The effect of early treatment of
patent ductus arteriosus (PDA) on the acute course of
hyaline membrane disease was tested in a primate model, after intratracheal administration of 100 mg/kg exogenous bovine
surfactant phospholipids at mean ages between 2.3-2.4 h. Twenty-two premature baboons were divided into four groups: seven animals were controls (group A); five were treated with
surfactant but PDA was not intervened (group B); in five
surfactant treatment was followed by three doses of 0.2 mg/kg intravenous
indomethacin beginning at a mean age of 5.5 h (group C); and in five
surfactant treatment was followed by a surgical
ligation of PDA between 5-5.5 h of age. After
surfactant instillation in groups B, C, and D, a prompt and sustained improvement was noted in a/APO2, mean airway pressure,
ventilator efficiency index and pulmonary compliance. However, no consistent differences were found in the respiratory variables within the
surfactant treated groups during the 72-h experiment: the respiratory course in the animals treated for PDA (groups C and D) was generally similar to the animals in which PDA was not treated (group B). In animals treated with
surfactant and
indomethacin (group C) the mean aortic blood pressure was maintained more optimally as compared to the other three groups. These findings suggest that although a significant early ductal shunting does occur after exogenous
surfactant therapy in this animal model, the expected pulmonary deterioration does not occur, and an early abrupt interruption of PDA does not seem to provide additional advantage to the immediate course of
hyaline membrane disease.