A comparison of central and mixed venous oxygen saturation in circulatory failure

The purpose of this study was to evaluate whether central venous oxygen saturation can be used as an alternative to mixed venous oxygen saturation in patients with cardiogenic and septic shock.

Prospective clinical study.

A tertiary intensive care unit in a university hospital.

Twenty patients with cardiogenic or septic shock requiring a pulmonary artery catheter and inotropic support.

None.

The central venous oxygen saturation overestimated the mixed venous oxygen saturation by a mean bias (or an absolute difference) of 6.9%, and the 95% limits of agreement were large (-5.0% to 18.8%). The difference between central and mixed venous oxygen saturation appeared to be more significant when mixed venous oxygen saturation was <70%. The changes in central and mixed venous oxygen saturation did not follow the line of perfect agreement closely in different clinical conditions. The central or mixed venous oxygen saturation had a significant ability to predict the status of cardiac output state, but this ability was reduced when the effect of hyperoxia was not considered.

Central and mixed venous oxygen saturation measurements are not interchangeable numerically.