Pulmonary injury follows systemic inflammatory reaction in infrarenal aortic surgery*

Abstract: Objective: To investigate whether an inflammatory response occurs in patients undergoing infrarenal aortic abdominal aneurysm repair, the localization and timing (ischemia and/or reperfusion) of this activation, and finally whether it affects postoperative pulmonary function. Design: Prospective, observational study. Setting. Academic referral center in Italy. Patients: We included 12 patients undergoing infrarenal aortic abdominal aneurysm repair and 12 patients undergoing major abdominal surgery. Interventions: Timed measurement of gene activation (angiotensinogen, angiotensin type I receptor, angiotensin-converting enzyme, and interleukin-6 genes) in muscle biopsies by reverse transcriptase-polymerase chain reaction (RT-PCR), and prospective assessment of interleukin-6 plasma concentration and pulmonary function (PaO2/FIO2 and PaO2/PAO(2) ratios). Measurements and Main Results. After 30 mins of aortic clamping, angiotensinogen, angiotensin type 1 receptor, angiotensin-converting enzyme, and interleukin-6 genes were all over-expressed at RT-PCR studies in quadriceps muscle of patients undergoing aortic abdominal aneurysm repair, and the overexpression persisted after reperfusion. In situ hybridization and immunohistochemistry revealed that the inflammatory response was localized in endothelial cells. A significant increase in plasma interleukin-6 concentrations was then detectable at 6 and 12 hrs after reperfusion in aortic abdominal aneurysm surgery compared with patients undergoing abdominal surgery (p < .05). The increase in interleukin-6 plasma concentration was then followed (12 and 24 hrs after surgery) by a significant reduction of PaO2/FIO2 and PaO2/PAO(2) ratios (p < .05 vs. abdominal surgery). Conclusions. The present study shows that a) during aortic surgery, the genes for interleukin-6 and for the components of the local renin-angiotensin system (angiotensinogen, angiotensin-converting enzyme, and angiotensin type I receptor subtype) are activated early in the ischemic muscle, and activation persists during reperfusion; b) interleukin-6 plasma concentration increases only in patients with tissue ischemia (aortic abdominal aneurysm), whereas no changes are detectable in patients with abdominal surgery; and finally c) the occurrence of systemic inflammatory reaction with increased interleukin-6 plasma concentrations is followed by impaired pulmonary function.