We evaluate the accuracy of cardiac output measurement with esophageal Doppler ultrasonography (ECO). A total of 71 simultaneous measurement of esophageal Doppler and thermodilution cardiac output were compared in 16 patients undergoing general anesthesia in the supine position. ECO was determined easily with minimal experience, and significantly correlated with thermodilution cardiac output (TDCO) measurement ( P < 0.001). The regression equation obtained was Y = 0.983X + 0.019, and the correlation coefficient was 0.935. Furthermore, ECO was more reproducible than TDCO. However, ECO is not able to assess CO accurately in either lateral or prone position and after cardiopulmonary bypass in open heart surgery. Our results suggest that the esophageal Doppler technique allows a noninvasive and continuous cardiac output monitoring in patients during general anesthesia, and that it is more useful in patients for whom invasive monitoring is considered inappropriate. However, further improvement in this technique will be necessary for its routine use in clinical anesthesia.
Clinical evaluation of continuous SvO2 monitoring during general anesthesia was made in 21 surgical patients utilizing a fiberoptic reflectometry system combined with a pulmonary artery flow-directed balloon catheter. On-line in vivo values for SvO2 by the system were closely related to those obtained in vitro from a Radiometer ABL-300. There was a good correlation between changes of in vivo SvO2 and corresponding changes in cardiac index. We also observed that there were significant correlations between SvO2 and oxygen extraction ratio, and SvO2 and oxygen delivery. These data indicate that continuous monitoring of SvO2 during general anesthesia can provide on-line information not only about hemodynamic state but also on oxygen transport, which will be especially helpful in managing hemodynamically unstable patients during anesthesia.
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