The Fluid Therapy Strategy of the Non-dehydrated Patients With Acute Ischemic Stroke.

The investigators previously found that a blood urea nitrogen/creatinine (BUN/Cr) ratio \>15 is an independent predictor of early deterioration after acute ischemic stroke. Another study was conducted to determine whether urine specific gravity, another indicator of hydration status and one more easily obtained, is also an independent predictor of early deterioration or stroke-in-evolution (SIE) in such patients. The investigators also conducted a preliminary study, enrolling ischemic stroke patients with a BUN/Cr ratio \>15 and find daily Bun/Cr based hydration help to decrease post stroke infection rate and improve 3 months functional outcome. In this study, daily urine specific gravity will be used to adjust hydration therapy in ischemic stroke patients with initial Bun/Cr ratio \<15. The primary outcome is the post stroke infection rate in the first 7 days after admission, and secondary outcome is 3 months functional outcome using mRS.