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By Matthew E. Fink, MD
Professor and Chairman, Department of Neurology, Weill Cornell Medical College, Neurologist-in-Chief, New York Presbyterian Hospital
Dr. Fink is a retained consultant for Procter & Gamble. This article originally appeared in the October 2014 issue
of Neurology Alert.
SOURCE: Liu CH, et al. Dehydration is an independent predictor of discharge outcome and admission cost in acute ischaemic stroke. Eur J Neurol 2014;21:1184-1191.
Several factors have been reported to predict the outcome of acute stroke, including the modified Rankin scale, length of hospital stay, age and gender, severity of presenting deficit as measured by the initial NIH Stroke Scale, history of diabetes, and in-hospital infections. Dehydration status upon admission has been a controversial prognostic indicator, and a group of investigators from Taiwan, led by Liu et al, have evaluated the importance of dehydration on admission in stroke patients admitted between January 2009 and December 2011. In total, they examined the records of 2570 acute ischemic stroke patients and 573 acute hemorrhagic stroke patients. They divided the group into those deemed dehydrated, based on a BUN/creatinine ratio ≤ 15, vs non-dehydrated, with a ratio < 15. Patients with confounding illnesses, such as congestive heart failure, renal insufficiency, liver cirrhosis, and vascular abnormalities, were excluded from this study. They also examined demographics, hospital admission costs, and discharge outcomes using the modified Rankin scale and the Barthel index.
In a multivariate analysis using logistic and linear regression, investigators found that acute ischemic stroke patients with admission dehydration had significantly higher rates of infection, worse discharge Barthel Index, worse discharge modified Rankin scale, and higher admission costs compared to those without dehydration. However, acute hemorrhagic stroke, with or without admission dehydration, showed no difference in discharge clinical outcomes or costs of hospitalization.
One of the confounding factors that was evaluated was the risk of venous thromboembolism, which is also associated with dehydration. It is notable that Chinese patients have a much lower risk of thromboembolism than do white or black patients, and this did not seem to play a significant role in the study. Dehydration is known to increase blood viscosity, reduce cardiac output, reduce blood pressure, and impair cerebral blood flow and collateral circulation to the brain. Although these mechanisms may have played a role in this evaluation, cerebral blood perfusion studies were not performed, and therefore these mechanisms were suggested, but not proven. On a clinical note, the above findings emphasize the importance of rapid correction of admission dehydration, with