Differential expression of neutrophil adhesion molecules during coronary artery surgery with cardiopulmonary bypass

Background: Activation of neutrophil adhesion molecules and subsequent neut rophil adhesion to vascular endothelium are key events initiating inflammat ory organ dysfunction after cardiopulmonary bypass and ischemic reperfusion , Objectives: We sought to characterize neutrophil integrin CD11b and L-sel ectin activation associated with coronary artery bypass graft surgery and t o determine whether neutrophil activation contributes to their sequestratio n on postbypass reperfusion, Methods: Twenty patients undergoing routine co ronary artery bypass were studied, Heparinized whole blood was simultaneous ly sampled from a central venous line, aorta, coronary sinus, and right and left atrium before, during, and up to 20 minutes after cardiopulmonary byp ass, Neutrophil counts were obtained, and neutrophil CD11b and L-selectin e xpression was determined by flow cytometric analysis in whole blood. Result s: CD11b expression on circulating neutrophils increased during cardiopulmo nary by-pass, peaking at 145% of baseline level after release of the aortic clamp and then declined by 20 minutes after bypass (analysis of variance, P = .003). No change in neutrophil L-selectin expression was observed durin g cardiopulmonary bypass. Neutrophils responded to ex vivo stimulation by C 5a and leukotriene B-4 during cardiopulmonary bypass but not at 24 hours af ter the operation. After reperfusion, neutrophil loss, but not local activa tion, was demonstrated in the coronary and pulmonary circulations. Conclusi ons: Upregulated CD11b expression on neutrophils is likely to contribute to neutrophil sequestration in the heart and lungs after bypass, but neutroph il activation map be Limited by their reduced responsiveness to agonist sti mulation, CD11b represents a potential therapeutic target for diminishing i nflammation after cardiac operations.