Association of cardiac biomarkers with acute kidney injury after cardiac surgery: a multicenter cohort study

Background — Acute kidney injury (AKI) is common after cardiac surgery and is associated with post-operative mortality. Perioperative cardiac biomarkers may predict AKI and mortality.

Objective — We evaluated whether cardiac biomarkers were associated with severe AKI, defined as a doubling in serum creatinine or requiring renal replacement therapy during hospital stay after surgery, and mortality.

Methods — In a prospective multicenter cohort of adults undergoing cardiac surgery, we measured the following biomarkers in pre- and post-operative banked plasma: high-sensitivity troponin T (hs-cTnT), troponin I (cTnI), CK-MB and NT-proBNP.

Results — In the patients who were discharged alive, severe AKI occurred in 37/960 (3.9%) and 43/960 (4.5%) died within 1 year of follow-up. NT-proBNP was the only pre-operative biomarker that was independently associated with severe AKI (with log transformation, adjusted OR=1.4, 95% CI (1.0, 1.9)). Biomarkers measured within 6 hours of surgery (Day 1) were all associated with severe AKI. Pre-operative NT-proBNP was also independently associated with 1-year mortality (with log transformation, adjusted OR=1.7, 95% CI (1.2-2.2)). Patients in the highest tertile for NT-proBNP pre-operatively (>1006.4 ng/L) had marked increases in their risk for 1-year mortality (adjusted OR=27.2, 95%CI (3.5-213.5)). Day 1 NT-proBNP was associated with mortality independently of change in serum creatinine from pre-operative baseline.

Conclusion — Of the studied biomarkers, NT-proBNP was the only pre-operative biomarker independently associated with severe AKI and mortality. Early increases in post-operative cardiac biomarkers were associated with severe AKI after cardiac surgery. Future research should focus on whether interventions that lower NT-proBNP can impact upon post-operative outcomes.