Objectives: To assess the predictive value of early postoperative perfusion markers (central venous oxygen saturation, lactate, and alactic base excess [ABE]) and Sequential Organ Failure Assessment (SOFA) scores in identifying patients at increased risk of postoperative complications following cardiac surgery.

Design: Single-center, retrospective observational study.

Setting: Cardiac surgery intensive care unit at a tertiary university-affiliated hospital in Europe.

Participants: 149 adult patients admitted after elective or urgent cardiac surgery.

Interventions: None.

Measurements and main results: Perfusion parameters and scores were recorded at admission, 6-12 hours, and 24 hours. The primary outcome was the occurrence of at least one major postoperative complication. In multivariable logistic regression, urgency of surgery (odds ratio [OR] = 7.214, 95% confidence interval [CI] 2.13-24.433; p = 0.001), occult hypoperfusion at admission (OR = 5.612, 95% CI 1.30-24.222; p = 0.021), hemoglobin at admission (OR = 0.955, 95% CI 0.926-0.985; p = 0.004), and SOFA score at 24 hours (OR = 1.470, 95% CI 1.224-1.764; p < 0.001) were independent predictors. Central venous oxygen saturation was not predictive; lactate showed a univariable association but was omitted from multivariable analysis to avoid collinearity with the composite occult hypoperfusion variable, which had a stronger univariable association. ABE at 24 hours showed a univariable association but was not independently predictive. The base prediction model showed excellent discriminative ability (area under the curve [AUC] = 0.871), good calibration (Hosmer-Lemeshow p = 0.221), and solid explanatory power (Nagelkerke R² = 0.517). In an extended prediction model, adding ABE at 24 hours yielded a similar AUC (0.875) without a significant improvement in discrimination, with modest gains in calibration and explained variance. Among individual variables, SOFA score at 24 hours had the highest AUC (0.79), providing the best balance of sensitivity (70.2%) and specificity (74.5%).

Conclusions: An integrative model combining urgency of surgery, hemoglobin at admission, occult hypoperfusion at admission, and SOFA at 24 hours provides robust day-1 risk stratification after cardiac surgery. These findings support the clinical utility of multimodal monitoring in the postoperative intensive care unit setting. ABE at 24 hours added acid-base and metabolic context, but it was not an independent predictor in this cohort.