Factors associated with surfactant treatment response in infants with severe respiratory distress syndrome.

In a prospective, randomized study of 18 infants treated with bovine surfactant (surfactant TA, Tokyo Tanabe Co, Tokyo) for severe respiratory distress syndrome, a lasting response was found in 12 infants (66%), a transient response was found in two (11%), and no response was found in four (22%) when arterial to alveolar PO2 ratios were used to define responses during the first 48 hours after treatment. In contrast, three of 23 control infants (13%) had a transient or lasting "response" to sham treatment (Pediatrics 1987;79:31-37). To determine whether maldistribution of surfactant could explain lack of response or a transient response, surfactant TA was mixed with technetium-99m sulfur colloid (approximately 300 mu Ci per infant), and eight infants with severe respiratory distress syndrome were treated six to 58 hours after birth. Scintigraphy of the lungs was performed three to 15 hours after treatment. Although a lasting response was observed in three infants, a transient one in three, and no response in two, no gross maldistribution of the radioactive label was found. Either lung received from 37% to 62% of the total radioactivity. During the past 3 years, in all infants with severe respiratory distress syndrome who were treated with surfactant (n = 29), poor or transient responses were associated with early patent ductus arteriosus and air leaks (pulmonary interstitial emphysema and pneumothoraces). Pathophysiologic conditions associated with respiratory distress syndrome are more likely to explain suboptimal responses after surfactant treatment than gross maldistribution of surfactant in the lungs.