Role of the neutrophil in the development of systemic inflammatory response syndrome and sepsis following abdominal aortic surgery

Introduction: There is evidence to suggest that the polymorphonuclear neutr ophil (PMN) plays a critical early step in the development of the ischaemia -reperfusion syndrome, the systemic inflammatory response syndrome (SIRS) a nd sepsis. The PMN receptor CD16 plays an important role in phagocytosis, c ell-mediated cytotoxicity and the release of free radicals and proteolytic enzymes. The aim of this study was to determine whether there is any relati onship between PMN CD16 expression, phagocytosis and the development of sep sis. Methods: Fifty patients who underwent elective infrarenal abdominal aortic aneurysm repair were studied. Venous blood was taken before operation, thro ughout surgery and for 7 days after operation. CD16 expression was measured , unstimulated and following further stimulation, by means of flow cytometr y. Phagocytosis was determined using flow cytometry. Results: Some 36 patients had an uncomplicated recovery; 14 developed SIRS or sepsis. There was no difference between the two groups with respect to n utritional, co-morbid or technical factors. In the group that developed sep tic complications after operation, the level of PMN CD16 expression was sig nificantly higher before surgery (mean channel fluorescence (MCF) 30.2 vers us 10.4; P < 0.05, Mann-Whitney U test) and throughout the postoperative pe riod. Surgery produced no change in CD16 expression. After operation, stimu lation of PMNs in the septic group resulted in a fall in CD16 expression (4 0.8 versus 20.4 MCF; P < 0.05, Mann-Whitney U test); surgery produced no ch ange in the level of expression in the uncomplicated group. Conclusion: This study provides evidence of phenotypic and functional diffe rences in neutrophil behaviour in patients who develop sepsis following ane ursym surgery.