Phenytoin exposure is associated with functional and cognitive disability after subarachnoid hemorrhage

Background and Purpose-Phenytoin (PHT) is routinely used for seizure prophylaxis after subarachnoid hemorrhage (SAH), but may adversely affect neurologic and cognitive recovery. Methods-We studied 527 SAH patients and calculated a "PHT burden" for each by multiplying the average serum level of PHT by the time in days between the first and last measurements, up to a maximum of 14 days from ictus. Functional outcome at 14 days and 3 months was measured with the modified Rankin scale, with poor functional outcome defined as dependence or worse (modified Rankin Scale greater than or equal to4). We assessed cognitive outcomes at 14 days and 3 months with the telephone interview for cognitive status. Results-PHT burden was associated with poor functional outcome at 14 days (OR, 1.5 per quartile; 95% CI, 1.3 to 1.8; P<0.001), although not at 3 months (P=0.09); the effect remained (OR, 1.6 per quartile; 95% CI, 1.2 to 2.1; P<0.001) after correction for admission Glasgow Coma Scale, fever, stroke, age, National Institutes of Health Stroke Scale greater than or equal to10, hydrocephalus, clinical vasospasm, and aneurysm rebleeding. Seizure in hospital (OR, 4.1; 95% CI, 1.5 to 11.1; P=0.002) was associated with functional disability in a univariate model only. Higher quartiles of PHT burden were associated with worse telephone interview for cognitive status scores at hospital discharge (P<0.001) and at 3 months (P=0.003). Conclusions-Among patients treated with PHT, burden of exposure to PHT predicts poor neurologic and cognitive outcome after SAH.