Post-Op Pain Control More Challenging for Cannabis Users

NEW ORLEANS -- Cannabis users reported somewhat worse postoperative pain compared with people who did not use cannabis before surgery, according to a large observational study.

The difference was modest, however, as cannabis users had time-weighted average pain scores after surgery that were 0.58 higher on a scale from 0 to 10 (P<0.001), and they did not have a significantly greater need for higher opioid doses in the first 24 hours after surgery compared with controls, reported Elyad Ekrami, MD, of the Cleveland Clinic, in a poster presentation at the American Society of Anesthesiologists (ASA) annual meeting.

"Physicians should be aware of risk of higher pain scores in patients who use cannabis," the investigators concluded based on their study that spanned more than a decade at the Cleveland Clinic.

The issue has clinical relevance as increasingly more people are using cannabis because of societal acceptance and wider legalization, Ekrami told MedPage Today.

In the U.S., 37 states plus the District of Columbia have laws for medical marijuana use. Patients commonly use cannabis to ease chronic pain, insomnia, and other conditions.

As for postoperative pain, the reported bump in pain score among cannabis users at Cleveland Clinic is in line with the existing -- albeit limited -- literature that supports that cannabis use and cannabinoid use have some adverse effects on postoperative pain control, according to Camille Stewart, MD, of the University of Colorado Anschutz, who was not involved in the current study.

One small study previously found an association between preoperative cannabis use and increased intraoperative sevoflurane. Another report associated cannabinoid use with higher pain scores and a poorer quality of sleep in the early postoperative period in patients undergoing major orthopedic surgery. Finally, there is some evidence that marijuana users admitted to trauma centers with traumatic injuries require greater use of opioid analgesia.

Stewart said her group is currently enrolling patients in a prospective study on postoperative pain control after major abdominal surgery for the treatment of cancer, specifically focusing on differences between daily cannabis users versus nonusers.

As there are also few studies on the effects of cannabis on perioperative safety, that study will also assess differences in postoperative complications, Stewart said in an interview.

Ekrami and colleagues performed a large retrospective analysis of adults who underwent elective surgery lasting more than an hour, and stayed at the hospital at least 24 hours after the surgery. They included over 34,000 patients from the years 2010-2020 and excluded people with chronic pain diagnosis or those who received regional anesthesia (e.g., nerve blocks).

Cannabis exposure was defined as reported use of cannabis within 30 days before surgery.

Compared with the vast majority of nonuser controls, the 1,683 cannabis users tended to be younger and less likely female. They were also more likely to be current and former smokers, have a history of substance abuse, and have a history of depression or anxiety.

Patient characteristics were more balanced after inverse probability of treatment weighting, Ekrami said.

Nevertheless, he acknowledged the potential for unmeasured confounding in the observational analysis.

Stewart also cautioned against relying on self-reported cannabis use data without important variables such as type, frequency, and last use.

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