Immunological and physiological responses to aortic surgery: Effect of reperfusion on neutrophil and monocyte activation and pulmonary function

Background. The aims of this study were to evaluate the effects of aortic clamping and unclamping on neutrophil and monocyte activation and release of plasma mediators in 20 patients undergoing elective aortic aneurysm surgery, and to correlate these findings with pulmonary haemodynamics and gas exchange. Methods. Simultaneous arterial and mixed venous samples were obtained during and after aortic clamping and unclamping. Results. Neutrophil respiratory burst activity in mixed venous samples increased significantly during the period of aortic clamping. An initial increase in neutrophil CD11b expression in venous blood 5 min after clamp removal was followed by a significant decrease in level of expression. Plasma tumour necrosis factor levels increased at the end of the cross-clamp period and reached a maximum 60 min following reperfusion. There was a significant and sustained rise in plasma thromboxane B₂ levels following clamp removal. This increase correlated with the development of increased pulmonary vascular resistance. Conclusion. This study confirms the central role played by activated neutrophils in the early stages of reperfusion injury and also suggests a role for plasma mediators in mediating cardiopulmonary dysfunction during major vascular surgery.