SURFACTANT THERAPY AND HIGH-FREQUENCY JET VENTILATION IN THE MANAGEMENT OF A PIGLET MODEL OF THE MECONIUM ASPIRATION SYNDROME

In vitro data have shown a concentration-dependent inhibition of surfa ctant by meconium, while anecdotal reports demonstrate improved oxygen ation after surfactant replacement in babies with meconium aspiration syndrome, particularly in conjunction with high-frequency jet ventilat ion. We randomized 70 newborn piglets to either conventional or high-f requency jet ventilation, followed by insufflation of 3 mL/kg of a 33% meconium solution. Each group was further randomized to one of five s urfactant therapies: 1) control, 2) 4 mL/kg Survanta, 3) 8 mL/kg Surva nta, 4) 5 mL/kg Exosurf, or 5) 10 mL/kg Exosurf. We followed arterial blood gases and ventilator requirements over 6 h of ventilation. Aspir ates of airway fluids were obtained for surface tension measurements, as well as total protein and phospholipid concentrations. Using a prev iously established scoring system, a pathologist blinded to treatment evaluated four sections of lung per animal for histologic changes of m econium aspiration syndrome. There were no differences noted between g roups in any physiologic parameter measured (mean airway pressure, art erial partial pressure of oxygen/alveolar partial pressure of oxygen r atio, etc.) during the 6 h of ventilation. Airway fluid aspirate total protein concentrations increased significantly after meconium instill ation (4- to 5-fold, p < 0.007) and remained elevated in spite of surf actant therapy. There was an initial decline in airway phospholipid co ncentrations after meconium instillation followed by a rise to levels equal to or greater than premeconium levels. Surface tension measureme nts increased in all groups after meconium insufflation (p < 0.012) an d did not decline thereafter, despite standard and twice-standard surf actant doses of both types. Histology of surfactant-treated animals wa s similar to that of control piglets regardless of ventilator manageme nt. Five of 56 animals receiving surfactant had overt pulmonary hemorr hage. These data suggest that surfactant therapy with or without high- frequency jet ventilation in this animal model of meconium aspiration syndrome does not improve oxygenation, surface tension, or lung histol ogy.