ADDITION OF SYNTHETIC SURFACTANT PROTEIN B TO SURVANTA IMPROVES GAS EXCHANGE IN SURFACTANT-DEFICIENT RATS. † 2114

Abstract

Surfactant protein B (SP-B) is critical to surfactant function. Survanta®, a modified bovine lung extract, contains less SP-B than surfactants derived from lung lavage (Seeger et al., Eur Resp J 1993;6:971). Supplementation of Survanta with native SP-B increases dynamic compliance and deflation lung volume in preterm rabbits (Mizuno et al., Pediatr Res 1995;37:271). We hypothesized that the in vivo function of Survanta can be improved by supplementation with synthetic SP-B and SP-C and tested this hypothesis in a surfactant-deficient rat model. Full length SP-B1-78 and palmitoylated SP-C1-34 were synthesized, purified, derivatized, and analyzed by mass spectrometry and amino acid analysis. Survanta was extracted, unmodified (Surv-1) or enriched with 1% SP-B (Surv-2), 2% SP-B (Surv-3), or 2% SP-B + 1% SP-C (Surv-4), and resuspended. In vitro surface activity was tested on a modified Langmuir/Wilhelmy balance and SP-B and SP-C content were measured by Fourier transform infrared spectroscopy. Adult rats were anesthetized, tracheotomized, had an arterial line placed, and were ventilated with 100% oxygen, a peak inspiratory pressure of 30 cm H2O and a rate of 40/min. The lungs were lavaged with warmed normal saline until the PaO2 dropped below 60 torr, at which time 100 mg/kg of one of the four surfactant preparations was instilled. After 15 min of ventilation, the rats were killed and pressure-volume curves performedin situ. The mean arterial/Alveolar PO2 ratio was 0.08 post-lavage and increased by 74% after treatment with Surv-1 (n=5), by 92% after treatment with Surv-2 (n=6), by 257% after treatment with Surv-3 (n=5), and by 202% after treatment with Surv-4 (n=6). Surv-4 not only improved PaO2, but also reduced PaCO2 values. These data suggest that the addition of 2% synthetic SP-B to Survanta improves its short-term positive effects on oxygenation in this surfactant-deficient rat model.