To investigate the potential contribution of tissue oxygenation prediction in cardiac surgery–associated acute kidney injury (CSA-AKI) using near-infrared spectroscopy (NIRS) and serum lactate level measurements.

A retrospective study analyzing tissue oxygenation parameters and serum lactate levels during the perioperative period in patients undergoing cardiac surgery with cardiopulmonary bypass (CPB).

A single-center cardiac surgery unit in which patients underwent procedures requiring CPB.

A cohort of 391 patients who underwent cardiac surgery with CPB.

Measurement of brain tissue oxygen saturation (SctO₂) and skeletal muscle tissue oxygen saturation (StO₂) using NIRS. Perioperative serum lactate levels were collected through blood gas analysis via radial artery catheterization.

Tissue oxygen saturation measured by NIRS: During CPB, the SctO₂ cutoff was 56.75% and the StO₂ cutoff was 65.85%; after CPB, the SctO₂ cutoff was 60.15% and the StO₂ cutoff was 67.20%. These values demonstrate high predictive accuracy for CSA-AKI. Serum lactate levels: Postoperative levels ≥2.65 mg/L were independent predictors of CSA-AKI. Predictive model: The 5 independent significant variables combined had an area under the receiver operating characteristic curve of 91.8% (95% confidence interval, 0.762-0.887).

Tissue oxygen saturation measured during CPB and elevated postoperative serum lactate levels are valuable early parameters for predicting CSA-AKI risk in patients undergoing cardiac surgery with CPB. These findings highlight the clinical utility of these parameters in guiding early intervention strategies.