Hyponatremia in Kids: Caused by Supplemental Fluid?

Author: Jeannette Y. Wick, RPh, MBA, FASCP

Hospitalized children were likely to develop hyponatremia after receiving either hypotonic or isotonic intravenous fluids, a study found.

Hyponatremia is a common occurrence among hospitalized children; up to half of them experience this electrolyte imbalance. For some, the consequences are serious and can include adverse central nervous system events and, in rare cases, death. The risk of hyponatremia is a key reason why clinicians avoid administering maintenance hypotonic solutions intravenously to children.
 
A team of researchers from Stanford University School of Medicine set out to evaluate whether administration of hypotonic fluids is associated with a greater risk for hyponatremia (serum sodium level less than 135mEq/L) in hospitalized children than administration of isotonic fluids. They reviewed all hospitalizations at Lucile Packard Children’s Hospital at Stanford between April 2009 and March 2011. The researchers identified 1048 children who had normal serum sodium levels at admission and received either hypotonic or isotonic intravenous maintenance fluids within 24 hours of admission. Their results were published online on August 30, 2013, in the Journal of Pediatrics.
 
Overall, hyponatremia was common regardless of maintenance fluid tonicity. The results showed that 260 (38.6%) children who received hypotonic fluids developed hyponatremia, compared with 104 (27.8%) children who received isotonic fluids. After controlling for multiple factors, the researchers confirmed that patients receiving hypotonic fluids were more likely to develop hyponatremia. Patients who received hypotonic fluids were younger than those who received isotonic fluids, but the difference remained significant even after adjusting for intergroup differences and potential confounders.
 
Previous studies have tended to focus on patient populations at heightened risk of hyponatremia, such as those who are critically ill or have undergone surgical procedures. This study’s results extend this association across the entire spectrum of pediatric inpatient disease. The findings are also in line with several studies demonstrating that hyponatremia is common among hospitalized children, as well as studies finding that hyponatremia is more common in patients receiving hypotonic fluids than in those receiving isotonic fluids.
 
The authors note a few limitations. There were small intergroup differences between patients who received hypotonic and isotonic fluids, and the study was not designed to assess the relative benefit of isotonic fluids. It is also possible that the analysis methods used didn’t adequately control for severity or type of illness. In addition, the study could not determine the appropriateness of fluid volume administered upon hospital admission, making it impossible to assess the impact of fluid volume on the development of hyponatremia.
 
The authors suggest that future studies designed to determine optimal fluid strategies in hospitalized children should aim to identify additional risk factors for hyponatremia, examine alternative approaches to reduced maintenance fluid volumes, and assess the ramifications of greater use of isotonic fluids.

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