Role of the neutrophil in the development of sepsis following abdominal aortic aneurysm surgery

Abstract Background: There is evidence to suggest that the neutrophil (PMN) plays a critical early step in development of the ischaemia–reperfusion syndrome and sepsis. Not all patients undergoing aortic aneurysm repair develop these postoperative complications. The PMN receptor CD16 plays an important role in phagocytosis, cell‐mediated cytotoxicity and the release of free radicals and proteolytic enzymes. This study determined if there is any relationship between PMN CD16 expression, phagocytosis and the development of sepsis. Methods: Some 50 patients (39 men and 11 women, median age 70 years) who underwent elective infrarenal abdominal aortic aneurysm repair were studied. Venous blood was taken before operation, throughout surgery and for 7 days afterwards. CD16 was measured, unstimulated and following further stimulation with phorbol myrisate, lipopolysaccharide and N ‐formyl‐methionyl‐leucyl‐phenylalanine using flow cytometry. Phagocytosis was measured using flow cytometry and the production of elastase using an enzyme‐linked immunosorbent assay. Sepsis was defined according to the ACCP/SCCM definition. Results: There were 36 uncomplicated operations and 14 patients with sepsis. There was no difference between the two groups in respect of nutritional, co‐morbid or technical factors. In the group that developed septic complications, the level of PMN CD16 expression was significantly higher before operation (30·2 versus 10·4 mcf; P < 0·05, Mann–Whitney U test) and throughout the postoperative period. Surgery produced no change in CD16 expression in either the septic or uncomplicated group. Stimulation of the PMNs before operation caused an increase in CD16 expression in both groups. After operation, stimulation of PMNs in the septic group resulted in a fall in CD16 expression (40·8 versus 20·4 mcf; P < 0·05, Mann–Whitney U test); surgery produced no change in the level of expression in the uncomplicated group. Phagocytic ability was comparable before operation (91·2 versus 94·2 mcf), but showed a greater reduction in the septic group after operation (73·4 versus 86·2 mcf; P < 0·05, Mann–Whitney U test). Elastase concentration was also similar before operation (48 versus 49 μg l −1 ); after operation, there was a greater increase in the septic group (166 versus 104 μg l −1 ; P < 0·05, Mann–Whitney U test). Conclusion: This study provides evidence of functional differences in PMN behaviour in patients who subsequently develop sepsis following aneurysm surgery. This difference occurs early in the postoperative course and it may be possible to identify these patients before operation. © 2000 British Journal of Surgery Society Ltd