Background

Acute kidney injury (AKI) is a common complication after pediatric cardiac surgery using cardiopulmonary bypass (CPB). This study evaluated renal regional oxygen saturation (R-rSO₂), measured via near-infrared spectroscopy (NIRS), as an AKI predictor.

Methods

120 pediatric patients undergoing CPB-assisted congenital heart surgery were prospectively enrolled. Continuous intraoperative R-rSO₂ monitoring was performed. Four multivariable logistic regression models (adjusted for age, pre-SCr, pre-hemoglobin, RACHS-2, cyanosis, and CPB time) assessed distinct R-rSO₂ metrics during CPB for predicting AKI (pRIFLE criteria).

Results

AKI incidence was 35.8% (n = 43). The model using the area under the curve (AUC) for R-rSO₂ decrease ≥5% during CPB showed superior predictive performance (C-index = 0.854) and fit. Within this model, a greater AUC for R-rSO₂ decrease ≥5% during CPB was independently associated with increased AKI risk (OR 1.02, 95% CI 1.00–1.03, P = 0.014). Prolonged CPB duration (OR 1.02, 95% CI 1.00–1.04, P = 0.028) and lower preoperative serum creatinine (OR 0.87, 95% CI 0.76–0.99, P = 0.031) were also significant predictors. AKI correlated with prolonged ventilation (P < 0.001) and higher costs (P < 0.001).

Conclusion

Renal tissue desaturation during CPB, quantified as the AUC for R-rSO₂ decrease ≥5%, is significantly associated with postoperative AKI in children. Higher preoperative creatinine (mature function) was protective, while longer CPB time increased risk.