3 To address this uncertainty, we randomized 355 nonbleeding warfarin-treated patients whose INR was >5.0 and 5.0 and 4.0, oral vitamin K (in doses between 1 and 2.5 mg) will lower the INR to between 1.8 and 4.0 within 24 hours. 2 However, an earlier observational study of 114 asymptomatic patients taking warfarin with an INR >6.0 managed without vitamin K reported major bleeding in 5 patients (4.4% 95% confidence interval, 1.4%–9.9%) during 14 days of follow-up. In one observational cohort of 1104 warfarin-treated asymptomatic patients with a single INR value between 5.0 and 9.0 (90% of whom were managed with simple warfarin withdrawal), only 0.96% experienced major hemorrhage within 30 days. However, there is uncertainty about the short-term risk of major bleeding in such a patient. 1 Low-dose oral vitamin K is often considered in such situations because INR elevations like the one described here can be quite alarming to both the patient and the clinician. This patient's INR will return to the therapeutic range more quickly if she receives low-dose oral vitamin K (as opposed to simple warfarin withdrawal). For an asymptomatic patient whose INR is >5, warfarin should be withheld for at least 1 dose, and close follow-up monitoring should be arranged. Irrespective of whether a cause for the INR increase can be identified, the patient should be interviewed and examined to ensure she is not bleeding.
In this case, the antibiotic is the likely cause, but it is not unusual for an INR measurement to exceed 3.0 without explanation. Supratherapeutic INR values are common in warfarin-treated patients. Her international normalized ratio (INR) is reported as 8.6. She has recently begun taking trimethoprim/sulfamethoxazole. She takes warfarin for atrial fibrillation. Customer Service and Ordering InformationĬase Presentation: A 74-year-old woman presents to the emergency department with bruising.Stroke: Vascular and Interventional Neurology.Journal of the American Heart Association (JAHA).Circ: Cardiovascular Quality & Outcomes.Arteriosclerosis, Thrombosis, and Vascular Biology (ATVB).
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