There are no available criteria for determining the optimal flow rate and mean arterial pressure level in patients under cardiopulmonary bypass (CPB). Transcutaneous carbon dioxide tension (PtCO2) has been proposed for microcirculation monitoring and it could be useful for guiding hemodynamic optimization under CPB. The goal of this exploratory study was to determine the factors that influence PtCO2 variations during CPB.

DESIGN: Cutaneous ear lobe CO2 tension was monitored along with hemodynamic parameters every 10 minutes during CPB, until aortic unclamping. SETTING: French university teaching hospital PARTICIPANTS: Patients scheduled for cardiac surgery requiring CPB were prospectively included.

Inclusion Criteria:

• Patients scheduled for cardiac surgery under cardiac arrest and cardiopulmonary bypass were prospectively included in the present observational study conducted at a French teaching hospital.

Exclusion Criteria:

• The exclusion criteria were: age <18, pregnancy, septic or emergency surgery.

Patients scheduled for cardiac surgery under cardiac arrest and cardiopulmonary bypass were prospectively included in the present observational study conducted at a French teaching hospital.