Stroke Alert
October 1, 2014
Stroke Alert
By Matthew E. Fink, MD
Dehydration Is a Poor Prognostic Sign
in Acute Ischemic Stroke Patients
Source: Liu CH, et al. Dehydration is an independent predictor of discharge outcome and admission cost in acute ischaemic stroke. Europ 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 intravenous fluid replacement therapy as quickly as it can be safely administered.
Sodium Intake, Blood Pressure, and CVD ¨C What Is a Neurologist To Advise?
Source: Oparil S. Low sodium intake — cardiovascular health benefit or risk? New Engl J Med 2014;37:677-679.
In the August 14, 2014, issue of the New England Journal of Medicine, three research articles were published addressing the issues of sodium in the diet and its impact on blood pressure and cardiovascular consequences. This is a controversial area and resulted in the Institute of Medicine convening an expert committee to evaluate the evidence for a relationship between sodium intake and health outcomes. The committee concluded that although there was a positive relation between high sodium intake and the risk of cardiovascular disease, results from studies were insufficient to conclude whether a low sodium intake (less than 1.5 g per day) was associated with an increased or reduced risk of cardiovascular disease in the general population. The editorial by Suzanne Oparil, which references the other three articles in the same issue of the journal, reviews the existing evidence, and comes to the conclusion that it is still unclear whether a low sodium diet should be recommended as part of long-term prevention of cardiovascular disease. High sodium intake seems to be associated with elevations in blood pressure and increased cardiovascular events, including stroke, but what is considered to be a moderate range of sodium intake, defined as 3-6 g per day of sodium, may not have any negative effects on overall health. It is just not known. In addition, it appears that increasing the amount of potassium in the diet may have beneficial effects that are separate and independent of the consequences of high or low sodium.
We urge neurologists who are caring for patients at risk for stroke or who have already had a stroke to pay attention to both diet as well as blood pressure treatments, since hypertension continues to be the single most powerful modifiable risk factor for all stroke subtypes. Recommendations regarding optimal diet are uncertain at the present time, and we will need more research-based evidence before we can make recommendations regarding sodium, carbohydrate, or fat intake, as it relates to cardiovascular risk.
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