Increased Plasma Fibroblast Growth Factor 23 and In-hospital Acute Kidney Injury after Cardiac Surgery

Background: Acute kidney injury (AKI) occurs in 20 to 30% of cardiac surgery patients and is most often classified as mild. A previous study reported that intact fibroblast growth factor 23 (iFGF23) and C-terminal fibroblast growth factor 23 (cFGF23) measured after cardiopulmonary bypass (CPB) were associated with severe AKI after cardiac surgery but did not analyze the association between iFGF23 and all-stage AKI. The primary aim of the study was to determine whether FGF23 biomarker measurements 6 h after CPB were associated with all-stage AKI after cardiac surgery. Methods: This prospective observational study included 173 patients undergoing nonemergent coronary artery bypass graft (CABG) and/or valve surgery on CPB. The primary study outcome was all-stage postoperative in-hospital AKI defined using the Kidney Disease: Improving Global Outcomes serum creatinine criteria through postoperative day 7, or earlier if the hospital stay was less than 7 days. Plasma iFGF23 and cFGF23 were measured 6 h after the end of CPB. Results: A total of 32 patients developed in-hospital postoperative AKI (18.5%) by the seventh postoperative day. The incidence of AKI was 18.5% in CABG patients, 14.3% in valve surgery patients, and 41.2% in combined CABG valve patients. A two-fold increase in cFGF23 was associated with 1.57 greater predicted odds of developing in-hospital postoperative AKI (odds ratio [OR], 1.57; 95% CI, 1.26 to 1.96; P < 0.0001). This association remained significant after adjusting for clinical covariates (OR, 1.40; 95% CI, 1.10 to 1.77; P = 0.006) and after adjusting for preoperative Cleveland Clinic score (OR, 1.54; 95% CI, 1.22 to 1.95; P = 0.0003). A two-fold increase in iFGF23 was associated with 1.59 greater predicted odds of developing in-hospital postoperative AKI (OR, 1.59; 95% CI, 1.08 to 2.35; P = 0.018). Conclusions: Early postoperative measurements of cFGF23 and iFGF23 are associated with all-stage AKI after cardiac surgery. The utility of these biomarkers for risk classification in cardiac surgery patients remains to be determined.