Mini-dose heparin has been shown to be useful in the prophylaxis of postoperative venous thrombosis. Mechanism(s) by which low-dose heparin is/are thought to protect against venous thrombosis include: a. Enhancement of antithrombin III activity b. A decrease in thrombin availability c. Inhibition of platelet aggregation and subsequent platelet release action d. A mild prolongation of activated partial thromboplastin time