['Dehydration may impair cerebral oxygen delivery and worsen clinical outcome in patients with acute ischemic stroke (AIS). We evaluated if elevated blood urea nitrogen to creatinine ratio (BUN/Cr) as a marker of dehydration was associated with poor clinical outcome in emergency department (ED) patients presenting with AIS.', 'We conducted a prospective cohort study using a stroke registry enrolling all ED patients with AIS from 10/2007 through 6/2009. Poor clinical outcome was defined as death, placement in a nursing home for purposes other than rehabilitation, or hospice within 30 days of ED presentation. A BUN/Cr ratio of ≥15 was considered elevated. (IQR). Logistic regression was performed adjusted for age >64 years, NIHSS >8, diabetes, prior CVA, and coma at presentation reporting odds ratios with 95% confidence intervals.', '324 patients had a final diagnosis of AIS. 163 (50%) were female, 19 (6%) died, 44 (14%) received t-PA, and 89 (27%) had a poor clinical outcome. The median NIHSS, BUN and Cr were 4 (IQR 1-9), 14 mg/dL (IQR 11-21), and 1.02 mg/dL (IQR 0.87-1.27) respectively. The median BUN/Cr was 13.9 (IQR 10.6-18.5). The variables associated with a poor clinical outcome were: high NIHSS OR 6.5 (3.6-11.8), age >64 years OR 2.7 (1.5-5.0), and BUN/Cr ratio of ≥15 OR 2.2 (1.2-4.0).'] Is elevated blood urea nitrogen/creatinine ratio associated with poor outcome in patients with ischemic stroke?