Correlation of Whole-Body Oxygen Consumption with Mixed Venous Blood Temperature During Hypothermic Cardiopulmonary Bypass in Man

The correlation between whole-body oxygen consumption and mixed venous blood temperature was investigated in ten adult patients during hypothermic cardiopulmonary bypass. The perfusion flow was maintained constant at 2.4 L/min/m2 during cooling and rewarming. Mixed venous blood temperature was continuously monitored during bypass at the venous inlet of the oxygenator. The mixed venous blood temperature was decreased to 25-28°C. During rewarming, at every two degree increase in temperature, blood samples were withdrawn simultaneously from the arterial and venous ports of the oxygenator for blood gas analysis. Whole body oxygen consumption (arterial-venous oxygen content difference multiplied by the perfusion index) was calculated at the different mixed venous blood temperatures. The whole-body oxygen consumption showed a linear correlation with the venous blood temperature on a semi-logarithmic scale. The Q10 (the ratio of oxygen consumption at two temperatures separated by 10°C) was approximately 2.0, which is in agreement with Van’t Hoff’ s rule describing the effect of temperature on the equilibrium constant of a chemical reaction