Cannabis, Pain, and Complications: A Prospective Analysis of Cannabis Use, Opiate Consumption, and Postoperative Outcomes following Cancer-Related Abdominal Surgery.

Background: Cannabis use is increasing and is of particular interest to patients with cancer. There is no prospective data regarding its impact on perioperative outcomes. We asked how chronic usage of cannabis compounds (cannabinoids) impacted postoperative pain, opiate use, and complications after abdominal surgery for the treatment of cancer. Patients And Methods: This was a single center prospective observational cohort study conducted from 9/2021-3/2024 of patients 21+ years old, undergoing abdominal surgery for the treatment of cancer, and either chronic cannabinoid users (>/=1x/week for last 3 months) or non-users (for the last year). Plasma cannabinoids were measured preoperatively on the day of surgery. Results: Of 223 patients screened, 64 subjects completed enrollment (24 chronic cannabinoid users, 40 non-users). Most were male (67%) and underwent an open abdominal surgery (75%). 41% developed complications, 23% of which were severe (grade 3+) complications. Chronic users with detectable cannabinoid levels had significantly higher pain scores, which persisted in multivariable analysis. Chronic users also received significantly more morphine milligram equivalents (MME) (8-hours postoperatively: 28.8 vs 9.8, p=0.036, during the total hospitalization: 273 vs 202.1, p=0.046, prescribed: 150 vs 100, p=0.047, taken through POD30: 67.5 vs 5, p=0.03). Differences in MME prescribed and taken postoperatively persisted in multivariable analysis. Chronic users had fewer overall complications (5/23 (22%) vs 21/41 (51%), p=0.025), but similar frequency to non-users for severe complications (2/23 (8.7%) vs 4/41 (9.8%), p=0.33). Conclusions: Chronic cannabinoid use increased postoperative pain and MME use for patients undergoing abdominal surgery for the treatment of cancer, but did not increase complications. Further study regarding preoperative cannabinoid cessation and use of cannabinoids for postoperative pain is warranted.