IL6 and acute kidney injury: Our main findings are: (1) a greater percent decrease in plasma nitrite levels in the first 24 h was independently associated with the occurrence of POAF; (2) the AUC for the POAF model was significantly improved from 0.77 to 0.81 with the inclusion of reduced circulating nitrite levels as a reflection of increased oxidative stress; (3) the AUC of the AKI prediction model was improved from 0.69 to 0.74 with the inclusion of increased circulating IL-6 levels.