A 57-year-old woman is evaluated in the emergency department for a 1-week history of swelling and pain in the left leg. She has had two normal pregnancies and no miscarriages. There is no family or personal history of thromboembolic disease. The patient is otherwise healthy.
A proximal deep venous thrombosis is confirmed on ultrasound. Unfractionated heparin is given as an initial bolus followed by a continuous infusion at a dose to prolong the activated partial thromboplastin time to two times the control value. Warfarin, 5 mg/d, is also initiated.
The appropriate treatment for a patient with deep venous thrombosis that is either idiopathic or associated with a transient risk factor is an initial short course of an immediate-acting anticoagulant such as unfractionated heparin, low-molecular-weight heparin, or fondaparinux for at least 5 days. Warfarin should be started at approximately the same time that heparin is administered, and the two drugs should be overlapped until the INR reaches a therapeutic range (>2) measured on two occasions approximately 24 hours apart. This timing allows for further reduction of prothrombin, the vitamin K–dependent factor with the longest half-life (approximately 60 h), which is responsible for much of the antithrombotic effect of warfarin. Usually 5 to 7 days of therapy are required to achieve this therapeutic level. The initial recommended daily warfarin dose is 5 mg, but occasionally 7.5 to 10 mg may be used. Lower doses (2.5 mg) are recommended in the elderly, especially in the setting of malnourishment, liver disease, or recent major surgery.
- Treatment of deep venous thrombosis consists of an immediate-acting anticoagulant such as unfractionated heparin, low-molecular-weight heparin, or fondaparinux for at least 5 days.