Changes in pulmonary artery pressure in infants with respiratory distress syndrome following treatment with Exosurf.

The pulmonary artery pressure (PAP) changes were studied using Doppler echocardiography in preterm infants treated with an artificial surfactant (Exosurf) during the acute phase of respiratory distress syndrome (RDS). The ratio of pulmonary artery acceleration time to the right ventricular ejection time (AT:RVET), measured from the Doppler wave form, was determined in 38 infants before the first dose of Exosurf, at one and six hours after the first dose, immediately before the second dose of Exosurf, and at one, six, 12, 36, and 60 hours subsequently. The median AT:RVET ratio corrected for heart rate (AT:RVET(c)) increased significantly an hour after administration of the first dose of Exosurf from 0.330 (0.273-0.410) to 0.380 (0.303-0.445) and similarly an hour after the second dose from 0.426 (0.252-0.495) to 0.440 (0.373-0.500). These changes occurred against a steady increase in the median AT:RVET(c) over the first 72 hours. It is concluded that the reduction in PAP correlates well with clinical parameters of disease severity and raises questions regarding the mode of action of Exosurf.