Abstract
OBJECTIVE: The aim of this study was to evaluate the incidence of hyponatremia, risk factors, and its effect on mortality in neonates hospitalized in the neonatal intensive care unit (NICU). METHODS: This retrospective study was conducted in the NICU of a university hospital in Türkiye over a seven-month period in 2016. All 527 infants admitted to the NICU during the study period were included in the study. Hyponatremia was defined as a serum sodium level < 135 mEq/L. Demographic data, clinical diagnoses, fluid therapy, diuretic use, and survival outcomes were analyzed. Multivariate logistic regression analysis was used to identify independent risk factors. RESULTS: The incidence of hyponatremia in the cohort was 21.2% (112/527). The incidence was higher in preterm (23.6%) and extremely low birth weight (ELBW) infants (61.1%). Hyponatremia was mild in the majority of cases (79.9%). The average gestational age and birth weight of hyponatremic infants were significantly lower than those of non-hyponatremic ones (p = 0.011 and p = 0.038, respectively). In logistic regression analysis, low gestational age was identified as an independent risk factor for hyponatremia (OR = 0.905, p = 0.031). Respiratory system disorders (55.4%) were the most common accompanying comorbidity. Diuretic use in 31.8% and administration of hypotonic fluids (1/5 normal saline) in 45.2% of babies were common associated factors. Mortality was significantly higher in hyponatremic babies when compared with non-hyponatremic ones (10.7% vs. 2.9%; p = 0.001). CONCLUSION: Hyponatremia is a common and serious condition in the NICU, associated with a significant increase in mortality; with low gestational age being a key independent risk factor. The frequent use of diuretics and hypotonic fluids highlights potential iatrogenic contributions. These findings suggest the need for careful serum sodium monitoring and a re-evaluation of fluid management protocols, especially for vulnerable ELBW preterm infants.