Comparative Evaluation of Central Venous Oxygen Saturation, Carbon Dioxide Venous Arterial Gradient, and Lactate Levels as Markers of Tissue Perfusion After Cardiac Surgery: A Prospective Exploratory Observational Study
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Objective
This study aims to identify which markers of tissue hypoperfusion—specifically lactate levels, central venous oxygen saturation (ScvO 2 ), and venous arterial carbon dioxide gradient (CO 2 gradient)—have the highest sensitivity and specificity in predicting the discharge of postoperative cardiac surgical patients from the ICU within 48 hours. This is an exploratory, hypothesis-generating investigation.
Methods
We conducted a prospective observational study involving 100 patients in the Surgical ICU at the Heart Institute of the Hospital das Clínicas, FMUSP, across two collection periods: February to September 2022 and February to June 2023. The study included patients who underwent surgical procedures requiring cardiopulmonary bypass. Comprehensive data on demographic, clinical, and laboratory variables were collected, focusing on tissue hypoperfusion markers measured at ICU admission and again 24 hours post-admission.
Results
Among the evaluated markers, ScvO 2 measured at 24 hours post-admission showed a statistically significant association with ICU discharge (odds ratio = 1.096, 95% confidence interval = 1.020–1.180, p = 0.012). Formal DeLong’s test confirmed ScvO 2 at 24h had significantly superior discriminatory performance compared to lactate (AUC 0.661 vs. 0.428; Z = 2.889; p = 0.004). In contrast, other markers—ScvO 2 at admission, lactate, and CO 2 gap—did not demonstrate significant associations in the exploratory multivariate analysis (p > 0.05).
Conclusion
In this exploratory cohort, ScvO 2 at 24 hours post-admission showed a statistically significant association with early ICU discharge and demonstrated superior discriminatory performance compared to lactate (DeLong p = 0.004). These findings are hypothesis-generating and require prospective validation in larger, adequately powered studies before clinical recommendations can be made.
