Effects of C1 inhibitor and r-SP-C surfactant on oxygenation and histologyin rats with lavage-induced acute lung injury

Objective: To assess the effects of C1 inhibitor (INH) administration and r -SP-C surfactant application on oxygenation and lung histology in an acute respiratory distress syndrome model. Design and setting: Randomized, controlled experimental study in an animal research laboratory. Material: 36 adult male Sprague-Dawley rats. Interventions: Animals were subjected to repetitive lung lavage. Four exper imental groups and two control groups were studied: groups 1 and 2 served a s controls. Animals of groups 3-6 received 200 U/kg body weight C1-INH (gro up 3), 25 mg/kg r-SP-C surfactant (group 4) or both (group 5) at 60 min pos tlavage (pl). Animals of group 6 were treated with 200 U/kg C1-INH1 at 10 m in pl. Animals of group 1 were killed 60 min (min) pl, animals of groups 2- 6 were killed at 210 min pl. Thereafter the lungs were excised for histolog ical examination. Measurements and results: Hyaline membrane formation, intra-alveolar neutro phil (PMN) accumulation and intra-alveolar/perivascular haemorrhage were gr aded semiquantitatively (0-4). Blood gases were determined 120, 150, 180 an d 210 min pl. At 210 min Pl PO2 in group 4 (456 +/- 74 mmHg) and group 5 (3 87 +/- 155 mmHg) was significantly higher than in controls (72 +/- 29 mmHg) or after C1-INH monotherapy (group 3: 120 +/- 103, group 6: 63 +/- 12 mmHg ). PMN infiltration after C1-INH monotherapy was significantly less severe than in controls. The combination of rSP-C surfactant and C1-INH led to sig nificantly lower PMN infiltration than surfactant monotherapy. Conclusion: In this lavage-induced acute respiratory distress syndrome mode l the administration of C1-INH might be followed by a higher clinical effic acy of exogenously supplied recombinant SP-C surfactant.