A comparative, double-blind, randomised trial of a new second generation LMWH (Bemiparin) and UFH in the prevention of post-operative venous thromboembolism

A randomised, prospective, double-blind trial was performed, to compare the safety and efficacy of a new low-molecular-weight heparin (LMWH) Bemiparin and standard unfractionated heparin (UFH), for the prophylaxis of postoper ative venous thromboembolism. 300 patients scheduled to undergo elective hi p arthroplasty were included. The principal outcome measures were the incid ence of thromboembolic events and bleeding complications. 149 patients rece ived 3,500 anti-Xa IU of bemiparin plus a placebo injection daily and 149 p atients received 5,000 IU of UFH twice a day. The two groups were similar with respect to factors likely to affect the ri sk of developing post-operative venous thromboembolism (VTE) and risk of bl eeding events. During the post-operative period, 34 patients developed VTE complications; 9 (7.2%) in the bemiparin group and 25 (18.7%) in the UFH gr oup. VTE in the two groups was statistcally significant (OR of 2.96; 95% CI 1.32-6.62 and p = 0.01). There were no significant differences in the frequency of bleeding complica tions: major bleeding requiring discontinuation of prophylaxis, (OR 1.21; 9 5% CI 0,36-4.05; p = 1.00), the measured median operative blood loss (p = 0 .77) or the median postoperative drain loss (p = 0.97), and the number of p atients who developed wound haematoma (OR 0.87, 95% CI 0.31-2.46: p = 1.00) . A comparison of coagulation parameters on the preoperative day with post-op erative day 2 +/- 1, day 6 +/- 1 and day of discharge showed a significantl y higher AT concentration, anti-factor Xa activity and TFPI levels in the b emiparin group when compared with UFH. This study demonstrates that bemiparin. in a single daily subcutaneous dose or 3,500 anti-Xa IU in high risk patients undergoing hip arthroplasty is m ore effective than UFH administered twice daily at a dose of 5,000 IU in th e prevention of postoperative VTE. Both agents are equally safe.