Low Serum Sodium: Devastating Possibilities in Stroke Patients

Acute ischemic stroke patients with hyponatremia have worse stroke scale scores on admission and discharge as well as worse mortality rates in the hospital and at 3-month and 12-month follow-ups.

Acute ischemic stroke is the most common cause of long-term disability in the United States, affecting 795,000 people each year. Low serum sodium levels are a complication of cerebrovascular disease, and researchers have demonstrated that hyponatremic patients with first-ever ischemic stroke had elevated 3-year mortality rates.

In a study published online on August 15, 2013, in the Journal of Stroke and Cerebrovascular Diseases, researchers from the University of Connecticut Health Center and Hartford Hospital examined acute and chronic clinical outcomes after a stroke in patients with hyponatremia. They reviewed all 3585 patients admitted between 2004 and 2011 with the diagnosis of acute ischemic stroke, identifying 565 (16%) patients who were admitted with hyponatremia, defined as having a serum sodium level lower than 135 mmol/L.

The researchers noted that, on admission, patients with hyponatremia had higher scores on the National Institutes of Health Stroke Scale. The researchers then looked at data at discharge and at 3-month and 12-month follow-ups. They found that patients with hyponatremia on admission had significantly higher rates of short-term mortality when defined as either death during the initial hospital stay or a composite of in-hospital death and discharge to hospice. Chronic mortality rates were also higher for patients with hyponatremia on cumulative comparisons of known death at 3-month and 12-month follow-ups.

Overall, the researchers concluded that patients with hyponatremia have more severe stroke scale scores on admission and that their scores worsen during hospitalization. This is the first study to demonstrate that hyponatremia is an independent predictor of acute mortality at 3 months and confirms the higher mortality in patients with hyponatremia at a 12-month follow-up.

The researchers noted that hypertonic saline is widely used to treat patients with other types of strokes, but it has never been studied in ischemic injury, and would be difficult to study as stroke onset is not always easy to predict. They added that larger studies need to be performed to confirm their findings, to further understanding of the mechanisms of injury associated with hyponatremia, and to explore the potential benefit of correction of hyponatremia after acute ischemic stroke.

Ms. Wick is a visiting professor at the University of Connecticut School of Pharmacy and a freelance writer from Virginia.