Surfactant replacement therapy in preterm neonates: a comparison of postmortem pulmonary histology in treated and untreated infants.
New histological lesions have been reported in the lungs of preterm neonates treated with surfactant for respiratory distress syndrome (RDS). Globular deposits of hyaline maternal in parenchymal air spaces, absence of hyaline membranes, and increased interstitial cellularity and edema without associated fibrosis have been described. Fifteen histological findings were assessed in the lung pathology of 76 infants with RDS from three study groups. Group I (24 infants) died in the presurfactant era (before 1982), group II (26 infants) died despite having surfactant treatment, and group III (26 infants) were either untreated controls or did not receive surfactant for other reasons. The three groups were comparable in respect of sex and survival time. All infants were 34 weeks of gestation or less. Infants with a significant congenital abnormality or pulmonary hypoplasia were excluded. The 76 cases were assessed independently and "blindly" by two pathologists. The histological findings assessed were alveolar collapse; epithelial necrosis, proliferation, and metaplasia; hyaline membranes; dilated lymphatics; pulmonary interstitial emphysema; interstitial edema, inflammation, and fibrosis; arteriolar muscular hyperplasia; interstitial and intra alveolar hemorrhage; massive pulmonary hemorrhage; and pneumonia. No significant differences were found in any of the histological findings between the three groups. The hyaline membranes seen in the surfactant-treated infants were identical to those in the untreated lungs and were of the characteristic linear type. Interstitial fibrosis, inflammation, and edema were present in all three groups. It has also been suggested that surfactant therapy protects preterm infants from interstitial hemorrhage but predisposes them to intra-alveolar hemorrhage. No significant difference in the incidence of intra-alveolar and interstitial hemorrhage in the three groups was identified.