Late hyponatremia: its risk factors in preterm infants and short-term outcome

Background. Prematurity is one of the major health problems and common causes of neonatal mortality. One of the complications of premature infants is hyponatremia. The effect of hyponatremia on the prognosis of preterm infants has not been well studied. This study aimed to evaluate infants with late hyponatremia, its risk factors, and prognosis.

Methods. This descriptive analytical study reviewed preterm infants (<34 weeks) admitted to Al-Zahra or Children’s Hospital in Tabriz for one year (2019). Neonates diagnosed with hyponatremia after the second week were identified and evaluated for risk factors and short-term outcome.

Results. A total of 186 neonates were studied. The mean gestational age of the neonates was 30 weeks (first and third quarters = 29-32 weeks). 101 (54.3%) infants were male. The route of delivery was the cesarean section in 60.7% of cases. Late hyponatremia was present in 50 (26.8 %) infants. Gestational age and birth weight were significantly lower in infants with hyponatremia than in the control group. Multivariate analysis showed that low birth weight, the use of prenatal steroids, and inappropriate weight for gestational age status independently predict the incidence of late hyponatremia. There was a significant relationship between the presence of prolonged late hyponatremia (over 7 days) and bronchopulmonary dysplasia and osteopenia of prematurity. However, no significant association was found between the presence of prolonged late hyponatremia in preterm infants with the length of hospital stay and in-hospital mortality.

Conclusion. Based on the findings of this study, low birth weight, prenatal steroid use, and lack of appropriate weight for gestational age were risk factors for late hyponatremia in preterm infants. Prolonged hyponatremia is associated with bronchopulmonary dysplasia and osteopenia of prematurity