Mild elevations of international normalized ratio at hospital Day 1 and risk of expansion in warfarin-associated subdural hematomas.

OBJECT: A primary goal in the treatment of patients with warfarin-associated subdural hematoma (SDH) is reversal of coagulopathy with fresh-frozen plasma. Achieving the traditional target international normalized ratio (INR) of 1.3 is often difficult and may expose patients to risks of volume overload and of thromboembolic complications. This retrospective study evaluates the risk of mild elevations of INR from 1.31 to 1.69 at 24 hours after admission in patients presenting with warfarin-associated SDH.

METHODS: Sixty-nine patients with warfarin-associated SDH and 197 patients with non-warfarin-associated SDH treated at a single institution between January 2005 and January 2012 were retrospectively identified. Charts were reviewed for patient age, history of trauma, associated injuries, neurological status at presentation, size and chronicity of SDH, associated midline shift, INR at admission and at hospital Day 1 (HD1), concomitant aspirin or Plavix use, platelet count, and medical comorbidities. Patients were stratified according to use of warfarin and by INR at HD1 (INR 0.8-1.3, 1.31-1.69, 1.7-1.99, and ≥ 2). The groups were evaluated for differences the in rate of radiographic expansion of SDH and in the rate of clinically significant SDH expansion resulting in death, unplanned procedure, and/or readmission.

RESULTS: There was no difference in the rate of radiographic versus clinically significant expansion of SDH between patients not on warfarin and those on warfarin (no warfarin: 22.3% vs 20.3%, p = 0.866; warfarin: 10.7% vs 11.6%, p = 0.825), but the rate of medical complications was significantly higher in the warfarin subgroup (13.3% for patients who did not receive warfarin vs 26.1% for those who did; p = 0.023). For warfarin-associated SDH, there was no difference in the rate of radiographic versus clinically significant expansion between patients reversed to HD1 INRs of 0.8-1.3 and 1.31-1.69 (HD1 INR 0.8-1.3: 22.5% vs 20%, p = 1; HD1 INR 1.31-1.69: 15% vs 10%, p = 0.71).

CONCLUSIONS: Mild INR elevations of 1.31-1.69 in warfarin-associated SDH are not associated with a markedly increased risk of radiographic or clinically significant expansion of SDH. Larger prospective studies are needed to determine if subtherapeutic INR elevations at HD1 are associated with smaller increases in risk of SDH expansion.