Epidemiology of early onset hyponatremia in extremely preterm neonates: A retrospective observational study.

BackgroundExtremely preterm neonates undergo significant serum sodium (Na) changes in the first few days after birth. The objectives of this study were to describe the epidemiology of early onset hyponatremia, examine the investigations and interventions chosen, and assess the association of early onset hyponatremia with sodium and fluid intake in extremely preterm neonates.MethodsRetrospective study of 100 extremely preterm neonates admitted between 2018 and 2019; data was collected 1-14 days post-birth. Early onset hyponatremia was defined as: hyponatremia within first 14 days, with mild (serum Na 130-134), moderate (Na 126-129), and severe (Na ≤125 mmol/L).ResultsEarly onset hyponatremia prevalence was 85%. Amongst mild hyponatremia, 23% progressed to moderate, 21% to severe hyponatremia. Repeat Na was ordered in 84%, Na intake increased in 57%, fluid intake reduced in 7% in the 24-h following hyponatremia. Higher cumulative weight gain and fluid intake >171 ml/kg/day had higher moderate/severe hyponatremia after 7 days. Na intake higher than 5 mmol/L (OR = 1.03) and increased fluid intake (OR = 1.00) did not reduce hyponatremia risk.ConclusionsEarly onset hyponatremia is common in extremely preterm neonates. Early recognition of mild hyponatremia is critical in preventing progression to moderate-severe hyponatremia. Fluid management in the early days of life of extremely preterm neonates should prioritize weight loss and Na balance while providing adequate nutrition.