Exogenous surfactant rapidly increases PaO2 in mature rabbits with lungs that contain large amounts of saline.
Neonatal respiratory distress syndrome (RDS) is characterized by a relative surfactant deficiency and air-space edema. We tested the hypothesis that exogenous surfactant would improve gas exchange in mature surfactant-replete lungs containing large amounts of saline. Healthy young rabbits weighing 550 to 1,000 g were anesthetized and tracheotomized, and they received assisted ventilation with a FlO2 = 1. Baseline PaO2 decreased when 20 ml/kg of warmed saline (n = 6) was instilled into the lung; average PaO2 was stable and remained less than 200 mm Hg during the next 180 min. When either 50 mg/kg of natural surfactant (n = 6) or lipid-extracted surfactant (LES) (n = 6) was included in the saline solution, the PaO2 was higher (p < 0.05) than in the saline-alone group. To evaluate the effect of delayed addition of the surfactant we performed six additional experiments; the PaO2 fell to 60 +/- 6.9 SEM mm Hg after saline instillation, but within 15 min of administering LES, the PaO2 increased to 246 +/- 44.1 mm Hg, and it rose to 469 +/- 29.6 mm Hg by the end of the experiment (t = 180 min). Similar ventilator settings maintained comparable PaCO2 values in untreated and surfactant-treated groups. Gravimetric lung water contents (ml/kg body weight or ml/total lung hydroxyproline content) were markedly increased, but similar, in all groups. These studies show that the increase in PaO2 after surfactant administration to mature lungs containing large amounts of saline is similar to the increase in PaO2 seen when surfactant is given to premature infants with RDS.(ABSTRACT TRUNCATED AT 250 WORDS)
O'Brodovich
H
H
Respiratory Research Division, Hospital for Sick Children's Research Institute, Toronto, Ontario, Canada.
Hannam
V
V
D000367:Age Factors; D000818:Animals; D015633:Extravascular Lung Water / Q000502:physiology*; D006801:Humans; D007231:Infant, Newborn; D008168:Lung / Q000473:pathology; D010100:Oxygen / Q000097:blood; D011659:Pulmonary Gas Exchange; D011663:Pulmonary Surfactants / Q000008:administration & dosage / Q000502:physiology*; D011817:Rabbits; D012127:Respiratory Distress Syndrome, Newborn / Q000503:physiopathology / Q000628:therapy; D012965:Sodium Chloride / Q000008:administration & dosage; D013997:Time Factors
D011663:Pulmonary Surfactants; D012965:Sodium Chloride; D010100:Oxygen