Evaluation of the Sodium Serum Level in Infants with Jaundice

Inadequate milk intake during the first year of neonate’s life can result in weight loss, severe hyperbilirubinemia, and sometimes hypernatremia. We aimed to determine the relationship between neonatal weight loss and hypernatremia in term breastfed infants with idiopathic jaundice, as well as the necessity of sodium concentration measurement in newborns with idiopathic jaundice via weight loss measurement. In this cross-sectional study, we examined 273 infants with jaundice of unknown etiology at Ghaem Hospital, Mashhad- Iran, in 2008 to 2012. The study sample consisted of 226 infants in the control group (serum sodium concentration <150 mg/dl) and 47 infants in the case group (serum sodium concentration ≥150 mg/dl). The subjects were evaluated in terms of weight change and neonatal risk factors. Finally, we assessed the sensitivity, specificity, and positive and negative predictive values of weight loss in the measurement of serum sodium concentration. The mean sodium concentration was 155.8±5.51 mg/dl in the case group, and 139.4±4.09 mg/dl in the control group. There was a significant relationship between weight loss and hypernatremia (P<0.001). With 70% sensitivity and 83.6% specificity, the positive predictive value of ≥ 1.5% daily weight loss was 50% for hypernatremia, in infants younger than 10 days of age; the negative predictive value was 92% (P≤0.001). According to the results, the measurement of sodium concentration is not required in the first ten days of neonate’s life if total weight loss is less than 7% or daily weight loss is less than 1.5%.