Effect of patient marijuana use on perioperative opioid requirements.

The effect of chronic marijuana use on patients is unknown, including in the surgical setting. Marijuana produces many effects on the body, which should be considered when providing medical care. Chronic marijuana use may affect surgical opioid requirements. To explore this possibility, an observational study was completed by conducting a retrospective chart review of patients who underwent surgery with general anesthesia. Patients were identified in the electronic medical record via self-reporting as marijuana users (users) or nonmarijuana users (nonusers). Users and nonusers were case-matched based on age, gender, weight, and procedure. After case matching, 570 patients' charts were analyzed, and intraoperative opioid, intraoperative propofol, and post-anesthesia care unit opioid requirements were compared. Marijuana users required less intraoperative opioids (mean [standard deviation (SD)] 27.2 [20.5] morphine milligram equivalents [MMEs]) compared to those who were marijuana nonusers (31.3 [22.1] MME). These results show a statistically significant difference in the intraoperative opioid requirement between case-matched users and nonusers (p = 0.02), with p = 0.013 after statistical adjustment for racial differences between the marijuana user and nonuser cohorts. Users and nonusers required similar amounts of intraoperative propofol (242.2 [220.2] and 257.8 [250.9], respectively) and post-operative opioids (7.3 [6.0] and 8.0 [9.0], respectively). The differences in intraoperative propofol and post-operative opioid requirements were not different statistically with p-values of 0.43 and 0.31, respectively. Based on this study population, marijuana users required less intraoperative opioids when compared to case-matched marijuana nonusers, with no difference in intraoperative propofol or post-operative opioid requirements. Perspective: Typical preoperative screening includes queries about patient substance use including marijuana, but details such as frequency and length of use are infrequently asked. The addition of these details to the assessment may provide improved understanding of a patient's surgical opioid requirements.