Stepwise Anticoagulation with Warfarin for Prevention of Intravenous Catheter Thrombosis

Warfarin is the most commonly used anticoagulant for prevention and therapy of thrombosis. Warfarin is a vitamin K antagonist and inhibits synthesis of clotting factors II, VII, IX, and X, and anticoagulant proteins C and S. Whereas there is extensive information about the efficacy of warfarin and target International Normalized Ratio (INR) for patients with artificial heart valves, atrial fibrillation, pulmonary emboli, deep venous thrombosis, and lupus anticoagulant, there is little in the literature on the role of warfarin in maintaining the patency of hemodialysis catheters. Much more is reported about the value of minidose warfarin in maintaining the patency of infusion catheters. Many centers have tried low-dose warfarin (1 mg per day), and found this not to be effective in preventing catheter thrombosis in many patients. Although most support the use of warfarin following catheterproblems, individual units have their own guidelines, with doses ranging from 2 mg per day (normal INR) to formal systemic anticoagulation with INR from 1.5 to 3.0. Stepwise anticoagulation with warfarin is emerging as useful in preventing catheter-associated thrombosis. With this method, patients are placed on low-dose warfarin after the first clotting episode. With each subsequent episode, the dose is increased, raising INR by 0.5 until clotting episodes do not recur. Warfarin doses similar to those in patients with artificial heart valves have been used in selected patients (target INR 3.0 - 4.0) to prevent clotting.