Do Cannabis Users Need More Anesthesia During Surgery?

TOPLINE: 

Cannabis users aged 65 years or older undergoing general anesthesia for surgery required higher doses of inhalational anesthetics than nonusers. However, the clinical relevance of this difference remains unclear.

METHODOLOGY:

• To assess if cannabis use leads to higher doses of inhalational anesthesia during surgery, the researchers conducted a retrospective cohort study comparing the average intraoperative minimum alveolar concentrations of volatile anesthetics (isoflurane and sevoflurane) between older adults who used cannabis products and those who did not.
• The researchers reviewed electronic health records of 22,476 patients aged 65 years or older who underwent surgery at the University of Florida Health System between 2018 and 2020.
• Overall, 268 patients who reported using cannabis within 60 days of surgery (median age, 69 years; 35% women) were matched to 1072 nonusers.
• The median duration of anesthesia was 175 minutes.
• The primary outcome was the intraoperative time-weighted average of isoflurane or sevoflurane minimum alveolar concentration equivalents.

TAKEAWAY:

• Cannabis users had significantly higher average minimum alveolar concentrations of isoflurane or sevoflurane than nonusers (mean, 0.58 vs 0.54; mean difference, 0.04; P = .021).
• The findings were confirmed in a sensitivity analysis that revealed higher mean average minimum alveolar concentrations of anesthesia in cannabis users than in nonusers (0.57 vs 0.53; P = .029).
• Although the 0.04 difference in minimum alveolar concentration between cannabis users and nonusers was statistically significant, its clinical importance is unclear.

IN PRACTICE:

“While recent guidelines underscore the importance of universal screening for cannabinoids before surgery, caution is paramount to prevent clinical bias leading to the administration of unnecessary higher doses of inhalational anesthesia, especially as robust evidence supporting such practices remains lacking,” the authors of the study wrote.

SOURCE:

This study was led by Ruba Sajdeya, MD, PhD, of the Department of Epidemiology at the University of Florida, Gainesville, Florida, and was published online on July 9, 2024, in Anesthesiology.

LIMITATIONS: 

This study lacked access to prescription or dispensed medications, including opioids, which may have introduced residual confounding. Potential underdocumentation of cannabis use in medical records could have led to exposure misclassification. The causality between cannabis usage and increased anesthetic dosing could not be established due to the observational nature of this study. 

DISCLOSURES:

This study was supported by the National Institute on Aging, the National Institutes of Health, and in part by the University of Florida Clinical and Translational Science Institute. Some authors declared receiving research support, consulting fees, and honoraria and having other ties with pharmaceutical companies and various other sources. 

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.