A Pilot Study For The Mechanisms Of Systemic Inflammatory Reaction Follows Infrarenal Aortic Surgery

[Objective] To investigate whether the activation of the components of local renin-angiotension system including angiotension (AGTN), angiotension-converting enzyme (ACE), and angiontension type 1 receptor subtype (AT1) together with inflammatory cytokin interleukin-6 (IL-6) occurs in patients undergoing infrarenal aortic abdominal aneurysm (AAA) repair, and whether these activation will affect the level of IL-6 concentration in systemic circulation.[Design] Prospective, observational study.[Setting] Clinical center in a teaching hospital.[Patients] Ten patients undergoing infrarenal aortic abdominal aneurysm repair and another 10 patients undergoing major abdominal surgery.[Interventions] The gene activation (AGTN, AT1, ACE, and IL-6 genes) in muscle biopsies were measured by real time reverse transcription polymerase chain reaction (real time PCR) and immunohistochemistry, comparing the differences in gene activation between the lower and upper limb muscle biopsies as well as in lower limb muscle biopsies between AAA and non-AAA patients. Blood samples were collected from upper limb vein after operation to measure interleukin-6 plasma concentration.[Results] After aortic clamping, AGTN, ATI, ACE, and IL-6 genes were all over-expressed at real time PCR studies in quadriceps muscle of patients undergoing aortic abdominal aneurysm repair, and the overexpression persisted after reperfusion. Immunohistochemistry revealed that the inflammatory response represented by IL-6 expression in muscle biopsies were localized in endothelial cells. A significant increase in plasma interleukin-6 concentrations was then detectable at 6, 12, 24 and 36 hrs after reperfusion in aortic abdominal aneurysm surgery compared with patients undergoing abdominal surgery (P < 0.01). The consistent real time PCR results were not founded in upper limb biopsies in AAA patients and in non-AAA patients. Similarly, in non-AAA patients, there was no plasma IL-6 concentration change after operation.[Conclusions] The present study showed that: a) the genes of interleukin-6 and the components of the local RAS were activated early in the ischemic muscle during aortic surgery, and activation persisted during reperfusion;b) interleukin-6 plasma concentration increased only in patients with tissue ischemia (aortic abdominal aneurysm), whereas no changes was detectable in patients with abdominal surgery. It could be inferred that it was the lower limb muscle that initiated the systemic inflammatory reaction after aortic surgery.