Study of Effect of Cannabis on Anesthetics Creates Buzz

Anesthesiology News

A small study has concluded that regular cannabis users may require as much as twice the level of sedation before a medical procedure, compared with those who abstain. The report, in the Journal of the American Osteopathic Association ([Epub Apr 15, 2019]. doi:10.7556/jaoa.2019.052), defined regular users as those who smoked or ingested edibles on a weekly or more frequent basis. Those who were either occasional users or abstainers were considered nonusers.

A total of 250 records were reviewed from one endoscopy center, which was located in Colorado where cannabis is now legal. To reduce variance in sedation technique, records pertaining to only one endoscopist were used. Patients were aged 18 years or older; age, sex, and gender were reviewed to determine differences in relative amounts of sedation required for cannabis users and nonusers. Use of alcohol, benzodiazepines and opiates also were reviewed.

Of the trial population (N=250), 25 patients constituted the cannabis group. The cannabis users had undergone 19 colonoscopies, 2 esophagogastroduodenoscopies (EGDs) and 4 colonoscopies/EGDs. The nonuser group had undergone 180 colonoscopies, 27 EGDs and 18 colonoscopies/EGDs. A statistically significant difference was found in the dose of sedative medications needed for endoscopic procedures (Table).

Table. Cannabis Usage and Sedation Required

Sedative	Cannabis Nonusers (n=225)	Cannabis Users (n=25)	Dose Increase in Users, %
Fentanyl, mcg	109.91	125.93	14
Midazolam, mg	7.61	9.15	19.6
Propofol, mg	13.83	44.81	220.5

Several aspects of the study are problematic, which were acknowledged by the authors. Most importantly, the small sample size of users means that definitive conclusions from a report that spotlights a hitherto unreported effect of cannabis use would be premature. The mechanism of the interaction is unknown, and the authors did not speculate on what that might be.

The authors listed several other limitations to the study, including its retrospective design. Certainly, a much larger study is in order, but the hypothesis-generating findings of this study are noteworthy. The researchers concluded, “Knowledge of a patient’s use of cannabis prior to sedation can help prepare endoscopists, nurses, and anesthesia providers for the potential need for more medication, increased costs, and possible risks associated with dose-dependent adverse events.”