Elevated atrial natriuretic factor in neonates with respiratory distress syndrome.

Atrial natriuretic factor (ANF) plasma concentrations were measured in 16 healthy term newborn infants and in 18 preterm infants with respiratory distress syndrome during the first 4 postnatal days. Changes in the plasma concentration of ANF were then correlated with postnatal age, severity of respiratory distress, and water and sodium balance. The plasma ANF concentration in healthy term infants increased during the first 2 days of life. Similar values were observed among preterm infants requiring hood oxygen. The plasma ANF concentrations were substantially higher in preterm infants receiving positive pressure ventilation. All infants had negative water and sodium balance during the period of study. No correlation was found, however, between absolute plasma ANF concentrations and urinary flow rate, sodium excretion, or fractional sodium excretion, suggesting that ANF did not exert a dominant role in the excretion of sodium in these infants.