ABSTRACT
Second, from the perspective of clinicians and patients, the incidence of venous thromboembolism is markedly reduced through the prophylactic use of low-dose unfrac tionated heparin, which prevents thrombus formation by inhibiting thrombin activity via cofactor antithrombin III; low-molecular-weight heparin, which prevents thrombus forma tion primarily by inhibition of factor Xa; or warfarin, which inhibits the proper synthesis of vitamin K-dependent coagulation factors II, VII, IX, and X. Aspirin is much less effective. Mechanical measures-such as intermittent external pneumatic compression devices for the calf or leg, which prevents venous stasis and activates fibrinolysis, or made-to-measure elastic compression stockings-have also been shown to be effective. The evidence fa voring these prophylactic measures is more extensive for patients with surgical problems than for those with medical ones.
