Surfactant levels after reversible tracheal occlusion and prenatal steroids in experimental diaphragmatic hernia

Background/Purpose: In normal lungs, fetal tracheal occlusion (TO) induces lung growth but decreases the number of type II cells; this is remedied if TO is released (TR) before delivery. In the current study, the effects of T O with or without TR on pulmonary structure and surfactant were assessed in the ovine model in which lung hypoplasia was induced by creation of a diap hragmatic hernia (CDH). Methods: A left-sided CDH was created in fetal lambs at 80 days gestation; TO was done at 108 days; and TR at 129 days. All ewes were given 1 dose of glucocorticoids at 135 days. At 136 days, the fetus was delivered. Lung wei ght to body weight ratio, mean terminal bronchiole density, type II cell de nsity, bronchoalveolar ravage fluid (BAL) phosphatidylcholine (PC), BAL sur factant protein A (SP-A) and B (SP-B), and lung tissue SP-A and SP-B were a ssessed in CDH, CDH with TO, CDH with TO and TR. and controls. Results: CDH lungs were hypoplastic and structurally immature, but had incr eased type II cell density. TO with or without TR caused lung growth with n ormalization of lung parenchymal architecture and type II cell density. Alt hough the BAL SP-A and BAL SP-B were similar in all 4 groups, the BAL PC wa s low in CDH with or without TO or TR. Also, lung tissue SP-B levels were l ow in CDH with or without TO or TR. However, lung tissue SP-A levels were n ormal in CDH, but low in CDH with TO with or without TR. Conclusions: Despite the finding that lung morphology was improved in CDH w ith TO with or without TR animals, surfactant content and composition remai ned abnormal. Although surfactant secreted early by the fetus into alveolar spaces contained normal levels of BAL SP-A and BAL SP-B, the low levels of BAL PC and low lung tissue stores of SP-B indicate that these experimental lambs may experience respiratory insufficiency soon after birth. This impl ies that prophylactic surfactant at birth might be beneficial for CDH. J Pe diatr Surg 36:122-127 Copyright (C) 2001 by W.B. Saunders Company.