The Effect of Preoperative Cannabis Use on Postoperative Pain Following Gynaecologic Oncology Surgery

To determine whether cannabis users have different pain scores after gynaecologic oncology surgery than non-cannabis users.

A retrospective chart review was completed for 654 patients who underwent gynaecologic oncology surgery during a 2-year period. The primary outcome was postoperative pain at 12 and 36 hours after surgery using an 11-point pain scale. Secondary outcomes included opioid consumption, length of hospital stay, opioid side effects, and sleep disturbance.

Of all patients included in this study, 64 used cannabis and 590 did not. Propensity score matching and list-wise deletion identified 57 matched pairs. Pain scores were significantly higher at 12 hours (P < 0.001) and 36 hours (P =0.002) after surgery in cannabis users (median pain scores 6 [IQR 5-7]) and 5 [IQR 4-7], respectively) than non-users (median pain scores 4 [IQR 3-6] and 4 ([IQR 2-5], respectively). Median opioid consumption was significantly higher at 12 hours (P = 0.039) and 36 hours (P = 0.044) after surgery in cannabis users (oral morphine equivalent [OME] 20 [IQR 10-40] mg and OME 40 [IQR 10-100] mg, respectively) than non-users (OME 10 [IQR 5-20] mg and OME 30 mg [IQR 7.5-50] mg, respectively]. Sleep disturbance was significantly higher in cannabis users (odds ratio 3.31; P = 0.009).

After gynaecologic oncology surgery, patients who used cannabis preoperatively had higher postoperative pain scores, higher opioid use, and more sleep disturbance than non-users. This suggests that preoperative cannabis use is a risk factor for postoperative pain.