[Water intoxication with hyponatremia and cramps in the newborn period]

Acute water intoxication with hyponatraemic convulsions has been described several times in children less than two years old. We describe a two-day-old boy who developed hyponatraemia with convulsions because of water intoxication during his stay in the maternity ward. It was a hot day, and the baby was observed to sweat abundantly. The mother therefore breast fed him at frequent intervals and in addition offered him plain water, which he drank eagerly, approximately 350 ml in the course of a few hours. He then developed convulsions with bilateral clonic flexion movements of the arms, and serum sodium concentration was 113 mmol/l (114 on repeat). He was treated with diazepam and phenobarbitone and 20 mmol NaCl as slow infusion, and serum Na was 135 mmol/l after 20 hours. During treatment he passed large amounts of dilute urine and lost 110 g of weight. No abnormal loss of salt was found, and follow-up for six months has been uneventful. Neonates are at risk of developing hyponatraemia and convulsions when offered large amounts of electrolyte poor solutions, especially during hot weather.