Reperfusion lung injury after unilateral pulmonary artery occlusion

Abstract

Objective: To test the hypothesis that reperfusion of the canine lung after 1 week of vascular occlusion results in acute injury of the reperfused lung with concurrent impairment in gas exchange.

Methodology: In 11 conditioned dogs, the left pulmonary artery was completely occluded by a vascular clip placed at thoracotomy. One week later, at repeat thoracotomy, the clip was removed in six animals (reperfused group) but left in place in five (sham group). Bronchoalveolar lavage fluid (BAL) components, gas exchange, haemodynamics and histological alterations were examined.

Results: During occlusion, the mean pulmonary artery pressure and pulmonary vascular resistance increased significantly, and after 6 days there was a significant increase in ventilation to high ventilation perfusion ratio (V/Q) areas. With reperfusion, the previously occluded lung demonstrated, in comparison to the contralateral lung, a significant increase in BAL cellularity and neutrophil fraction, gross and histological evidence of oedema, and impaired surfactant activity. Shunt fraction, measured by the inert gas technique, also increased only after reperfusion, although mild hypoxaemia occurred in both groups. Endothelial abnormalities and perivascular oedema were noted in both groups, but were more marked in the reperfused lungs.

Conclusion: Reperfusion of the canine lung after 1 week of complete occlusion resulted in evidence of mild acute lung injury. The aetiology of this injury was multifactorial.