Demir, Özge; Üstündağ, Hilal; Onk, Oruç Alper

Background: Postoperative cognitive dysfunction (POCD) is a significant complication of coronary artery bypass grafting (CABG), with impaired quality of life and long-term outcomes. The association between postoperative arterial blood gas (ABG) abnormalities and early cognitive outcomes remains unclear. Objectives: To investigate the association between perioperative ABG parameters and SMMSE-assessed cognitive function in patients undergoing elective CABG. Methods: This prospective study of 41 CABG patients recorded SMMSE scores and ABG parameters (pH, PO₂, PCO₂, HCO₃⁻, SO₂, base excess) preoperatively and 3–7 days postoperatively; POCD was defined as a ≥ 2-point SMMSE decline. Analyses included correlation, regression with VIF diagnostics, logistic regression, ROC analysis, and FDR correction. Results: Age was 63.15 ± 7.42 years; 29 of 41 patients (70.7%) met POCD criteria, with SMMSE declining (p < 0.001). Postoperative pH, PO₂, SO₂, HCO₃⁻, and base excess correlated with SMMSE change (ρ = 0.567–0.608, all p < 0.001) and differed between groups (all p ≤ 0.003); PCO₂ showed neither association. In multivariable regression, the model was significant (adjusted R² = 0.332, p = 0.002), but no individual parameter remained significant, reflecting multicollinearity (VIF up to 5.21); these also predicted POCD by logistic regression, and ROC analysis identified HCO₃⁻ as the strongest discriminator (AUC = 0.885), followed by pH (0.866) and base excess (0.851). Conclusions: Postoperative ABG derangements, metabolic acidosis and hypoxemia, are significantly associated with early cognitive decline after CABG. No single parameter was an independent predictor, reflecting interrelation; pH, HCO₃⁻, and base excess showed the strongest discriminative accuracy. These observational associations warrant confirmation in interventional studies.