Effects of Tracheal Instillation of Natural Surfactant in Premature Lambs. I. Clinical and Autopsy Findings

Abstract

SummaryTen pairs of twin lambs 118-122 days of gestation were given either natural surfactant or diluent endotracheally before the first breath. By using the premature twin lamb model, we have been able to show that instillation of natural surfactant produced 100% survival for the duration of the study period (2 hr); stable blood gases on room air, lungs that became increasingly compliant while on the respirator, generally well aerated lungs at autopsy; good lung pressure-volume relationships; normal lung surface tension measurements; and histologic evidence of good alveolar expansion with large amounts of free intraluminal phospholipid, no epithelial damage, and no hyaline membranes. It is concluded that tracheal instillation of natural surfactant into the premature lamb protects the lungs from developing many features characteristic of the respiratory distress syndrome.Our recent studies (25) using surfactant depleted adult rat lungs suggest that nebulization of either synthetic DPL or natural surfactant is not a n effective way to restore lung pressure-volume characteristics, but that direct tracheal instillation of natural surfactant is very effective. Along these lines of investigation, Enhorning and his collaborators (18,20) have shown that tracheal deposition of surfactant into premature rabbit fetuses before the first breath enhanced air intake and improved the pressure-volume relationships of the lungs; it also increased the survival time (18). Similar results were obtained with pharyngeal deposition of surfactant before the onset of respiration in rabbits (19).The purpose of our present investigations was to determine in a more extensive way if the direct tracheal instillation of natural surfactant into a prematurely delivered lamb has a favorable effect on its clinical status and postmortem findings. The twin lamb model was chosen because of the larger size of the animals which " permits measurement of more parameters and the use of one as a Speculation control and the other as the experimental lamb, thus reducing the ~h~ success of these esperiments is possibly due to the use of problems associated with variations in gestational age, nutritional ..,,hole" rather than some of its state, size, and other factors. Moreover, it appeared to us that if ~h~ precise biochemistry and physical ,.hemistry of the results were favorable in lambs weighing 1-2 kg, a more direct surfactant is very controversial, and for therapeutic purposes, it be made lhe lreatment Or prevention RDS might be best for the moment to concentrate on the natural in human premature babies. biologic product. MATERIALS AND METHODSIt has been demonstrated that the lungs of infants dying of PROTOCOL FOR ANIMALS respiratory distress syndrome (RDS) possess abnormal surface properties (5) and low levels of phospholipids (2.9. 10). It has also Ten pregnant ewes between 1 18 and 122 days of gestation been shown that the quantity and quality of surface-active phos-known by x-ray examination to possess twin fetuses were used. pholipids (surfactant) ...

Cardiovascular Effects of Surfactant Suspensions Given by Tracheal Instillation to Premature Lambs

“…In previously reported protocols using surfactant suspensions in prematurely delivered lambs, animals at 120-130 days gestational age have been used (1,10,12). These lambs had a degree of pulmonary immaturity more severe than most infants with RDS.…”

“…Instillation of surfactant suspensions to premature lambs did not adversely affect cardiovascular status; however, some lambs did have a transient deterioration of lung function after surfactant instillation. Abbreviations RDS, respiratory distress syndrome Fr.. French Suspensions of surfactant given via the trachea either at birth or after the onset of respiratory failure dramatically improve lung function in premature monkeys (5), rabbits (6), and lambs (1). This encouraging experience has resulted in two clinical trials of the administration of surfactant suspensions as therapy for infants with RDS (7,17).…”

Surfactants: past, present and future

“…After 5 years Forrest Adams and his colleagues in California demonstrated the beneficial effects of a natural bovine surfactant on the lungs of preterm lambs. 13 One of his co-authors was Tetsuro Fujiwara from Japan who was then working in Adams' laboratory in California.…”

The Contractility and Performance of the Preterm Left Ventricle before and after Early Patent Ductus Arteriosus Occlusion in Surfactant- Treated Lambs

“…Recent advances using assisted ventilation and surfactant therapy have made it possible to study early postnatal cardiovascular adaptation in premature animals under acceptable physiological conditions (6,7). Early cardiovascular adjustments to left-right ductal shunting have been infrequently studied under such circumstances (8,9).…”