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

Leakage of plasma proteins into the alveolar space can inhibit pulmonary surfactant function and worsen respiratory failure in ventilated preterm infants. We tested the effect of intratracheal instillation of fetal calf serum (FCS) and fresh frozen plasma (FFP) on lung function in ventilated rats who were made surfactant-deficient by saline lavage. Post lavage, the rats were treated with air placebo, Survanta, FCS or FFP, air placebo + FCS or FFP 1 hour post lavage, or Survanta + FCS or FFP 1 hour post lavage. After 2 hours of ventilation, pressure volume curves were performed and the lungs relavaged. FCS instillation rapidly improved oxygenation when given immediately post lavage or 1 hour after placebo or Survanta instillation, whereas FFP instillation never improved oxygenation. FCS instillation increased post-treatment lavage phospholipid values, but FFP did not. Both FCS and FFP decreased lung volume, but the negative effect of FFP exceeded that of FCS. Surfactant aggregate sizing of the final lung lavages by dynamic light scattering 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 phospholipids and large surfactant aggregates, whereas FFP decreases oxygenation and surfactant aggregate size in surfactant-deficient lavaged rats.