• J Räsänen.
• Department of Anesthesiology, University of South Florida College of Medicine, Tampa.
• Chest. 1992 Apr 1; 101 (4): 1121-4.

AbstractTo assess the responsiveness of mixed venous oximetry under conditions of supply-independent and supply-dependent oxygen consumption, we subjected ten pigs to graded isovolemic hemodilution while measuring cardiopulmonary variables, including oxygen consumption (VO2), oxygen delivery (DO2), and mixed venous oxyhemoglobin saturation (SvO2). Supply-dependent VO2 was reached at an average hemoglobin concentration of 3.9 +/- 0.7 g.dl-1, an SvO2 of 38.2 +/- 8.1 percent, and an oxygen extraction ratio of 0.55 +/- 0.10. The change in SvO2 corresponding to a 100-ml decrease in DO2 was -9.2 +/- 3.7 percent when VO2 was supply-independent and -7.6 +/- 5.2 percent when it was supply-dependent (NS). However, the rate of decline in SvO2 in the supply-dependent range was significantly slower than the rate calculated assuming unchanged VO2 (-32.6 +/- 16.3 percent; p less than 0.01). The results indicate that appearance of supply-dependence of VO2 does not render mixed venous oximetry unresponsive to further deterioration of oxygen supply during isovolemic hemodilution.

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