Comparative effectiveness of unfractionated and low-molecular-weight heparin for prevention of venous thromboembolism following bariatric surgery.

Objective: To evaluate the effectiveness and safety of 3 predominant venous thromboembolism (VTE) prophylaxis strategies among patients undergoing bariatric surgery.

Design: Cohort study.

Setting: The Michigan Bariatric Surgery Collaborative, a statewide clinical registry and quality improvement program.

Patients: Twenty-four thousand seven hundred seventy-seven patients undergoing bariatric surgery between 2007 and 2012.

Interventions: Unfractionated heparin preoperatively and postoperatively (UF/UF), UF heparin preoperatively and low-molecular-weight heparin postoperatively (UF/LMW), and LMW heparin preoperatively and postoperatively (LMW/LMW).

Main outcome measures: Rates of VTE, hemorrhage, and serious hemorrhage (requiring >4 U of blood products or reoperation) occurring within 30 days of surgery.

Results: Overall, adjusted rates of VTE were significantly lower for the LMW/LMW (0.25%; P < .001) and UF/LMW (0.29%; P = .03) treatment groups compared with the UF/UF group (0.68%). While UF/LMW (0.22%; P = .006) and LMW/LMW (0.21%; P < .001) were similarly effective in patients at low risk of VTE (predicted risk <1%), LMW/LMW (1.46%; P = .10) seemed more effective than UF/LMW (2.36%; P = .90) for high-risk (predicted risk ≥1%) patients. There were no significant differences in rates of hemorrhage or serious hemorrhage among the treatment strategies.

Conclusion: Low-molecular-weight heparin is more effective than UF heparin for the prevention of postoperative VTE among patients undergoing bariatric surgery and does not increase rates of bleeding.