Correlation of Mixed Venous and Central Venous Oxygen Saturation and Comparison between Venous-Oxygen Saturation and Cardiac Index

Background: Although mixed venous oxygen saturation(SvO₂) has been established as a useful measure of whole body oxygenation, SvO₂ must be measured through a pulmonary artery(PA) catheter. We performed this study to evaluate whether central venous oxygen saturation(ScvO₂) could substitute for SvO₂, and whether SvO₂ reflects cardiac output. Methods: Twenty five patients were studied. Thirteen patients(GA Group) had PA catheters inserted during general anesthesia, and twelve(ICU Group) patients in the intensive care unit had PA catheters inserted for management of critical illnesses. In each patient, blood samples for SvO₂ and ScvO₂ were drawn separately from the PA and CVP ports of a PA catheter, and cadiac index(CI) was measured. Results: Mean ScvO₂ was significantly higher than SvO₂ in both group, but the differences of SvO₂ and ScvO₂ were only about 2.5%. Correlations of SvO₂ and ScvO₂ were very high in GA and ICU Groups(r=0.92, 0.95, respectively). SvO₂ was weakly related to CI in GA Group(r=0.64), and in ICU Group(r=0.50) Conclusions: We conclude that ScvO₂ can be a useful estimate of SvO₂, but SvO₂ does not reliably reflect cardiac index. (Korean J Anesthesiol 1996; 30: 724-732)