Double-blind, randomized, placebo-controlled Canadian multicenter trial of two doses of synthetic surfactant or air placebo in 224 infants weighing 500 to 749 grams with respiratory distress syndrome. Canadian Exosurf Neonatal Study Group.

In a multicenter, double-masked, placebo-controlled rescue trial conducted at 12 Canadian hospitals, two 5 ml/kg doses of a synthetic surfactant or air placebo were administered to 224 infants with birth weights of 500 to 749 gm who had established respiratory distress syndrome and an arterial/alveolar oxygen tension ratio of less than 0.22. The first dose was given between 2 and 24 hours of age; the second dose was given 12 hours later to the infants continuing to receive mechanical ventilation. Infants were stratified at study entry by birth weight and gender. Infants receiving synthetic surfactant showed significant improvements in alveolar-arterial oxygen tension gradient, arterial/alveolar oxygen tension ratio, and oxygen and ventilator requirements through day 7. In the group randomized to synthetic surfactant, significant improvements were seen in oxygen requirements at the first time point measured (2 hours; p = 0.02), in the alveolar-arterial oxygen tension gradient by the second time point measured (6 hours; p = 0.03), and in mean airway pressure after 6 hours. Overall mortality at 28 days was not significantly different in the two groups (50% vs 46%, air placebo group vs synthetic surfactant group; p = 0.586). Similarly, neither the incidence of bronchopulmonary dysplasia (37% vs 30%, air placebo group vs synthetic surfactant group; p = 0.089) nor the incidence of survival without BPD through 28 days (17% vs 26%, respectively; p = 0.070) was significantly different in the two groups. No significant differences in the incidence of safety-related outcomes or in adverse effects such as apnea or pulmonary hemorrhage were noted. These findings indicate that rescue therapy with synthetic surfactant results in physiologic improvements in very tiny premature infants, but improvements in overall mortality or other complications of respiratory distress syndrome were not documented in the sample evaluated.