SURFACTANT RESCUE IN THE FETAL LAMB MODEL OF CONGENITAL DIAPHRAGMATIC-HERNIA

Surfactant therapy given before the onset of ventilation (surfactant p rophylaxis) has been shown to improve oxygenation, ventilation, and pu lmonary hemodynamics in the lamb model of congenital diaphragmatic her nia (CDH). The aim of this study was to assess the efficacy of surfact ant administered after the onset of ventilation (''surfactant rescue'' ). Ten lambs with surgically created CDH were instrumented, at full te rm, to measure pulmonary blood flow and pulmonary vascular resistance (PVR). Catheters also were positioned for monitoring of systemic blood pressure and arterial blood gases. The animals were delivered and pre ssure-ventilated according to a standard protocol (PIP, 30 cm; PEEP, 4 cm; respiratory rate, 60 breaths per minute). After 30 minutes of ven tilation, five animals received an intratracheal dose of calf lung sur factant extract (50 mg/kg). The animals were studied for 4 hours. Surf actant rescue had no discernible effect on P-CO2, P-CO2, or pH. There was an increase in pulmonary blood flow, but it was not significant. T he dramatic improvement in oxygenation, ventilation, and pulmonary blo od flow found with prophylactic surfactant cannot be reproduced when s urfactant is administered as rescue therapy. This indicates that the s urfactant is not being delivered adequately, the lungs have already in curred significant barotrauma, and/or the surfactant is being inactiva ted by alveolar protein. Therefore, the authors suggest that when exog enous surfactant therapy is being considered for the fetus or newborn with CDH, it should be administered as early as possible, preferably b efore the infant's first breath. Prenatal diagnosis and delivery in a tertiary care center would facilitate this optimum management. Copyrig ht (C) 1996 by W.B. Saunders Company.