risk factors and neonatal outcomes of late onset hyponatremia in preterm infants

Abstract

Introduction: Late-onset hyponatremia (LOH), hyponatremia occurring after two weeks of age with the achievement of full feeding, is the result of a negative sodium balance caused by inadequate salt intake or excessive salt loss due to immature renal or intestinal function in preterm infants. Objectives: The aims of our study were to identify the risk factors for LOH and their influence on neonatal outcomes.

Methods: This was a retrospective cohort analysis of 161 preterm infants younger than 34 weeks of gestation who were born between June 2009 and December 2010 at Seoul National University Hospital. LOH was defined as a sodium level <132 mEq/dL or 133-135 mEq/dL with oral sodium supplementation. For the risk factor analysis, perinatal factors were compared between LOH and non-LOH groups using a multiple logistic regression analysis. For the outcome analysis, the relationships between the risk factors and outcomes were analyzed with simple linear or logistic regressions, and the variables that correlated with the outcome variables were included in multiple linear or logistic regressions. We included gestational age at birth (GA) in all of the models.

Results: LOH occurred in 49 (30.4%) of the studied infants. A lower GA, a shorter duration of parenteral nutrition, the presence of respiratory distress syndrome, the use of furosemide, and feeding with breast milk were significant risk factors for LOH. In terms of neonatal outcomes, the infants with LOH had longer hospital stays and higher risks of bronchopulmonary dysplasia (BPD) and retinopathy of prematurity requiring surgery (ROP). LOH lasting at least seven days was significantly associated with longer hospital stays, moderate to severe BPD, periventricular leukomalacia, and extrauterine growth restriction, regardless of oral sodium supplementation.

Conclusions: LOH was commonly observed in preterm infants

it may be a risk factor for BPD or ROP

and it may be a marker of illness severity. Future research with a larger cohort is needed.