PULMONARY AND CARDIOVASCULAR EFFECTS OF A TOTALLY SYNTHETIC, PROTEINFREE SURFACTANT IN PRETERM LAMBS

Abstract

Tracheal instillation of surface active material improves lung expansion and survival. However, totally synthetic surface active materials have not been as effective as preparations derived from animal sources. We tested the effectiveness of a synthetic surfactant (DPPC, hexadecanol and tyloxapol) (EXO) in preterm lambs 131-133d gestation (term = 150d) delivered by C-section, paralyzed and mechanically-ventilated for 11 hr. 15 lambs received 5 ml/kg of EXO (75 mg lipid/kg) by tracheal instillation at delivery; 5 received 5 ml/kg of a surface active material prepared from adult sheep alveolar washes (SAM) (50 mg lipid/kg); 10 received nothing (Controls). PIP and FIO2 were adjusted to normalize PaCO2 and PaO2. The EXO group survived longer (12/15 alive at 11 hr) than the control animals (3/10 at 11 hr)(p<.05). In addition FRC, AaDO2, and PaO2 were higher and PaCO2 was lower in the EXO lambs versus the controls. There were no significant differences between the EXO and control animals in dynamic compliance, PIP, aortic or pulmonary blood pressure, cardiac output or amount of shunt through the ductus arteriosus. Although mean values for FRC, AaDO2 and PaO2 were higher in SAM-treated than in EXO-treated lambs, these differences never reached statistical significance (p>.08). Other measurements were similar in the EXO and SAM groups. EXO, a totally synthetic surfactant, produces significant improvement in survival and respiratory status in preterm lambs.