Correlation between central venous oxygen saturation and oxygen delivery changes following fluid therapy

Background: The rationale for using central venous oxygen saturation (ScvO₂) in various clinical scenarios is that it reflects the balance between oxygen delivery (DO₂) and demands. In this study, we evaluated the correlation between ScvO₂ and DO₂ changes (ΔDo₂, ΔScvO₂) in patients receiving fluid therapy following coronary surgery. We also correlated the changes of mean arterial pressure (ΔMAP) and central venous pressure (ΔCVP), with ΔDO₂. Methods: Sixty consecutive sedated and mechanically ventilated adult patients, with cardiac index ≤2.3 L/min/m² and a pulmonary artery occlusion pressure ≤12 mmHg following coronary surgery, were included. Concomitant hemodynamic parameters, arterial and venous blood gases were measured before (T0) and after (T1) administration of a 500 ml bolus of an isotonic crystalloid solution over 30 min. The correlations between ΔDO₂ and ΔScvO₂, ΔMAP or ΔCVP were evaluated by linear regression analysis and Pearson test. Results: Cardiac index (1.9±0.2 vs 2.3±0.5 ml/min/m²), MAP (83±11 vs 94±13mmHg) and CVP (5.7±3 vs 7.1±3 mmHg) were significantly higher at T1 compared with T0. The correlation of ΔDO₂ with ΔScvO₂ was positive, significant (r=0.41; P=0.004) and superior to its correlation with ΔMAP (r=0.30; P=0.01) or ΔCVP (r=0.03; P=0.78). Conclusion: A significant correlation between ScvO₂ and DO₂ changes was found in patients receiving fluid therapy following coronary surgery. ScvO₂ could be used as an indicator to track DO₂ and to guide volume loading.