Relations between Mixed Venous Oxygen Saturation and Hemodynamic Variables in Patients Subjected to Abdominal Aortic Aneurysm Surgery and in Patients with Septic Shock

In order to study if oxygen saturation in mixed venous blood (SvO2) could be used as a marker for heart performance, oxygen delivery (DO2) or consumption (VO2) in critically ill patients 134 hemodynamic measurements were performed by a thermodilution pulmonary catheter in 23 patients after abdominal aortic aneurysm surgery. These data were compared to 200 measurements performed in 30 patients with septic shock. When analysed on an individal basis SvO2 was only closely related to DO2 or VO2 in a minority of the patients. Neither could SvO2 be used as a reliable marker for heart rate, hemoglobin concentration, stroke volume or cardiac index. On the other hand SvO2 was found to be an excellent marker for oxygen extraction (OER) in both groups of patients (median r=0.98. p < 0.0001). In conclusion, the present study shows that SvO2 could not be used as a reliable marker for the important hemodynamic variables Cl, DO2 or VO2 in critically ill patients. However, SvO2 was found to be an excellent marker for OER.