Incidence and Risk Factors for Hyponatremia in Critically Sick Neonates Receiving Hypotonic Intravenous Maintenance Fluid: A Prospective Observational Study

Objectives Hyponatremia is prevalent among sick neonates in the neonatal intensive care unit. The use of hypotonic fluids for intravenous maintenance therapy (IV-MF) in neonates lacks strong evidence and follows guidelines set for children. Recent findings suggest a shift from hypotonic to isotonic solutions in pediatric IV-MF. This study aims to find out the incidence and risk factors for developing hyponatremia in sick neonates requiring intravenous fluids at the time of admission. Methods This prospective observational study involved sick neonates requiring IV-MF therapy. Neonates with acute kidney injury, renal anomalies, or on diuretics were excluded. Serum and urinary sodium levels were measured serially. Characteristics and risk factors of neonates were compared between hyponatremia and normonatremia groups using univariate and multivariate logistic regression. Results Out of 200 neonates, 60 (30%) were preterm, 46 (23%) were small for gestational age, with a male-to-female ratio of 1.13:1. Hypoxic ischemic encephalopathy (HIE) and sepsis were the most common reasons for admission. One fifth of all enrolled cases had hyponatremia on presentation, 8.1% developed hyponatremia on day 3, 14.4% on day 5, and 18.5% on day 7. The mean (SD) urinary sodium excretion on days 3, 5, and 7 were 37.64 ± 12.69 mmol/L, 36.56 ± 13.94 mmol/L, and 31.83 ± 11.75 mmol/L, respectively. Preterm (<32 weeks) neonates, those with necrotizing enterocolitis (NEC) or moderate-to-severe birth asphyxia, had significantly higher odds for developing hyponatremia ( P < .05). Conclusion Critically ill neonates receiving hypotonic IV fluids have a high prevalence of hyponatremia, especially those with extreme prematurity, NEC, and HIE, necessitating frequent electrolyte monitoring or the use of isotonic fluids.