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Hyponatremia in newborns
Last reviewed: 04.07.2025
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Hyponatremia is a serum sodium concentration less than 135 mEq/L. Severe hyponatremia may result in seizures or coma. Treatment of hyponatremia is cautious replacement of sodium with 0.9% sodium chloride solution; 3% sodium chloride solution is rarely required.
[ What causes hyponatremia in newborns?
The most common cause of hyponatremia is hypovolemic dehydration from vomiting or diarrhea (or both), when large gastrointestinal losses are replaced with fluid that contains little or no sodium.
Less common is euvolemic hyponatremia due to impaired ADH secretion and, accordingly, fluid retention. Possible causes of impaired ADH secretion include infections and tumors of the central nervous system. Also, excessive dilution of infant formulas can lead to water intoxication. Hypervolemic hyponatremia develops in conditions of water retention and excessive sodium retention, such as in cardiac and renal failure.
Symptoms of Hyponatremia in Newborns
Symptoms of hyponatremia include nausea and vomiting, lethargy, headache, seizures, and coma; other symptoms include seizures and weakness. Neonates with hyponatremic dehydration may be severely ill because hyponatremia causes a disproportionate decrease in extracellular fluid. Syndromes and manifestations are related to the duration and degree of hyponatremia.
Treatment of hyponatremia in newborns
Hyponatremia is treated with 5% glucose and 0.45-0.9% sodium chloride intravenously in volumes corresponding to the calculated deficit, given for as many days as required to correct the sodium concentration, but not more than 10-12 mEq/(L 24 h) to avoid rapid shift of fluid to the brain. Patients with hypovolemic hyponatremia require volume expansion with salt-containing solutions to correct the sodium deficit (10-12 mEq/kg body weight or even 15 mEq/kg in younger patients with severe hyponatremia) and maintain sodium requirements [3 mEq/(kg 24 h) in 5% glucose]. Patients with symptoms of hyponatremia (eg, lethargy, altered consciousness) require emergency treatment with 3% sodium chloride to prevent seizures or coma.