Cannabis users need more anesthesia during surgery, more opioids after

While there is significant evidence cannabis can be used to treat chronic pain, a new study suggests it might not be useful for other types of pain and may, in fact, cause harm.

Unpublished research presented at the Anesthesiology 2020 annual meeting shows prior cannabis use may interfere with anesthesia during surgery and is associated with increased pain and higher use of opioids after surgery.

Close to 120 patients who underwent surgery at the University of Colorado Hospital for leg fractures were compared based on whether or not they used cannabis before their surgery.

The authors compared cannabis users to non-users for the amount of anesthesia the patients received during surgery, patient-reported pain scores, and dosage of opioids used during recovery.

The one-quarter of patients who reported using cannabis prior to surgery needed more anesthesia, said their pain was worse during recovery, and used 58 percent more opioids per day they were in the hospital than non-users.

“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,” said Dr. Ian Holmen, lead author of the study and an anesthesiology resident. “We speculate that cannabis use may cause a similar effect, but we need more research to determine if this is the case.”

While anesthetics are generally safe, increased need for anesthesia can pose risks for the elderly and patients with chronic diseases, such as diabetes.

A limitation of this study is that the amount of cannabis used, the frequency of use, and the cannabinoid content of the cultivars used were not reported. As a result, conclusions about the relative effects of using either THC or CBD—or both—prior to surgery could not be made.

“This study shows that it is important for patients to tell their physician anesthesiologist if they have used cannabis products prior to surgery to ensure they receive the best anesthesia and pain control possible, including the use of non-opioid alternatives,” said Dr. Holmen. “It also confirms that more research is needed to understand how cannabis impacts pain.”

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