Response to bovine surfactant (surfactant TA) in two different HMD models (lambs and baboons)

The responses of Surfactant TA instillation in two groups of premature lambs (Group I, 124.8 +/- 1.1 days and Group II, 132.2 +/- 1.2 days, mean +/- SD) and one group of premature baboons (140 +/- 1.6 days) were compared to study the effectiveness of the same surfactant in different animal models. The treatment group received Surfactant TA 100 mg/kg surfactant lipid at 1 to 2 h of age. Control lambs and baboons did not receive surfactant. Sequential measurements of arterial blood gas tension, acid base status, mean airway pressure (MAP) and oxygen requirement (FiO2) were carried out for 8 h after surfactant instillation. The results show that the Group I surfactant-treated lambs improved significantly following instillation. The a/APO2 improved from 0.08 +/- 0.02 before treatment to 0.31 +/- 0.12, and the MAP decreased from 15.8 +/- 0.9 cm H2O to 13.3 +/- 1.3 cm H2O 2.5 h after treatment. At 5.5 h after treatment, the lambs given surfactant deteriorated. Group II treated lambs showed sustained improvement throughout the study period, and improvement in the treated group was not significantly different from Group II control lambs. The surfactant-treated baboons, however, showed sustained and significant improvement in a/APO2 from the time of instillation to the end of the study. These data suggest that the differences in response to the same surfactant therapy between the lamb and baboon models were due to related differences in species, lung maturation, and the differences in response to surfactant, i.e., alveolar leak of protein.