CURRENT CONCEPTS IN ANTICOAGULANT-THERAPY

An understanding of the international normalized ratio (INR)-which was developed to standardize reporting of the prothrombin time (PT) and p rovide consistent regulation of anticoagulation-is important, The reco mmended therapeutic range for the INR (which is calculated from the pa tient's PT, a mean control PT, and the international sensitivity index ) for oral anticoagulant treatment of most conditions is 2.0 to 3.0. I n patients with mechanical cardiac val, es, the INR should be at least 2.5 to 3.5. A common cause for progression of venous thromboembolic d isease and treatment failure is inadequate heparinization during the f irst day of treatment, Therefore, an intravenous bolus of 5,000 to 10, 000 U of heparin should be administered before a maintenance infusion is initiated, Also during the first day of treatment, warfarin therapy can be implemented, Overlap treatment with heparin and warfarin for 4 or 5 days is recommended, Low-molecular-weight heparins, a new class of anticoagulants, have been shown to be more effective than standard heparin in preventing venous thrombosis in orthopedic surgical patient s, but at a higher cost, Patients with mechanical cardiac valves who a re receiving anticoagulant therapy and are scheduled for noncardiac op erations must have a risk-to-benefit assessment of the need for contin uous anticoagulation performed preoperatively. Many of these patients can safely discontinue warfarin therapy for several days as outpatient s before the surgical procedure, Preoperative heparin therapy and warf arin withdrawl in the hospital are recommended only for those patients with cardiac valves at high risk for systemic embolization (with a mi tral valve prosthesis, cardiomyopathy, or previous thromboembolism). T he concurrent use of certain drugs or presence of comorbid conditions can predispose to hemorrhagic complications of anticoagulant therapy, Discontinuation of warfarin treatment, administration of vitamin K, or replacement of vitamin It-dependent coagulation factors with transfus ion of fresh-frozen plasma will reverse the anticoagulant effects of w arfarin.