PULMONARY CLEARANCE OF TC-99M-DTPA IN EXPERIMENTAL SURFACTANT DYSFUNCTION TREATED WITH SURFACTANT INSTILLATION

Background: Breakdown of the alveole-capillary barrier is a characteri stic feature of respiratory distress syndrome. Restoration of alveole- capillary barrier function may be an important aspect of surfactant ra placement therapy. We examined the effect of surfactant instillation o n alveole-capillary barrier function in an experimental model of surfa ctant dysfunction by measuring pulmonary clearance of Tc-99m-DTPA. Met hods: Nineteen rabbits were tracheotomized and mechanically ventilated . Surfactant dysfunction was induced by administration of a synthetic detergent in aerosol form. Detergent was given to 13 rabbits; seven ra bbits were then treated with instillation of natural surfactant, where as six rabbits received saline. Six rabbits were used as untreated con trols. An aerosol of Tc-99m-DTPA was administered to all animals and t he pulmonary clearance was measured with a gamma camera. Results: Tc-9 9m-DTPA cleared from the lungs with a half-life of 71+/-22 min in the control animals, 21.4+/-7.4 min in the surfactant-treated animals and 5.8+/-1.5 min in the saline-treated animals. The difference in half-li fe between groups was highly significant (P<0.001). There was no chang e in arterial oxygenation or compliance in controls or in animals trea ted with saline. In animals treated with surfactant, a small transient reduction in arterial oxygen tension and a more long-standing reducti on in compliance were observed. Conclusion: Surfactant treatment thus significantly attenuated the effect of detergent treatment but did not restore alveole-capillary transfer of Tc-99m-DTPA to normal. (C) Acta Anaesthesiologica Scandinavica 41 (1997).