Hypernatremic dehydration due to concentrated infant formula: report of two cases.

Hypernatremic dehydration is a rare but serious clinical condition in newborns and small infants. It is usually caused by diarrhea, improperly prepared infant formula, decreased fluid intake, or exclusive breastfeeding. Symptoms are usually masked until neurological symptoms occur. We report two infants who presented with fever and hypernatremic dehydration caused by concentrating infant formula to alleviate symptoms of constipation, and careless formula preparation due to confusion over spoon sizes, respectively. In the first case, status epilepticus occurred during early treatment, despite close serum sodium monitoring, though the infant was asymptomatic and thriving 4 years after discharge, with no identified neurodevelopmental deficits. The course of treatment was smooth in the second case, and no neurological complications developed. The practice of concentrating infant formula to relieve symptoms of constipation, although temporarily effective, is hazardous to newborns or young infants and can cause hypernatremic dehydration. Spoon sizes supplied with commercial infant formulas (30 mL/spoonful or 60 mL/spoonful) should be unified to avoid mistakes during preparation, especially by inexperienced and teenage mothers.