Low molecular weight heparin for the prevention of thromboembolism in outpatients immobilized by plaster cast.

In an open, randomized, prospective, interindividual trial, the incidence of thrombosis with (n = 126) and without (n = 127) LMWH prophylaxis once a day was determined in 253 outpatients immobilized in a plaster cast due to an injury of the lower limb. Furthermore, the influence of possible risk factors on the thrombus formation was determined. The histories of the patients were comparable. The average period of plaster cast immobilization was 15.7 days and did not differ between treatment groups. Thrombosis was diagnosed by compression ultrasound; patients with positive findings were investigated by means of ascending phlebography. There were 21 cases of thrombosis in the group without prophylaxis (16.5%) and only six cases of thrombosis (4.8%) with LMWH. This difference is statistically significant (2p < 0.01). Crucial risk factors were age over 30 years, obesity, varicose veins, and fractures. Patients without prophylaxis who had fractures developed DVT in 29% in contrast to 11.3% in patients with soft-tissue injuries. This study shows that LMWH prophylaxis should be mandatory for plaster cast immobilized patients regardless of preexisting risk factors for thromboembolism.