1379 SURFACTANT REPLACEMENT AND PATENCY OF THE DUCTUS ARTERIOSUS (DA) IN LAMBS

Abstract

Extracted calf lung lipids (CLL) instilled into 127-129 day gestation lambs at birth prevents respiratory failure; we sought to determine the early status of the DA in such animals. Lambs were delivered by hysterotomy, tracheotomized, and catheters placed in the main pulmonary artery (PA) 1 cm beyond the valve under fluroscopy, the ascending aorta and descending aorta. CLL was instilled in 6 lambs, saline in 5, mechanical ventilation was started and umbilical cord severed. Blood gases and aortic PGE2 levels were obtained hourly. DA status was determined by the PA to aorta pressure gradient, aorta-PA xoygen difference, and microsphere trapping in the lung after left ventricular injection. Only 1 of the 5 control animals survived to 6 hours, 4 showed some transient constriction of the DA, and one of the 4 functional closure for 2 hours. In the treated animals, all showed constriction of the DA, 3 were functionally closed for 6 hours, 2 were constricted, 1 had re-opened. DA status was not correlated with aortic PGE2 levels, which declined during the experiment in all animals, nor with PaO2. Prevention of respiratory failure by CLL instillation at birth is associated with constriction of the DA in the first 6 hours.