Hypernatremia in Pediatric patients is less common than other electrolyte abnormalities occurring in <1% of hospitalized patients. The most common cause is water loss, either from poor absorption in the cases of vomiting, diarrhea, malabsorption or insensible losses, or via diabetes insipidus. Congenital disorders may cause decreased thirst receptors resulting in inadequate intake. Finally, excess sodium intake can occur via hypertonic fluids, ingestions or hyperaldosteronism or hypercortisolism.
Symptoms are often nonspecific- including fatigue, vomiting, hypertonia or hyperreflexia in lower states, but may result in lethargy, mental status changes or seizures as levels approach and exceed 160mmol/L
Treatment is similar to adults - free water deficit should be calculated:
Total body water (%) x weight (kg) x [(serum Na)/140 - 1]
Total Body Water (TBW) varies by age:
24-31 weeks- 90%
32-35 weeks - 80%
Term - 12 months - 70%
12 months and up - 60%
IV fluids should be started with a goal of decreasing the sodium level by 0.5 mmol/L/h with close monitoring of sodium levels.
References
Brown DH, Paloian NJ. Hypokalemia/Hyperkalemia and Hyponatremia/Hypernatremia. Pediatr Rev. 2023 Jul 1;44(7):349-362. doi: 10.1542/pir.2021-005119. PMID: 37391630.
