Study Indicates Cannabis Users Require More Anesthesia for Surgery

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CHICAGO – Data from a study conducted at the University of Colorado Hospital shows cannabis users may require increased levels of anesthesia for surgery, as well as more painkillers during recovery from surgery.

“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,” Dr. Holman added.

The study data was presented at the ANESTHESIOLOGY® 2020 annual meeting, which was held October 2–5, in an online format.

Researchers studied 114 patients with a broken tibia (shin bone). They found thirty of the patients were cannabis users, or about 25 percent of the group. Subjects were not asked about timing or frequency of use, or what type of cannabis they used. The researchers then measured the amount of anesthesia required for each subject, pain scores reported by patients during the procedures, and the amount of pain medication taken by each patient, post surgery.

Research indicated:

  • Cannabis users required increased amounts of anesthesia (Sevoflurane, specifically); an average of 37.4ml to 25ml, for patients that did not use cannabis.
  • Patients who used cannabis reported increased levels of post-operative pain; at an average of six on a scale of ten, compared to 4.8 for non-users.
  • Cannabis users required 58 percent more opioid painkillers (morphine), while recovering in the hospital. The average stay was 2–3 days.