[INTERNATIONAL NORMALIZED RATIO VALUES AND HEMORRHAGE IN HOSPITALIZED PATIENTS STARTING WARFARIN THERPY: AN OBSERVATIONAL STUDY].

ABSTRACT

INTRODUCTION: Vitamin K antagonist (VKA) therapy is challenging because of the narrow therapeutic range, and the influence of numerous factors on the international normalized ratio (INR). During the beginning of warfarin treatment, INR must be assessed regularly in order to optimize treatment and minimize the risk for hemorrhage. In this study we examined the laboratory and clinical outcomes of a cohort of hospitalized patients starting warfarin treatment. AIMS: To document the rate of patients with supra-therapeutic INR values and the rate of major hemorrhage, during the first month after starting warfarin. METHODS: A prospective observational study of all patients admitted to Meir Medical Center starting warfarin treatment during a 3-month period. Baseline demographics, clinical data, warfarin dose, INR levels and bleeding events were documented. Patients were followed for 30 days after starting treatment with warfarin. RESULTS: Fifty-seven patients who started VKA therapy were identified during the study period. The mean age was 71.2±13.1 years. Atrial fibrillation was the indication for treatment in 63.2% of patients, deep vein thrombosis in 19.3%, pulmonary embolus in 10.5% and other indications in 7% of patients. In the first 30 days of treatment, 60% of the patients had at least one INR value of >3. Of these patients, half had an INR of above 5. The number of concomitant medications were associated with INR values of >3. Arab patients tended to have a higher INR. Of note, there were 5 cases (8.8%) of major hemorrhage, which occurred with INR values ranging from 3.29 to >10, 4 of these patients were treated concomitantly with Aspirin. CONCLUSIONS: In this cohort of hospitalized patients starting warfarin therapy, excessive INR values were commonly encountered. There was a significant incidence of major hemorrhage among the patients. Further studies to define risk factors for elevated INR values and hemorrhage in hospitalized patients are needed.