Urine specific gravity as a predictor of early neurological deterioration in acute ischemic stroke

Lin LC, WC Fann, MH Chou, HW Chen, YC Su, JC Chen. Medical Hypotheses (2011) 77, 11-14.

The authors of this paper have previously suggested that dehydration may be a cause of early deterioration in patients who have suffered an acute ischaemic stroke. This was based on measurement of the blood urea nitrogen/creatinine (BUN/Cr) ratio: they found that a high value ( >15) was an independent predictor of early neurological deterioration.

They therefore aimed in this paper to see if a much simpler method of assessing hydration status – the measurement of urine specific gravity – could be used to identify those patients likely to experience an adverse outcome. They followed a total of 317 patients (43 of whom experienced worsening of neurological symptoms, ie stroke-in evolution (SIE) and 274 who did not) and assessed a wide range of parameters.The only two independent predictors of early deterioration were BUN/Cr >15 and urine specific gravity >1.010. After adjusting for age and gender, those patients with a urine specific gravity >1.010 were 2.78 times more likely to develop SIE (95% Cl = 1.11-6.96; P = 0.030). This study has established two things.

Firstly, it has confirmed the earlier findings that dehydration will increase the likelihood of an adverse outcome in patients who have suffered a stroke: a urine SG of 1.010 is consistent with a rather modest level of dehydration. Secondly, it suggests that a simple urinary measure can identify patients at risk and thus allow early intervention in those individuals.

Abstract

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We previously found that a blood urea nitrogen/creatinine (BUN/Cr) ratio>15 is an independent predictor of early neurological deterioration after acute ischemic stroke, which suggests that dehydration may be a cause of early deterioration. The aim of this study was to determine whether urine specific gravity, which is another indicator of hydration status and one that is more easily obtained, is also an independent predictor of early deterioration or stroke-in-evolution (SIE). Demographic and clinical data were recorded at admission from patients with acute ischemic stroke who were prospectively enrolled from October 2007 to June 2010. We compared patients with and without stroke-in-evolution (based on an increase of 3 points or more points on the National Institutes of Health Stroke Scale within 3 days). Univariate and multivariate statistical analyses were carried out. A total of 317 patients (43 SIE and 274 non-SIE) were enrolled; the first 196 patients comprised the cohort of our previous study. The only two independent predictors of early deterioration or SIE were BUN/Cr>15 and urine specific gravity>1.010. After adjusting for age and gender, patients with a urine specific gravity>1.010 were 2.78 times more likely to develop SIE (95% CI=1.11-6.96; P=0.030). Urine specific gravity may be useful as an early predictor of early deterioration in patients with acute ischemic stroke. Patients with urine specific gravity ≤ 1.010 therefore may have a reduced likelihood of early neurological deterioration.

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