FOCAL AORTIC INJURY CAUSED BY CANNULATION: INCREASED PLASMA PROTEIN ACCUMULATION AND THROMBOSIS

Previous studies have shown evidence of “spontaneous” injury associated with increased permeability in focal areas of non-atherosclerotic animal aortas. In this study, a mild intimal injury was induced by brief cannulation of the thoracic aorta of rabbits and pigs to examine whether focal aortic plasma accumulation is due to the injury per se or to other effects. Evans blue, a marker of plasma albumin, was used to visualize plasma accumulation. The animals were killed 10 minutes to 5 hours after cannulation. In all animals, blue-stained, sharply demarcated streaks were found in the thoracic aorta. By microscopy, the streaks showed loss of endothelium and, frequently, platelet thrombi with or without fibrin, leucocytes, or red blood cells. The basal platelets were in contact with exposed basement membrane, or with fibres of elastin or collagen. The inner layers of the aortic wall corresponding to the streaks showed signs of oedema. In contrast, unstained areas of the aorta had an intact endothelium, and neither thrombosis nor oedema was present. The observations show that a mild and brief injury of the aortic intima can cause both mural thrombosis and leakage of plasma into the inner layers of the aortic wall. The extent of the leakage appeared to be independent of haemodynamic effects. The injury was similar to, but more severe, than most “spontaneous” lesions.