Correlation between Central Venous - Arterial Carbon Dioxide Tension Gradient and Oxygen Delivery Changes Following Fluid Therapy

Background: Central venous-arterial carbon dioxide (CVA-CO2) tension gradient was related to low cardiac output after coronary surgery. The objective of this study was to assess the correlation between CVA-CO2 tension gradient and oxygen delivery (DO2) changes following fluid therapy in coronary surgery. Methods: A prospective interventional study was conducted in a cardiac surgery intensive care unit. Forty consecutive sedated and mechanically ventilated adult patients, with a cardiac index < 2.3 L/min/m² and a pulmonary artery occlusion pressure ≤ 12 mmHg following coronary surgery, were included. All patients received a 500 ml bolus of an isotonic crystalloid solution over 20 min. Concomitant hemodynamic parameters, arterial and central venous blood gases were measured before (T0) and after (T1) volume loading. Means were compared by Student’s test and correlations by Spearmen coefficient”. P ≤ 0.05 was considered to be significant. Results: CVA-CO2 gradient decreased (12.6 ± 3.0 vs 10.2 ± 3.7 mmHg; p = 0.01) and DO2 increased (312 ± 57 vs 357 ± 81 l/min/m²; p = 0.001) significantly from T0 to T1. The correlation between CVA-CO2 gradient changes and DO2 changes was negative and statistically significant (r = -0.38; p=0.015). Conclusion: CVA-CO2 gradient and DO2 changes were inversely and significantly correlated in patients receiving fluid therapy following coronary surgery. In this context, CVA-CO2 gradient changes could be used as an indicator to guide volume loading and to assess its effect on DO2.