RISK-FACTORS FAR INTRACRANIAL HEMORRHAGE IN OUTPATIENTS TAKING WARFARIN

Objective: To explore the rational use of anticoagulants, especially a mong the elderly, balancing antithrombotic efficacy and risk for hemor rhage. Previous prospective studies have not provided powerful assessm ents of risk factors for intracranial hemorrhage, the dominant complic ation in reversing the anticoagulant decision. Design: Case-control an alysis. Setting: A large general hospital and its anticoagulant therap y unit. Patients: 121 consecutive adult patients taking warfarin who w ere hospitalized with intracranial hemorrhage were each matched to thr ee contemporaneous controls randomly selected from among outpatients m anaged by our hospital anticoagulant therapy unit. Results: 77 patient s had intracerebral hemorrhage (46% fatal) and 44 had subdural hemorrh age (20% fatal). The prothrombin time ratio (PTR) was the dominant ris k factor for intracranial hemorrhage. For each 0.5 increase in PTR ove r the entire range, the risk for intracerebral hemorrhage doubled (odd s ratio, 2.1; 95% CI, 1.4 to 2.9). For subdural hemorrhage, the risk w as unchanged over the PTR range from 1.0 to 2.0 but rose dramatically above a PTR of 2.0 (approximate international normalized ratio, 4.0). Age was the only other significant independent risk factor for subdura l hemorrhage (odds ratio, 2.0 per decade; CI, 1.3 to 3.1). For intrace rebral hemorrhage, age was of borderline significance (odds ratio, 1.3 per decade; CI, 1.0 to 1.6) after controlling for PTR and the two oth er independent risk factors: history of cerebrovascular disease (odds ratio, 3.1; CI, 1.7 to 5.6) and presence of a prosthetic heart valve ( odds ratio, 2.8; CI, 1.3 to 5.8). Conclusions: The results emphasize t he importance of maintaining the prothrombin time ratios under 2.0 and the need for especially careful use of warfarin in the elderly.