Postoperative Timing of Chemoprophylaxis and Its Impact on Thromboembolism and Bleeding Following Major Abdominal Surgery: A Multicenter Cohort Study

BACKGROUND: Major abdominal surgery is associated with bleeding and venous thromboembolism (VTE) risks. Chemoprophylaxis prevents VTE but increases bleeding risk. When compared with pre- and intra-operative chemoprophylaxis, recent evidence suggests that starting chemoprophylaxis postoperatively lowers the risk of bleeding without compromising VTE protection. This study investigates whether an optimal window exists in the postoperative period for initiating chemoprophylaxis in patients undergoing major abdominal surgery. METHODS: Analysis of pooled data from four multicenter PROTECTinG studies, which investigated the timing of perioperative chemoprophylaxis on bleeding and VTE outcomes following major abdominal surgery. Patients that commenced chemoprophylaxis postoperatively were separated into quartiles based on timing of administration within the first 24 h post-surgery. RESULTS: Overall, 4729 (Abdominal visceral resection N = 668, cholecystectomies N = 573, major ventral hernia repair N = 1701, antireflux surgery N = 1787) consecutive patients had chemoprophylaxis commenced within 24 h following elective surgery. Baseline characteristics were comparable between quartiles. Across quartiles and within each procedural type, the timing of starting chemoprophylaxis was not associated with bleeding (2.6, 1.7, 2.7 and 3.2%, p = 0.130) or clinical VTE (0.8, 0.2, 0.8 and 0.5%, p = 0.131), and did not predict their occurrences on multivariate analysis. CONCLUSION: Chemoprophylaxis can be safely started at any time within 24 h post-skin closure in major abdominal surgery, without affecting bleeding or VTE risks. This finding encourages the standardization of chemoprophylaxis timing in the postoperative period to pre-defined times during the day to improve workflow efficiency and chemoprophylaxis compliance. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00268-023-06899-5.