Interleukin-6 production is reduced by the extraperitoneal approach in elective abdominal aortic aneurysm repair

Abstract

Abdominal aortic aneurysm (AAA) repair through a transperitoneal approach induces a systemic interleukin-6 (IL-6) response which may be related to manipulation of the bowel and mesenteric traction. This study investigates the effect of avoiding intestinal manipulation on IL-6 production by comparing the use of extraperitoneal and transperitoneal approaches in elective infrarenal AAA repair. Patients undergoing elective AAA repair were randomized into either transperitoneal (n=10) or extraperitoneal (n=8) groups. Samples of systemic and portal blood were collected intraoperatively before, during and after aortic cross clamping. In addition, systemic blood samples were obtained pre-induction, post-induction, and 6, 12, 24, and 48 hours after abdominal incision. Plasma IL-6 concentration was measured using a bioassay based on the proliferation of IL-6 dependent B9 Hybridoma cells (sensitivity of assay is 30–40 pg/ml). In the extraperitoneal group, IL-6 was not detected in either the portal or systemic circulations intraoperatively. With the transperitoneal group, IL-6 was detected in 15 of 40 (38%) portal, and 8 of 40 (20%) systemic intraoperative samples (p<0.001,x2 test). Postoperatively, IL-6 was detected in only 14 of 32 (44%) samples taken during the 48 hours after extraperitoneal repair but in 35 of 40 (88%) samples after transperitoneal repair (p<0.001,x2 test). At 6 hours, the systemic IL-6 concentration was significantly higher in the transperitoneal group (p<0.01, Mann-WhitneyU test). No correlation was seen between the plasma IL-6 concentration and aortic clamp time, duration of operation, or amount of blood lost or transfused. These results supports the suggestion that intestinal manipulation plays an important role in driving the systemic inflammatory response that may be seen after transperitoneal AAA repair.