Hypercapnia prevents jugular bulb desaturation during rewarming from hypothermic cardiopulmonary bypass

Background: The rewarming period of hypothermic cardiopulmonary bypass (CPB) is associated with reduced jugular bulb venous oxygen saturation (SjO(2)). This study investigates the effects of normocapnia vs, hypercapnia on changes in SjO(2) during rewarming from hypothermic CPB for coronary artery bypass graft in patients classified as American Society of Anesthesiologists physical status III. Methods: Anesthesia was induced and maintained with fentanyl, midazolam, and continuous infusion of etomidate. Hypothermic CPB (27 degrees C) was managed according to alpha-stat conditions. The SjO(2) percentage was measured using a fiberoptic catheter placed in the right jugular bulb via the right internal jugular vein. Data mere recorded before and during the rewarming period, Patients were assigned to a normocapnic (Pa-CO2: 36-40 mmHg, n = 10) or hypercapnic (Pa-CO2: 45-50 mmHg, n = 10) Pa-CO2 regimen during rewarming. Results: The maximum reduction of SjO(2) occurred during rewarming with the jugular bulb temperature at 35-36 degrees C. In contrast, SjO(2) did not change during rewarming from hypothermia in hypercapnic patients. Conclusions: These results show that mild hypercapnia prevents the desaturation of SjO(2) seen with the normocapnic group during the rewarming period from hypothermic CPB. These data suggest that mild hypercapnia during rewarming from CPB is associated with a better balance between cerebral oxygen supply and demand.