Cannabis users experience worse postoperative pain

Pain control after a surgery may be tougher for cannabis users than for nonusers, with cannabis use being linked to higher postoperative pain scores and a trend toward greater use of opioids, as reported in a large study presented at the Anesthesiology 2022 Annual Meeting.

Of note, cannabis users consumed a mean of 67 mg in IV morphine equivalents of opioids during the first 24 hours after an elective surgery. This was 8-mg greater than the amount of opioids consumed by cannabis nonusers. [Anesthesiology 2022, abstract A2061]

Moreover, the median time-weighted average (TWA) of pain scores during the first 24 postoperative hours were higher by 1.4 points among cannabis users (5.5 vs 4.1).

“Cannabis is the most commonly used illicit drug in the United States and increasingly used as an alternative treatment for chronic pain, but there is limited data that shows how it affects patient outcomes after surgery,” according to Dr Elyad Ekrami, lead author of the study and clinical research fellow of the Outcomes Research Department at Cleveland Clinic’s Anesthesiology Institute.

“Our study shows that adults who use cannabis are having more—not less—postoperative pain. Consequently, they have higher opioid consumption after surgery,” Ekrami said.

In their study that spanned more than 10 years, Ekrami and colleagues looked at 34,521 adult patients who had undergone elective surgeries at Cleveland Clinic. All surgical procedures lasted more than an hour and required patients to stay at the hospital for at least 24 hours. None of the patients had regional or epidural analgesia or any perioperative regional blocks and a chronic pain diagnosis.

Of the patients, 1,681 were cannabis users. Cannabis use was defined as exposure to cannabis within 30 days before surgery.

In multivariable analyses adjusted for inverse probability of treatment weighting, cannabis use showed no significant association with opioid consumption during the first 24 postoperative hours, with the ratio of geometric means of opioid consumption in cannabis users vs nonusers being 1.07 (95 percent confidence interval [CI], 0.96–1.19; p=0.19).

However, cannabis use was significantly associated with greater TWA pain score during the first 24 postoperative hours (difference in mean TWA pain score, 0.58, 95 percent CI, 0.48–0.68; p<0.001).

“The association between cannabis use, pain scores, and opioid consumption has been reported before in smaller studies, but they’ve had conflicting results. Our study has a much larger sample size and does not include patients with chronic pain diagnosis or those who received regional anaesthesia, which would have seriously conflicted our results,” Ekrami pointed out.

“Physicians should consider that patients using cannabis may have more pain and require slightly higher doses of opioids after surgery, emphasizing the need to continue exploring a multimodal approach to postsurgical pain control,” he said.  

Ekrami called for more research to further establish cannabis’ effects on surgical outcomes.