Research Shows Cannabis Users Experience More Pain After Surgery

New research shows that cannabis users experience more pain and require more painkillers after surgery.

People who use cannabis may experience more pain after surgery than nonusers, according to research presented recently at the Anesthesiology 2022 conference in New Orleans. In a study of nearly 35,000 patients, those who used cannabis experienced 14% more pain in the first 24 hours following a surgical procedure.

“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,” said Elyad Ekrami, M.D., lead author of the study and clinical research fellow of the Outcomes Research Department at the 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.”

To complete the study, researchers reviewed the medical records of 34,521 adult patients who had elective surgeries at the Cleveland Clinic from January 2010 to December 2020. Among the study group, 1,681 patients were identified as cannabis users. The cannabis users had all used cannabis within the 30 days prior to surgery, while the nonusers reported that they had never used marijuana.

The researchers’ analysis showed that the cannabis users experienced 14% more pain during the first 24 hours following surgery than the patients who did not use marijuana. Cannabis users also consumed 7% more opioid painkillers than other patients, a figure that the researchers noted was not significant although could be clinically relevant. 

Ekrami noted that previous studies exploring the link between cannabis use and painkillers have produced varying results. But he added that the new research, which was presented at the annual meeting of the American Society of Anesthesiologists, varied with other studies in several key ways.

“The association between cannabis use, pain scores and opioid consumption has been reported before in smaller studies, but they’ve had conflicting results,” said Ekrami. “Our study has a much larger sample size and does not include patients with chronic pain diagnosis or those who received regional anesthesia, which would have seriously conflicted our results. Furthermore, our study groups were balanced by confounding factors including age, sex, tobacco and other illicit drug use, as well as depression and psychological disorders.”

Other Studies Showed Similar Results

The new study is consistent with the results of a small 2020 study that found that, compared to nonusers, cannabis users who underwent surgery to repair a fractured tibia required more anesthetic during the procedure, had higher pain scores after surgery and needed more opioids while recovering in the hospital.

“There is some evidence that cannabis may be beneficial for chronic and nerve pain. However, early research suggests that this is not the case for acute pain such as for surgery of a broken leg,” said Ian Holmen, M.D., lead author of the study and an anesthesiology resident at the University of Colorado Hospital, Aurora. “We now understand patients who chronically use opioids prior to surgery often have exaggerated pain responses and need increased pain medication after surgery because they have an increased tolerance. We speculate that cannabis use may cause a similar effect, but we need more research to determine if this is the case.”

In light of the research linking cannabis use with differences in the effectiveness of anesthesia and painkillers, David Hepner, M.D. suggested that patients who use cannabis and are scheduled for surgery come clean about their use of the plant with their anesthesiologist.

“Regular users of marijuana generally need larger doses of anesthesia medicines in order to achieve the same degree of sedation,” Hepner wrote in the Harvard Health Blog in 2020. “If you don’t tell your anesthesiologist how much marijuana you smoke, he or she may underestimate how much anesthesia will be needed for you to ‘go to sleep’ and stay asleep during your procedure.”

Ekrami noted that additional research is needed to further explore how cannabis use might affect surgical outcomes. 

“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 post-surgical pain control,” he said.

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