Ischemic Intestinal Injury during Cardiopulmonary Bypass Does Not Show an Association with Neutrophil Activation

Abstract

Background: Neutrophil activation and tissue sequestration are crucial events in intestinal ischemia-reperfusion injury, but their role in the gut wall after clinical cardiopulmonary bypass (CPB) remains unclear. We tested whether local post-CPB inflammatory response in the gut wall would be associated with intestinal mucosal perfusion. Methods: Twenty pigs underwent 60 min of aortic clamping and 75 min of normothermic perfusion. Intestinal biopsies were taken after 120 min of reperfusion. Based on ileal myeloperoxidase activity (MPO), the animals were divided into 2 groups, CPB-induced increase in MPO (MPO+) versus no such increase (MPO–), for comparison of the parameters that measure gut mucosal perfusion. Ileal p_CO_₂ and intramucosal pH were determined, and arterial gases were analyzed. Additionally, several hemodynamic parameters and blood thrombin-antithrombin complexes (TAT) were measured. Results: Myocyte degeneration, endothelial activation and vasculitis were more pronounced in the MPO+ group (p < 0.05), while the MPO– group showed significantly increased pi_CO_₂ and lower mucosal pH values during reperfusion. Hemodynamics and TAT levels did not differ between the groups. Conclusion: Tissue sequestration of neutrophils was poorly associated with perturbed mucosal perfusion after CPB. Mechanisms of gut wall injury after a low-flow/reperfusion setting can differ from those in reperfusion injury after total ischemia.