Abstract
Introduction Granisetron is a selective 5-hydroxytryptamine type 3 (5-HT3) receptor antagonist approved in Japan for the prophylaxis of postoperative nausea and vomiting (PONV). According to the Japanese package insert, a fixed intravenous dose of 1 mg is recommended; however, evidence for its effectiveness in patients undergoing laparoscopic colorectal surgery in a clinical context characterized by multiple established PONV risk factors remains limited. We evaluated the association between prophylactic granisetron 1 mg and PONV-related outcomes in this setting. Methods This single-center retrospective observational study included adult patients who underwent elective laparoscopic colorectal surgery between January 2018 and July 2024. All patients received inhalational anesthesia and postoperative analgesia consisting of a peripheral nerve block and continuous intravenous fentanyl infusion. Patients were divided into a granisetron group (G group: 1 mg intravenously at the end of surgery) and a no-granisetron group (N group). The primary outcome was PONV within 24 hours. Secondary outcomes were rescue antiemetic use within 24 hours and complete response (no PONV and no rescue antiemetic use). Multivariable logistic regression was performed with adjustment for prespecified covariates and surgical year. Sensitivity analyses included propensity score overlap weighting and restriction to surgeries performed in 2022 or later. Within the granisetron group, an exploratory multivariable analysis for complete response included sex, age, and granisetron dose per body weight. Results A total of 377 patients were included (G group, n = 101; N group, n = 276). PONV occurred less frequently in the granisetron group than in the no-granisetron group (34/101 (33.7%) vs 129/276 (46.7%), p = 0.026), whereas rescue antiemetic use was similar (33/101 (32.7%) vs 96/276 (34.8%), p = 0.806). Complete response tended to be higher in the granisetron group (65/101 (64.4%) vs 146/276 (52.9%), p = 0.061). After adjustment, granisetron was associated with lower odds of PONV (adjusted odds ratio (aOR) 0.355, 95% CI 0.181-0.697; p = 0.003) and higher odds of complete response (aOR 2.826, 95% CI 1.444-5.531; p = 0.002). The association with rescue antiemetic use did not reach statistical significance. Sensitivity analyses using propensity score overlap weighting and restriction to surgeries performed in 2022 or later yielded directionally consistent results, although estimates were less precise. Conclusions In patients undergoing laparoscopic colorectal surgery in a setting with multiple established risk factors for PONV, prophylactic administration of a fixed 1 mg dose of granisetron may be associated with improved PONV outcomes within 24 hours.