Hypernatremia during the first week of life in very preterm infants and neurodevelopmental outcomes at 3 to 4 years of age: a cohort study

Hypernatremia is a common electrolyte disorder in both term and preterm infants. Previous studies have suggested a correlation between hypernatremia and short-term complications in preterm infants, such as intraventricular hemorrhage and chronic lung disease. However, the relationship between hypernatremia and neurodevelopmental outcomes is less well understood. This study aimed to assess the association between hypernatremia during the first week of life and neurodevelopmental outcomes at 3–4 years of age in very preterm infants. This single-center, retrospective cohort study analyzed data from preterm infants born at less than 32 weeks of gestation between 2010 and 2020. Infants with peak whole blood sodium levels > 145 mEq/L during the first week of life were included in the hypernatremia group and those with ≤ 145 mEq/L in the non-hypernatremia group. The primary outcome was neurodevelopmental impairment (NDI) at 3–4 years of age, defined as developmental impairment (developmental quotient < 70), cerebral palsy, hearing impairment, or visual impairment. Secondary outcomes were the components of the primary outcome. We conducted Poisson regression analyses with robust variance, adjusting for perinatal confounders. Of 272 infants with neurodevelopmental data, 82 and 190 infants were in the hypernatremia and non-hypernatremia groups, respectively. The median (interquartile range) gestational age and birth weight were 26.4 (25.1–28.0) and 28.7 (26.6–30.3) weeks and 860 (670–1062) and 997 (778–1264) g for infants in the hypernatremia and non-hypernatremia groups, respectively. Infants in the hypernatremia group had a greater incidence of NDI (29.3% vs. 14.7%, adjusted risk ratio RR 1.75, 95% CI 1.08–2.84) and cerebral palsy (8.5% vs. 1.6%, adjusted RR 5.5, 95% CI 1.72–17.63) than those in the non-hypernatremia group. Hypernatremia during the first week of life was associated with an increased risk of NDI at 3–4 years of age in very preterm infants.