Effect of warfarin on intracranial hemorrhage incidence and fatal outcomes.

Introduction: Avoiding intracranial hemorrhage (ICH) during warfarin therapy is critical but little is known about factors that affect warfarin-related ICH outcomes. We aimed to define the impact of warfarin on ICH incidence rates and to identify baseline clinical characteristics of patients who experienced ICH and factors associated with fatal ICH.

Materials And Methods: The primary outcome of this retrospective cohort study was the incident ICH rate per 10,000 person-years for patients receiving and not receiving warfarin therapy. Cox proportional hazards modeling was used to adjust for potential confounding factors in assessment of the association of warfarin with fatal ICH.

Results: A total of 1348 patients with incident ICH, 259 (19%) who were receiving warfarin therapy, were included. The incident ICH rates were 74/10,000 (warfarin) and 5/10,000 (non-warfarin) person-years (p<0.001). Warfarin patients were older and carried a higher burden of chronic disease. The unadjusted hazard ratio (HR) for fatal ICH was 1.64 (95% confidence interval [CI] 1.31-2.05) for warfarin patients compared to non-warfarin patients. However, the HR was no longer significant after adjustment for confounding variables (1.10; 95% CI 0.84-1.42). An INR greater than 3.5 at presentation doubled the adjusted risk for fatal ICH with warfarin therapy. Subarachnoid and subdural ICHs were less likely to be fatal than other ICH types, and each year increase in age was associated with 4% increased risk of fatal ICH.

Conclusions: Although warfarin use increases the rate of incident ICH, other factors impact the risk of fatal ICH, even among anticoagulated patients.