Polymer-surfactant treatment of meconium-induced acute lung injury

Substances (for example, serum proteins or meconium) that interfere with th e activity of pulmonary surfactant in vitro may also be important in the pa thogenesis or progression of acute lung injury. Addition of polymers such a s dextran or polyethylene glycol (PEG) to surfactants prevents and reverses surfactant inactivation. The purpose of this study was to find out whether surfactant/polymer mixtures are more effective for treating one form of ac ute lung injury than is surfactant alone. Acute lung injury in adult rats w as created by tracheal instillation of human meconium. Injured animals, whi ch were anesthetized, paralyzed, and ventilated with 100% oxygen and not tr eated with surfactant mixtures, remained hypoxic and required high ventilat or pressures to maintain Pa-CO2 in the normal range over the 3 h of the exp eriment. Uninjured animals maintained normal values for oxygen and complian ce of the respiratory system. The greatest improvement in both oxygenation (178%) and compliance (42%) occurred in animals with lung injury that were treated with Survanta and PEG (versus untreated control animals; p < 0.01), whereas little improvement was found after treatment with Survanta alone. Similar results were found when postmortem pulmonary pressure-volume curves and histology were examined. We conclude that adding PEG to Survanta impro ves gas exchange, pulmonary mechanics, and histologic appearance of the lun gs in a rat model of acute lung injury caused by meconium.