The aim of the present study is to compare accuracy and precision of Cardiac Output (CO) by nine different pulse contour algorithms with transpulmonary thermodilution before and after cardiopulmonary bypass (CPB).

After induction of anesthesia, a central venous catheter and a transpulmonary thermodilution catheter (Pulsion Medical Systems, Munich, Germany) are introduced in the right internal jugular vein and in the femoral artery, respectively. The thermodilution catheter is connected to a PiCCO2 monitor (Software version 1.3.0.8). Thereafter, placement of an esophageal doppler probe is performed and the probe is connected to a unique Monitoring System (Deltex Medical, Chichester, UK) with nine different pulse contour algorithms. Cardiac Output by esophageal doppler is used to calibrate the nine different pulse contour algorithms.

After induction of anesthesia and establishment of all monitoring devices, a passive leg raising maneouvre (PLR) is performed and hemodynamic variables including CO by transpulmonary thermodilution (COTPTD) and CO by nine different pulse contour algorithms (COX1-9) are recorded before, during and after PLR. Subsequently, measurements of COTPTD and COX1-9 are carried out every 10 minutes until the beginning of CPB. Fifteen minutes after weaning from cardiopulmonary bypass calibration of nine different pulse contour algorithms by esophageal doppler are performed again and measurements of CITPTD and CIPFX are restarted up to the end of the surgical Intervention.

Inclusion Criteria:

• Patients > 18 years of age with a left ventricular ejection fraction ≥ 0.5.
• Patients undergoing coronary artery bypass grafting.

Exclusion Criteria:

• Patients <18 years of age and with a left ventricular ejection fraction ≤0.5 are not considered for the study.
• Emergency procedures and patients with hemodynamic instability requiring continuous pharmacologic support, intracardiac shunts, severe aortic-, tricuspid- or mitral stenosis or insufficiency and mechanical circulatory support were also excluded.