Association of urinary ionomic profiles and acute kidney injury and mortality in patients after cardiac surgery.

Objective: The rarity of sensitive biomarkers for acute kidney injury (AKI) has impeded the timely therapy of AKI. Emerging evidence suggests that ion homeostasis may play pertinent roles in AKI. We aimed to screen out representative urinary ions and build a cardiac surgery-associated AKI indication model.

Methods: We performed urinary ionomic analysis from patients undergoing cardiac surgeries in Zhongshan Hospital, Fudan University, Shanghai, China (N = 261). By bioinformatics analysis, we identified differentially changed elements and established the AKI indication model we named the urinary ion index (UII). Follow-ups were performed to evaluate 30-day survival.

Results: The concentrations of most ions dynamically changed whether a patient developed AKI or not. A significant number of differentially changed elements between AKI and non-AKI groups were detected, especially at 2 hours after cardiac surgery, based on which we generated UII, with the area under the curve of 0.815 ± 0.006 and a cut-off value of 1.24. UII was associated with need for renal replacement therapy, with an area under the curve of 0.83 at a cutoff value of 1.62. Kaplan-Meier and log-rank methods, as well as Cox proportional hazards model, reflected that patients in the UII > 1.24 group had significantly higher risk of mortality within 30 days after surgery (hazard ratio, 5.15; P = .0097 and hazard ratio, 3.56; P = .033) than the UII ≤ 1.24 group.

Conclusions: Our data demonstrate that UII appears to be a novel and valid index of early cardiac surgery-associated AKI. UII > 1.24 at 2 hours after surgery indicates high risk of AKI and less 30-day survival.