[Thromboembolism prophylaxis with low molecular weight heparin in abdominal surgery]

The effect of low-molecular weight (LMW) heparin fragment (one injection of 1500 aPTT [activated partial thromboplastin time]-U/24 h)--group 1--was compared with unfractionated (UF) heparin (3 x 5000 IU/24 h)--group 2--in a randomized prospective double-blind trial of 404 patients (202 patients in each group), aged 50 years or older, undergoing abdominal surgery. The two groups were well matched for thromboembolic risk factors. The first subcutaneous injection was made two hours preoperatively; postoperative injections continued for at least seven days. The radiofibrinogen test served as the test criterion. If positive, phlebography and lung sequence scanning were performed. On complete prophylaxis the thrombosis rate was nearly identical in the two groups--10.8% vs 11.4%. No pulmonary emboli were detected in either group if correctly treated. There was no significant difference between the two groups with respect to peroperative blood loss, re-operation rate and wound haematoma rate. But there was a significantly higher number of injection haematomas in group 2. These results suggest that a single daily injection of 1500 aPTT-U LMW heparin provides effective prophylaxis against postoperative venous thromboembolism.