Hyponatremia in hospitalized children.

To determine the frequency, causes, and clinical significance of hyponatremia in hospitalized children, we reviewed the clinical and laboratory data of all hyponatremic children in Texas Children's Hospital over a 12-month period. One hundred sixty-one patients from among 11,702 hospital admissions were found to have hyponatremia, defined as serum sodium value of less than 130 mEq/L, an overall frequency of 1.38%. Sixty-nine patients (43%) had hyponatremia on admission, and 92 patients (57%) had hospital-acquired hyponatremia. Thirty-seven (23%) were previously healthy children, and 124 (77%) had chronic illnesses. Acute gastroenteritis was the leading cause of hyponatremia present on admission, and diuretic therapy was the leading cause of hospital-acquired hyponatremia. Only four patients (2.5%) had a serum sodium concentration of less than 120 mEq/L. Six patients (3.7%) had neurologic impairment on discharge, and 19 patients (12%) ultimately died long after their hyponatremia was corrected. Each patient who had neurologic sequelae and each patient who died had underlying medical conditions which could explain their morbidity and/or mortality. The prognosis appears to be more clearly related to the underlying medical disorder rather than to the hyponatremic state or its correction.