Portal endotoxin and cytokine responses during abdominal aortic surgery

Interleukin-6 (IL-6) is a major marker of tissue injury. Surgery induces a systemic IL-6 response related to the magnitude of the operation. An exaggerated IL-6 response is associated with the development of major complications after aortic aneurysm repair. Endotoxemia is a potent stimulus for cytokine release and may occur during aortic surgery. This study attempted to examine whether the observed IL-6 response during abdominal aortic surgery is related to the development of portal endotoxemia. Serial samples of inferior mesenteric and systemic venous blood were obtained before, during, and after aortic cross-clamping in eight patients undergoing elective aortic aneurysm surgery. Portal endotoxemia was detected in only five ofthe eight patients during the surgery, and there was no correlation with the IL-6 response. Both portal and systemic IL-6 levels rose during the course of surgery, but, by the time of abdominal wound closure, the mean portal IL-6 levels were eight times higher than the systemic IL-6 levels. These results suggest that the portal circulationdraining the colon is a major source of the previously observed systemic IL-6 response to aortic surgery. The IL-6 response is not clearly related to portal endotoxemia but may reflect occult cellular injury in the colon occurring during surgery.