the patient, product, timing and planned procedure.
Patients should not decide on their own how long to stop using cannabis or change a prescribed treatment without speaking with their healthcare team. The safest approach is to report use honestly during the preoperative assessment and again on the day of the procedure, including use that occurred more recently than expected.
The key message is not that every cannabis consumer will need a larger dose of anesthesia or face serious complications. Rather, cannabis is clinically relevant information that can help the anesthesia team plan safely. Open communication gives clinicians a more complete picture of the patient’s health and allows them to tailor care before, during and after the procedure.
