Higher IL-6 levels but not IL6 −174G > C or −572G > C genotype are associated with post-operative complication following coronary artery bypass graft (CABG) surgery

Caucasian patients undergoing first-time elective CABG were studied. IL-6 levels were measured pre-, 6 h and 24 h following surgery and genotypes for IL6 gene variants −174G > C and −572G > C were obtained. Clinical data was collected daily until patient discharge. Patient outcome was categorised as with (ICUC, n = 177) and without (NICUC, n = 189) a post-operative complication during the ICU period and with (POC, n = 215) and without (NC, n = 151) a post-operative complication during hospitalisation. IL-6 levels pre- and at 24 h were greater in POC and ICUC than NC and NICUC, respectively. Pre- IL-6 levels independently predicted (for 1 standard deviation increase in log IL-6) POC (OR 1.4, 95% CI 1.1-1.7, p = 0.008) and ICUC (OR 1.3, 95% CI 1.0-1.6, p = 0.02) outcomes. Overall, the IL6-572G > C had an effect over time on IL-6 levels (p = 0.04) and on IL-6 levels in NC (P = 0.008) and NICUC (p = 0.006). However, no associations were found with the IL6 −572G > C or −174G > C variants on IL-6 levels at individual time-points or by outcome group. Thus, in conclusion, elevated pre-operative IL-6 levels, but not IL6 gene variants predict poor patient outcome following CABG.