Incidence of hyponatremia in children with gastroenteritis treated with hypotonic intravenous fluids

Hypotonic saline solutions have been used for over five decades to treat children with diarrheal dehydration. However, concern has recently been raised about the potential for iatrogenic hyponatremia as a result of this therapy. We reviewed the medical records of 531 otherwise healthy children with gastroenteritis who had been admitted to the hospital for intravenous fluid therapy. We retrospectively collected data on 141 of these children who had received two serum electrolytes (one upon admission and the other 4–24 h thereafter). The remaining 390 children were excluded because their charts lacked the required data. We analyzed data in 124 of these 141 patients whose initial serum sodium (Na) level was between 130–150 mEq/l and excluded 17 patients whose admission serum sodium fell outside this range. All patients were treated with intravenous hypotonic fluids (5% dextrose in 0.2% saline, n = 4; 5% dextrose in 0.3% saline, n = 102; 5% dextrose in 0.45% saline, n = 18 patients) as maintenance fluid therapy or maintenance fluid plus deficit therapy; 100 of these children had received an initial saline bolus of 21.05 ± 8.5 ml/kg upon admission. The serum Na level decreased by 1.7 ± 4.3 mEq/l in the whole group. Of the 97 children with isonatremia (Na 139.5 ± 2.7 mEq/l) on admission, 18 (18.5%) developed mild hyponatremia (Na 133.4 ± 0.9 mEq/l, range 131–134), with a decrease in serum Na of 5.7 ± 3.1 mEq/l, and 79 remained isonatremic (Na 138.3 ± 2.7 mEq/l), with a decrease in serum Na of 1.8 ± 3.4 mEq/l (p < 0.0005). There was no significant difference in type, rate, or amount of intravenous fluid or saline bolus (26.1 ± 10.4 vs. 20.2 ± 8.6 ml/kg, respectively) administered in these two groups. Children who became hyponatremic were older (5.8 ± 2.7 years) than those who remained isonatremic (2.8 ± 3.1 years) (p < 0.0005), but there was no statistical difference in gender, degree of dehydration, and severity of metabolic acidosis between the two groups. Although serum Na increased by 3.9 ± 2.5 mEq/l in 19 patients with mild hyponatremia upon admission (Na 132.8 ± 1.3 to 136.7 ± 2.6 mEq/l) and 73% of these became isonatremic, hypotonic saline solutions have the potential to cause hyponatremia in children with gastroenteritis and isonatremic dehydration.