When bleeding complicates oral anticoagulant therapy. How to anticipate, investigate, and treat.

With use of the International Normalized Ratio (INR), physicians can accurately assess the intensity of anticoagulation in treatment programs and trials. Bleeding is the major complication of oral anticoagulant therapy, and its incidence can be lessened, with no loss of efficacy, by using less intense therapy (INR, 2 to 3). INRs above the target range, marked variability in INRs, newly initiated therapy, previous bleeding, and a serious comorbid condition all constitute significant risk factors. While age over 65 is not a proven risk factor, the elderly are more sensitive to the effects of warfarin and require smaller doses. Meticulous attention should be paid to the concomitant use of any medications that may affect metabolism of warfarin or induce a concomitant qualitative platelet effect (specifically, aspirin and nonsteroidal antiinflammatory drugs) and to dietary modifications that significantly change vitamin K intake. Hematuria or gastrointestinal bleeding should always be assessed, since the chance of finding a clinically significant lesion is good, especially when the INR has been in the therapeutic range. While a minor prolongation of the INR without bleeding may be treated by watchful waiting, vitamin K administration and other therapeutic measures may be necessary in patients who are actively bleeding.