Monitoring could secure management for patient but stay invasive. The purpose of this study was to compare,after cardiac surgery, the cardiac output measurement between transpulmonary thermodilution(reference method) and digital photoplethysmography (non invasive) for absolute value and dynamics changes before and after fluid expansion for patients with indication of fluid challenge.

• The time frame of the study period was included between the arrival at the ICU after cardiac surgery and before spontaneous breathing on mechanical ventilation
• Time-to-event outcome measures was period of time between the arrival at the ICU after cardiac surgery and before spontaneous breathing on mechanical ventilation. The event (hypotension) was defined as systolic arterial pressure under 90mmHg,less than 40mmHg, mean arterial pressure under 70mmHg, tachycardia upper 100 beats/min, presence of skin mottling, low cardiac output or previous blood loss.

Inclusion Criteria:

• Postcardiac surgery patients with arterial pressure monitoring and transpulmonary thermodilution monitoring with indication of fluid challenge
• Patients more than 18 years old

Exclusion Criteria:

• Patients under 18 years old
• Pregnant women
• Patient without invasive monitoring
• Urgency surgery

Post cardiac surgery intensive care patients with arterial pressure monitoring and transpulmonary thermodilution monitoring with indication of fluid challenge.