Oxygen Consumption and Online Blood Gas Determinations during Rewarming on Cardiopulmonary Bypass

The online measurement of blood gases during rewarming on hypothermic CPB was performed with sensors utilizing optical fluorescence. In 20 patients, blood samples were obtained at 25°C. 30°C. 34°C and 36°C respectively for determination of oxygen content and calculation of VO2to determine the actual changes in VO2which occurred and to see if the continuous online measurements of blood oxygen tensions would provide useful information. VO2decreased to 31·28 ml/min/m2at 25°C. close to the predicted. With rewarming. VO2increased to 36% of predicted at 30°C. and at 36°C. was only 67% of predicted. Online measurement of PvO2provided a reasonably accurate reflection of the changing metabolic requirements during this period, more so than PaO2. These data suggest that the continuous measurement of blood oxygen tensions, particularly PvO2provides a simple and effective method of monitoring the adequacy of oxygen delivery.