Paradoxical effects of exogenous proteins on lung function in surfactant-deficient rats

Leakage of plasma proteins into the alveolar space can inhibit pulmonary su rfactant function and worsen respiratory failure in ventilated preterm infa nts. We tested the effect of intratracheal instillation of fetal calf serum (FCS) and fresh frozen plasma (FFP) on lung function in ventilated rats wh o were made surfactant-deficient by saline lavage. Post lavage, the rats me re treated with air placebo, Survanta, FCS or FFP, air placebo + FCS or FFP I hour post lavage, or Survanta + FCS or FFP I hour Post lavage. After 2 h ours of ventilation, pressure volume curves were performed and the lungs re lavaged. FCS instillation rapidly improved oxygenation when given immediate ly Post lavage or I hour after placebo or Survanta instillation, whereas FF P instillation never improved oxygenation. FCS instillation increased post- treatment lavage phospholipid values, but FFP did not. Both FCS and FFP dec reased lung volume, but the negative effect of FFP exceeded that of FCS. Su rfactant aggregate siting of the final lung lavages by dynamic light scatte ring showed a definite shift towards smaller aggregates after FFP, but not after FCS, instillation. These data suggest that intratracheal instillation of FCS improves oxygenation and preserves the alveolar presence of phospho lipids and large surfactant aggregates, whereas FFP decreases oxygenation a nd surfactant aggregate size in surfactant-deficient lavaged rats.