Low molecular weight heparin prevention of post-operative deep vein thrombosis in vascular surgery.

Ninety-two patients undergoing vascular surgery took part in a controlled clinical trial to study the effectiveness of a new low molecular weight (LMW) heparin for prevention of post-operative deep vein thrombosis. Forty-six patients were treated daily, for 7 days after operation, with a single subcutaneous injection of 15,000 Anti X-activated Factor Units of the new LMW heparin; the remaining 46 patients were treated, for the same period, with 2 daily subcutaneous injections of 5,000 International Units of calcium heparin. Deep vein thrombosis detection was by the radioactive fibrinogen uptake test, performed each day during therapy in all patients. A very low incidence of sub-clinical deep vein thrombosis was observed; in 3 (6.5%) patients in the LMW heparin group and in 4 (8.6%) patients of the calcium heparin group. The results of laboratory investigation showed that the antithrombotic activity (inhibition of Factor Xa) of the LMW preparation was significantly greater than that of calcium heparin, while activated partial thromboplastin time was greater in the calcium heparin group. The new preparation also showed better local tolerance, with less pain on subcutaneous injections.