RT Journal A1 Birkmeyer NO, Finks JF, Carlin AM, et al T1 COmparative effectiveness of unfractionated and low-molecular-weight heparin for prevention of venous thromboembolism following bariatric surgery JF Archives of Surgery JO Archives of Surgery YR 2012 FD November 1 VO 147 IS 11 SP 994 OP 998 DO 10.1001/archsurg.2012.2298 UL http://dx.doi.org/10.1001/archsurg.2012.2298 AB 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.