Treatment and prevention of venous thromboembolism.

Where available, low-molecular-weight heparin (LMWH) is the recommended approach for initial management of venous thromboembolism. When unfractionated heparin is administered, one of the cited heparin nomograms should be used to ensure that the heparin dose is sufficient to rapidly produce heparin levels in the therapeutic range for all patients. Because of the varying sensitivities of thromboplastins, each laboratory should correlate the activated partial thromboplastin time results with heparin's therapeutic range, which will correspond to 0.35 to 0.70 U of heparin/ml blood when using the antifactor Xa assay. Constant vigilance and a high level of suspicion are necessary to establish the clinical diagnosis of heparin-induced thrombocytopenia, and to institute appropriate therapy. When administering warfarin therapy, physicians should be aware of the sensitivity of the thromboplastin being used to provide the international normalized ratio (INR). To ensure that the patients are maintained within the target therapeutic range for INR (in most cases 2.0 to 3.0), the INR should be determined frequently, and the warfarin dosage should then be adjusted appropriately. Patients with an acute episode of venous thromboembolism should receive warfarin therapy for at least 3 months. At the present time, it is reasonable to treat the first recurrence with oral anticoagulants for 12 months and to indefinitely treat more than one recurrence. All patients at moderate to high risk for developing venous thromboembolism should receive prophylaxis. The approaches of proven value include low-dose heparin, LMWH, oral anticoagulants, and intermittent pneumatic compression.