Study suggests cannabis consumers need more anesthesia, pain meds

Research on the effects of cannabis consumption on people needing anesthesia for medical procedures is growing. And new, first-of-its kind research presented Monday at the Anesthesiology 2020 annual meeting has shed new light on why medical professionals should know about a patient’s cannabis consumption. 

An excerpt of this small retrospective review study has been published in the peer-reviewed Journal of Clinical Anesthesia; the authors expect that a full version under review will be published in the peer-reviewed Canadian Journal of Anesthesia. 

For this study, researchers compared cannabis consumers and non-consumers before and after surgery for a broken tibia, or shin bone. In total, 118 patients seeking treatment at the University of Colorado Hospital participated in the study. One-quarter (25.4%) reported that they consumed cannabis before the surgery, though researchers did not have data related to frequency, time or date of consumption, or whether the cannabis was smoked, vaped, or eaten.

Researchers compared the amount of anesthesia needed by both groups, those who consumed cannabis and those who didn’t, and also their pain scores and how much opioid-based medication was needed. 

The group who consumed cannabis needed more sevoflurane, an anesthesia. For example, this group needed 37.4 ml vs. 25 ml. This group also reported more pain, with their pain scores roughly a 6, versis 4.8, which researchers note is a “statistically significant difference.” This group also received 58% more opioid-based painkillers, or roughly an average of 155.9 morphine milligram equivalents daily vs. 98.6 milligrams for the non-consumer group. 

The findings related to the need for more anesthesia surprised researchers most, lead author Ian Holmen, who is also anesthesiology resident at the University of Colorado Hospital, Aurora, told Cannabis Wire

“We did not actually anticipate that. The main literature has suggested that there is an increased dose of Propofol required,” Holmen said, referencing a common anesthetic. “But, no one had previously reported across a broader group of patients an increased necessity for sevoflurane,” he added, referencing another drug used during anesthesia. 

The main takeaway, Holmen said, is that medical providers need to be aware that there is a possibility for increased doses of sevoflurane for some patients undergoing operations. Part of the reason for that, Holmen added, is that the drug can cause low blood pressure in some patients. 

“For a healthy young patient, that might not be a problem at all. But for a patient who maybe has lung problems or other heart problems, comorbidities going into that case, slight adjustments or changes in blood pressure can actually be fairly consequential, depending on how severe it is,” Holmen said. 

When asked whether there’s been a coordinated effort to encourage medical professionals and patients to communicate about cannabis use, Holmen said that, at least based on his time in medical school, he couldn’t recall any such “big movement.” And while doctors often ask patients about alcohol and “illicit” drug use during the collection of medical history, oftentimes a doctor won’t specifically isolate cannabis. Holmen said that in his personal practice in Colorado, where voters legalized in 2012, he’s moved to specifically asking patients about cannabis use.

“I think an initiative like that to be more deliberate about asking specifically about cannabis would be worthwhile, especially given the number of patients who are now presenting to the [operating room] with having had recreational cannabis use prior,” he said. 

While other literature on cannabis consumption and pain, or anesthesia required, have been published, the other main takeaway, Holmen said, is that more research is needed, especially given the pace of legalization. 

Holmen said he plans to continue research at the intersection of anesthesia and cannabis consumption. 

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