Hypernatremia is typically defined as a serum or plasma sodium greater than 150 mEq/L. Although pediatric hypernatremia is an uncommon electrolyte abnormality, there can be significant neurologic injury in patients with severe hypernatremia, especially those with acute and rapid changes in serum sodium.
The etiology, clinical findings, diagnosis, and evaluation of pediatric hypernatremia are reviewed here.
The true incidence of pediatric hypernatremia is unknown, as published data are based on hospitalized children.
As an example, a Scottish study reported an overall incidence of hypernatremia (defined as a plasma sodium >150 mEq/L) of 0.04 percent for all pediatric hospitalizations in pediatric patients over two weeks of age over a study period from 1996 to 2006 . However, the risk of hypernatremia was 10 times greater in neonates less than two weeks of age, with an incidence of 0.4 percent. Neonatal hypernatremia was almost exclusively seen in breastfed infants with excessive weight (water loss). Of note, the incidence of neonatal hypernatremia in breastfed infants was higher than reported in previous studies (0.03 to 0.07 percent) (see "Initiation of breastfeeding", section on 'Excessive weight loss'). In older patients between two weeks and 17 years of age, the most common cause of hypernatremia on admission was excess water loss due to gastroenteritis or systemic infection. However, in this cohort, it was more common for hypernatremia to develop during hospitalization, particularly in patients with systemic infection or those who underwent cardiac surgery. In addition, approximately one-third of the patients had an underlying neurologic condition.
In an earlier study from a tertiary children’s hospital in Texas from 1992 to 1994, hypernatremia (defined as a serum sodium greater than 150 mEq/L) was detected in 1.4 percent of sodium values in a laboratory database, but only 0.2 percent of patients were discharged with a diagnosis of hyperosmolality due to hypernatremia . Of the 68 children with a final discharge diagnosis of hyperosmolality/hypernatremia, two-thirds of the children developed hypernatremia during hospitalization, and the most common cause of hypernatremia was inadequate fluid intake.