Mixed venous oximetry.

We now have the technology through reflectance spectrophotometry to evaluate and display continuously mixed venous oxygen saturation SvO2 through use of a modified pulmonary artery catheter. Adding this method of assessing the balance of oxygen supply and demand to our standard armamentarium of hemodynamic monitoring may improve our ability to diagnose and treat cardiovascular aberrations at an earlier stage than was previously possible. Through analysis of the Fick equation, it can be seen that SvO2 depends upon the cardiac output, the arterial oxygen saturation, the hemoglobin level, and the rate of oxygen consumption. These are, in turn, affected by a great number of factors (see Fig 8). As seen in the variety of patient care examples cited above, the usefulness of SvO2 monitoring continues to grow. It appears that there are no intrinsic risks associated with SvO2 monitoring beyond those of customary PA monitoring. This new technology provides us with online information not previously available, at an associated cost that needs to be further examined.