Dynamic indices of preload dependence (such as stroke volume variability -SVV , pulse pressure variability - PPV and plethysmograph variability index - PVI ) are reportedly predictive of the response to vascular filling in sedated, mechanically ventilated patients. However, the influence of the sedation depth on these dynamic indices has never been evaluated.

Inclusion Criteria:

• All sedated, intubated, mechanically ventilated adult (over-18) patients admitted for elective cardiac surgery, monitored for sedation depth (with the BIS) and for preload dependence indices (SVV, PPV and PVI)
• Good echogenicity
• Social security coverage

Exclusion Criteria:

• Pregnancy, legal guardianship
• Subjects with black skin (a known technical limitation of plethysmography)
• Cardiac arrhythmia
• Sepsis
• Poor echogenicity

All sedated, intubated, mechanically ventilated adult (over-18) patients admitted for elective cardiac surgery, monitored for sedation depth (with the BIS) and for preload dependence indices (SVV, PPV and PVI)