Preoperative creatinine change and acute kidney injury by baseline kidney function after cardiac surgery

Preoperative kidney dysfunction is recognized as a predictor of acute kidney injury (AKI) after cardiac surgery, however, an important distinction regarding preoperative kidney dysfunction has often been neglected. This study aims to investigate the association between preoperative serum creatinine changes and AKI in varying baseline kidney function. This retrospective cohort study assessed patients who underwent open-heart surgery. Preoperative serum creatinine change (ΔScr) was calculated as the difference between the maximum preoperative serum creatinine values and baseline. Multivariate logistic regression was performed to evaluate the association between ΔScr and postoperative AKI in varying baseline kidney function. A total of 626 participants were included (median age 64 years, interquartile range 57–69), of whom 391 (62.5%) were male. Postoperative AKI occurred in 41.9% of patients after cardiac surgery. Compared with preserved eGFR (≥ 90 mL/min/1.73 m 2 ), moderately to severely reduced eGFR (< 60 mL/min/1.73 m 2 ) was associated with higher risks of both AKI and AKI non-recovery, whereas mildly reduced eGFR (60–89 mL/min/1.73 m 2 ) showed no significant association with either outcome. Across kidney function strata, higher ΔScr was associated with increased AKI risk in patients with preserved eGFR (adjusted OR, 1.40 per 0.1 mg/dL increase; 95% CI 1.13–1.74) and mildly reduced eGFR (adjusted OR, 1.66 per 0.1 mg/dL increase; 95% CI 1.42–1.93), but not in those with moderately to severely reduced eGFR. A similar pattern was observed for AKI non-recovery. When ΔScr was categorized, a small increase (0–0.3 mg/dL from baseline) was also associated with higher AKI risk in individuals with preserved and mildly reduced eGFR (adjusted OR, 2.56; 95% CI 1.45–4.52). Moderately to severely reduced eGFR was independently associated with AKI, whereas this association was not observed in preserved and mildly reduced eGFR. Elevation in preoperative serum creatinine was associated with AKI risk in preserved and mildly reduced eGFR.