Urinary interleukin-18 does not predict acute kidney injury after adult cardiac surgery: a prospective observational cohort study.

Introduction: Urinary interleukin-18 (IL-18) measured during the immediate postoperative period could be a promising predictor of acute kidney injury following adult cardiac surgery.

Methods: In a single-centre prospective observational cohort study, we enrolled 100 adult cardiac surgical patients undergoing cardiopulmonary bypass at a tertiary hospital. We measured the urinary concentration of IL-18 and creatinine preoperatively, on arrival in the intensive care unit, and 24 hours postoperatively. We assessed urinary IL-18 concentration and urinary IL-18/urinary creatinine ratio in relation to the postoperative development of acute kidney injury defined as an increase in serum creatinine of greater than 50% from preoperative to postoperative peak value within 48 hours after surgery.

Results: Twenty patients developed acute kidney injury. On arrival in the intensive care unit and at 24 hours postoperatively, urinary IL-18 (median [interquartile range]) was not different in patients who subsequently developed acute kidney injury compared with those who did not: on arrival in the intensive care unit (168 [717] versus 104 [256] pg/mL; P = 0.70) and at 24 hours (195 [483] versus 165 [246] pg/mL; P = 0.47). On arrival in the intensive care unit (area under the curve for the receiver operating characteristic curve [AUC-ROCC] 0.53, 95% confidence interval [CI] 0.38 to 0.68; P = 0.70) and at 24 hours postoperatively (AUC-ROCC 0.55, 95% CI 0.40 to 0.71; P = 0.48), urinary IL-18 was not better than chance in predicting acute kidney injury. All findings were confirmed when urinary IL-18 was adjusted for urinary creatinine. Urinary IL-18 correlated with duration of cardiopulmonary bypass (P < 0.001).

Conclusion: In adults, early postoperative measurement of urinary IL-18 appears not to be valuable in identifying patients who develop acute kidney injury after cardiac surgery, but rather represents a nonspecific marker of cardiopulmonary bypass-associated systemic inflammation.