Continuous cardiac output and mixed venous oxygen saturation monitoring

Continuous assessment of cardiac output and SVO2 in the critically ill may be helpful in both the monitoring variations in the patient's cardiovascula r state and in determining the efficacy of therapy. Commercially available continuous cardiac output (CCO) monitoring systems a re based on the pulsed warm thermodilution technique. In vitro validation s tudies have demonstrated that this method provides higher accuracy and grea ter resistance to thermal noise than standard bolus thermodilution techniqu es. Numerous clinical studies comparing bolus with continuous thermodilutio n techniques have shown this technique similarly accurate to track each oth er and to have negligible bias between them. The comparison between continu ous thermal and other cardiac output methods also demonstrates good precisi on of the continuous thermal technique. Accuracy of continuous oximetry monitoring using reflectance oximetry via f iberoptics has been assessed both in vitro and in vivo. Most of the studies testing agreement between continuous SVO2 measurements and pulmonary arter ial blood samples measured by standard oximetry have shown good correlation , Continuous SVO2 monitoring is often used in the management of critically ill patients. The most recently designed pulmonary artery catheters are now able to simultaneously measure either SVO2 and CCO or SVO2 and right ventr icular ejection fraction. This ability to view simultaneous trends of SVO2 and right ventricular performance parameters will probably allow the clinic ian to graphically see the impact of volume loading or inotropic therapy ov er time, as well as the influence of multiple factors, including right vent ricular dysfunction, on SVO2. However, the cost-effectiveness of new pulmon ary artery catheters application remains still questionable because no esta blished utility or therapeutic guidelines are available. Copyright (C) 1998 by W.B. Saunders Company.