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 of the 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 circulation draining 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.