To study the reliablity of MSFP and stressed volume to follow volume loading and to predict fload loading responsiveness in patients after elective coronary artery bypass grafting (CABG) surgery.

In this study the oesophageal Doppler monitor (CardioQ+), arterial pulse wave analysis (via the CardioQ+ and Flotrac device) and central venous pressure (CVP) will be used to estimate mean systemic filling pressure (MSFP) with the inspiratory hold method. Furthermore the MSFParm will be determined using a rapid cuff inflator. From MSFP vascular compliance (Csys) and stressed volume (Vs) will be calculated.

The accuracy of Vs to follow a 500 increase in volume will be studied. The accuracy of MSFP and Vs to to predict fluid loading responsiveness will be assessed in 42 patients after elective coronary artery bypass grafting (CABG) surgery. The effect of a standardised fluid loading on parameters of intrinsic contractility and afterload will be determined. The effect of fluid loading on inertia, resistance and elastance will be assessed

Inclusion Criteria:

• Patients 18 years and older planned for CABG

Exclusion Criteria:

• Contraindication for fluid loading
• Pregnancy, morbid obesity
• Hemodynamic instability with a mean arterial pressure (MAP) < 55 mm Hg and/ or a cardiac index < 1.5 L•min-1
• Severe arrhythmias
• Intra-cardiac shunts
• Symptomatic peripheral vascular disease
• Symptomatic pulmonary disease
• Significant valvular regurgitation
• Poor pre-operative left or right ventricular function
• Core temperature < 36 °C
• Contra-indication to the rapid cuff inflator
• Contra-indication to oesophageal Doppler probe insertion.

CABG