Optimal Timing of Perioperative Chemical Thromboprophylaxis in Elective Major Abdominal Surgery

To investigate the effect of timing of chemoprophylaxis on VTE and bleeding rates in patients undergoing major abdominal surgery.Postoperative bleeding and venous thromboembolisms (VTE) incur significant morbidity, mortality and healthcare costs. Chemoprophylaxis is used routinely to prevent VTEs but increases bleeding risk. The perioperative timing of chemoprophylaxis initiation may influence both VTE and bleeding risks. The optimal window for commencing chemoprophylaxis in the perioperative period is unclear.MEDLINE, EMBASE, Cochrane Library, and Web of Science databases were searched using PRISMA guidelines. Randomized trials and cohort studies published between 01 January 2000 to 10 May 2022 which reported on chemoprophylaxis timing as well as the incidence of VTE and bleeding following elective abdominal surgery were meta-analyzed.From 6,175 studies, 14 (24,922 patients) were meta-analyzed. Bariatric (4 studies), antireflux (1 study), hepato-pancreatic-biliary (5 studies), colorectal (1 study), ventral hernia (1 study), and major intra-abdominal surgeries (2 studies) were included. Chemoprophylaxis was initiated before skin closure in 10,403 patients, and postoperatively in 14,519 patients. Both symptomatic (RR 0.81, 95% CI 0.45-1.43, P=0.460) and overall (RR 0.74, 95% CI 0.45-1.24, P=0.250) VTE rates were comparable between study groups. Compared with postoperative chemoprophylaxis, early usage increased the risk of all bleeding (RR 1.56, 95% CI 1.13-2.15, P=0.007), major bleeding (RR 1.63, 95% CI 1.16-2.28, P=0.005), blood transfusion (RR 1.48, 95% CI 1.24-1.76, P0.001) and reintervention (RR 1.94, 95% CI 1.19-3.18, P=0.008).Our findings advocate for initiating chemoprophylaxis postoperatively in elective abdominal surgery to minimize bleeding risk without compromising VTE protection.