Comparison of a low molecular weight heparin and unfractionated heparin for the prevention of deep vein thrombosis in patients undergoing abdominal surgery

In a prospective, randomized multicentre trial the efficacy and safety of the low molecular weight heparin (LMWH) fraction Fraxiparin and unfractionated calcium heparin (Calciparin) were compared for the prevention of postoperative deep vein thrombosis. Of 1909 patients included in the trial 1896 underwent abdominal surgery and received either one daily subcutaneous injection of 7500 anti-Xa units Fraxiparin or 5000 units calcium heparin three times a day subcutaneously. Elastic compression stockings were worn by both groups of patients in the postoperative period. Before randomization the patients were stratified in two subgroups with or without malignant disease. To assess the rate of deep vein thrombosis (DVT), 125I-labelled fibrinogen leg scanning was performed daily for 7 postoperative days. Positive results were confirmed by phlebography whenever possible. Venous thrombosis occurred in 27 of 960 patients (2.8 per cent) given Fraxiparin and in 42 of 936 patients (4.5 per cent) given calcium heparin (P = 0.034). The rates of proximal vein thrombosis were 0.4 per cent (4 patients) and 1.4 per cent (13 patients) respectively (P less than 0.05). Pulmonary embolism occurred in 2 of 960 patients (0.2 per cent) treated with Fraxiparin and in 5 of 936 patients (0.5 per cent) treated with calcium heparin. The two treatments were equally well tolerated. Intra- and postoperative blood loss, the number of wound haematomas as well as frequency and volume of transfusions were similar in both groups. The present trial demonstrates that a single daily subcutaneous injection of Fraxiparin is more effective than the established low dose subcutaneous heparin prophylaxis with 5000 units three times per day in preventing postoperative DVT after abdominal surgery in patients wearing compression stockings.