Pulmonary pathology in surfactant-treated preterm infants with respiratory distress syndrome: an autopsy study

The present study examines the histological features of the lungs of neonates who died of respiratory distress syndrome or related complications after surfactant therapy. Our aim was to determine whether these lungs showed any unusual histological findings. Complete autopsies were performed 6-12 h after death in 10 surfactant-treated preterm infants and in 30 infants who died before surfactant therapy was available. Representative paraffin sections of all pulmonary lobes, stained with haematoxylin and eosin, were examined microscopically. A few selected slides were also stained with periodic acid-Schiff, Vierhoff-van Gieson, and Mallory trichrome. Hyaline membrane disease and bronchopulmonary dysplasia were present in each group, although there was an increased incidence of intra-alveolar haemorrhage in surfactant-treated babies (in 8 of 10 surfactant-treated as compared with 7 of 30 untreated babies). Amongst those treated with surfactant, we observed the persistence of acute alveolar damage with unresolved hyaline membrane disease in 5 infants who died at the ages of 5, 6, 10, 12, and 13 days, respectively, and histological evidence of pneumocyte type 2 hyperplasia and dysplasia in 2 infants who died at 22 and 41 days of age, respectively. These observations reveal that surfactant-treated infants who fail to respond to therapy have continuing alveolar injury and an increased incidence of intra-alveolar haemorrhage. Since oxygen radicals can induce pneumocyte damage and necrosis and since free radicals provoke alveolar haemorrhage in animal models, we propose that the lesions we observed may stem from a lack, in some preterm babies, of specific mechanisms that detoxify oxygen radicals.