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J Thromb Haemost. 2006 Nov;4(11):2384-90. Epub 2006 Aug 1.

Prolonged prophylaxis with dalteparin to prevent late thromboembolic complications in patients undergoing major abdominal surgery: a multicenter randomized open-label study.

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Department of Surgery, Bispebjerg Hospital, University of Copenhagen, Copenhagen, Denmark.



Patients undergoing major abdominal surgery carry a high risk of venous thromboembolism (VTE), but the optimal duration of postoperative thromboprophylaxis is unknown.


To evaluate the efficacy and safety of thromboprophylaxis with the low molecular weight heparin (dalteparin), administered for 28 days after major abdominal surgery compared to 7 days' treatment.


A multicenter, prospective, assessor-blinded, open-label, randomized trial was performed in order to evaluate prolonged thromboprophylaxis after major abdominal surgery. In total, 590 patients were recruited, of whom 427 were randomized and received at least 1 day of study medication, and 343 reached an evaluable endpoint. The primary efficacy endpoint was objectively verified VTE occurring between 7 and 28 days after surgery. All patients underwent bilateral venography at day 28.


The cumulative incidence of VTE was reduced from 16.3% with short-term thromboprophylaxis (29/178 patients) to 7.3% after prolonged thromboprophylaxis (12/165) (relative risk reduction 55%; 95% confidence interval 15-76; P=0.012). The number that needed to be treated to prevent one case of VTE was 12 (95% confidence interval 7-44). Bleeding events were not increased with prolonged compared with short-term thromboprophylaxis.


Four-week administration of dalteparin, 5000 IU once daily, after major abdominal surgery significantly reduces the rate of VTE, without increasing the risk of bleeding, compared with 1 week of thromboprophylaxis.

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