Experimental post-traumatic lung insufficiency in dogs: ultrastructure of lung lesions.

The ultrastructure of developing lung lesions in two groups of dogs exposed to a combination of haemorrhagic hypotension and liver trauma was studied with particular attention to changes at the alveolar level and lung micro-vessels. Lung samples were obtained every four hours and at collapse in one group and 12 hrs after initiation of the trauma in the other. An interstitial oedema was recognized in biopsies obtained 4 hrs after initiation of the trauma, and before marked lesions were observed at the ultrastructural level in endothelial cells. Endothelial damage was, however, evident in biopsies obtained at 8 hrs and at collapse. Aggregates of degranulated and degenerated leucocytes and platelets were occasionally found to obstruct respiratory capillaries together with erythrocytes, some of which seemed to be haemolysing. A considerable amount of protein-rich oedema, cellular debris and fibrinoid material was found in alveolar lumina at collapse. The present experiments indicate that increased vascular permeability in lung micro-vessels is of importance for the development of the characteristic lesions seen in shock lung. Possible pathogenetic mechanisms, initiating the lung lesions, are discussed with special emphasis on the significance of kinin activation and the presence of polymorphonuclear leucocytes and microthrombi.