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Hyponatremia in children

Michael J Somers, MD
Avram Z Traum, MD
Section Editor
Tej K Mattoo, MD, DCH, FRCP
Deputy Editor
Melanie S Kim, MD


Hyponatremia is defined as a serum or plasma sodium less than 135 mEq/L. Hyponatremia is among the most common electrolyte abnormalities in children. Drops in sodium level can lead to neurologic findings and in severe cases significant morbidity and mortality, especially in those with acute and rapid changes in plasma or serum sodium.

The etiology, clinical findings, diagnosis, and evaluation of pediatric hyponatremia are reviewed here. Hyponatremia in adults is discussed separately. (See "Causes of hyponatremia in adults" and "Overview of the treatment of hyponatremia in adults" and "Diagnostic evaluation of adults with hyponatremia".)


The true incidence of pediatric hyponatremia is unknown, as published data are based on hospitalized children. As examples, the reported incidence of hyponatremia was 17 percent of children at the time of hospital admission in Japan, which was higher in febrile children [1]. The incidence increased to 45 percent in an Italian study in children with pneumonia [2]. This is most likely due to the release of antidiuretic hormone (ADH) associated with a number of clinical conditions that result in hospitalization. These include hypovolemia, fever, head injury, central nervous system (CNS) infections, and respiratory disorders (eg, pneumonia and respiratory syncytial virus bronchiolitis) [1,3].

In addition, in-hospital interventions, such as recent surgery (which is associated with ADH release), and the administration of hypotonic intravenous solutions, may contribute to the development of hyponatremia [4]. The effect of administered hypotonic intravenous solution on the development of hyponatremia, especially in children with persistent ADH release, was illustrated by the following studies:

In a study from the United States of 1048 children who had normal serum sodium levels at the time of presentation, overall 35 percent of the cohort developed hyponatremia [5]. Patients who received hypotonic fluids were more likely to develop hyponatremia than those who received isotonic fluids (39 versus 28 percent). Additional identified risk factors for hyponatremia included admitting diagnoses of a cardiac or hematologic/oncologic condition, and surgical admission.

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Literature review current through: Dec 2017. | This topic last updated: Nov 11, 2016.
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