Annotation

Hyponatraemia in the newborn Hyponatraemia is common in inpatients and this includes newborns in neonatal intensive care units. Surveys from around the world suggest that up to a third of very low birthweight infants are hyponatraemic in the first week after birth and between 25 and 65 % thereafter (unpub-lished data).1 2 Sodium and water balance How much is known about the causes of hyponatraemia in the newborn? Sodium is the principal electrolyte of extra-cellular fluid. The normal serum concentration in adults ranges from 132–144 mmol/l. A low serum sodium concentration reflects either an excess of water or primary sodium depletion. Water retention may occur with an increased, normal, or reduced total body sodium content