Acute effects of synthetic surfactant replacement on pulmonary blood flow in neonatal respiratory distress syndrome.

To assess the acute effects of surfactant replacement therapy on the pulmonary blood flow in neonatal respiratory distress syndrome (RDS), 23 distressed infants were studied before and for 1 hour after either synthetic surfactant instillation (n = 13) or endotracheal suctioning (n = 10). Doppler ultrasound was used to measure blood flow velocity and flow velocity integral, representing volumetric flow, of the left pulmonary artery branch, ductal left-to-right shunt, and ascending aorta. Surfactant instillation increased the left pulmonary artery and ductal shunt flow velocity and flow velocity integral for 1 hour in 10 of 13 treated infants, whereas no change was found after endotracheal suctioning. There was a significant (P < 0.05) correlation between the changes in the pulmonary artery and ductal flow values at 1 hour after surfactant treatment. The mean increase during 1 hour after treatment in the pulmonary artery flow ranged from 15 to 25% and in the ductal left-to-right shunt from 28 to 33%. No change in the aortic flow or heart rate was found in either group. Our results thus suggest that synthetic surfactant therapy may acutely increase pulmonary blood flow and ductal left-to-right shunting in infants with RDS.