Thromboprophylactic effect of low molecular weight heparin started in the evening before elective general abdominal surgery: a comparison with low-dose heparin.

A prospective randomized double-blind trial was performed comparing conventional low-dose heparin with a LMWH fragment (Kabi 2165, Fragmin) for thromboprophylaxis in elective general abdominal surgical patients. The first dose of the fragment was given in the evening before surgery, and thereafter every evening. There were 1002 analyzable patients, 826 having received correct prophylaxis. Sixty three percent of the patients were operated on for malignant diseases. The frequency of DVT was significantly reduced among patients with correct prophylaxis with the heparin fragment (9.2 to 5.0%, p = 0.02). In patients with malignancies the reduction was from 11.2 to 6.4% (p = 0.06). The frequency of bleeding was 6.7% among the heparin fragment patients and 2.7% among the patients given conventional heparin (p = 0.01). The corresponding frequencies for patients with malignancies were 3.2 and 2.8%, respectively (p = 0.28). All bleedings were minor and of no clinical significance. Local pain at the injection site was reported significantly less often among patients with the fragment. Twenty patients died, 13 with malignant disease, mortality being the same in the two groups. It is concluded that heparin fragment administered in the evening before surgery and then every evening is a practically acceptable alternative to prevent postoperative DVT in patients undergoing elective abdominal surgery, also when the histology shows malignancy. Thus, the advantages of using LMWH compared with conventional low-dose heparin are simplified administration routines, better thromboprophylactic effect, and less local pain at injection sites. A disadvantage is the slight increase in hemorrhagic side effects, all of minor clinical importance and not seen in patients undergoing surgery for malignancy.