[Analysis of risk factors for acute kidney injury following reoperative cardiac surgery].

Objective

To identify perioperative risk factors associated with postoperative acute kidney injury (AKI) following redo cardiac surgery, with an emphasis on the roles of operative strategies.

Methods

This is a retrospective case control study. A retrospective analysis was conducted on the clinical data of 293 patients who underwent redo cardiac surgery at Nanjing First Hospital between January 2016 and September 2025. There were 140 male cases, 153 female cases, aged (M(IQR)) 61(17) years (range:22 to 82 years). Patients were divided into AKI (n=158) group and non-AKI group (n=135). The comparison of data between the two groups was conducted using independent sample t test, Mann-Whitney U, χ2 test or Fisher's exact probability method,respectively. Univariable and multivariable Logistic regression analyses were performed to identify potential risk factors for AKI and to assess their independent associations. A mediation model was further established to explore whether prolonged cardiopulmonary bypass (CPB) time mediated the relationship, aiming to elucidate mechanisms in the context of redo cardiac surgery.

Results

Advanced age (OR=1.03,95%CI:1.01 to 1.05,P=0.008), history of diabetes (OR=3.95,95%CI:1.66 to 9.37,P=0.002) and atrial fibrillation (OR=1.94,95%CI:1.10 to 3.42,P=0.022), prolonged CPB time (OR=2.09,95%CI:1.53 to 2.86,P<0.01), increased intraoperative blood transfusion volume (per 100 ml,OR=1.06,95%CI:1.03 to 1.10,P=0.011) were identified as independent risk factors for AKI. Increased intraoperative urine output was identified as an independent protective factor against postoperative AKI (per 100 ml, OR=0.96,95%CI:0.92 to 0.99,P=0.032). Mediation analysis indicated that the relationship between early CPB institution before sternal re-entry and AKI may be partially mediated by prolonged CPB duration, the average causal mediation effect was 0.041(95%CI: 0.012 to 0.080,P=0.004).

Conclusions

The incidence of AKI is relatively high after redo cardiac surgery. Minimizing CPB time, reducing transfusion during surgery may serve as an important strategy to reduce the risk of AKI.