Ventricular Stimulation as Predictor of Hypovolemia After Cardiac Surgery

"Upon the return in intensive care:~* Baseline measurements: 1) Three measurements of blood pressure during inspiration and 3 during expiration will be collected for averaging systolic blood pressure, diastolic blood pressure, mean arterial pressure and ΔPP. Data from a pulmonary artery catheter will be also collected.~* Realization of VESAP pacing with adjustment of the pacemaker (PM) at a heart rate 5 bpm higher than the heart rate of the patient. After 20 seconds of stimulation, recording of the blood pressure curve as done at baseline during at least 3 respiratory cycles,~* Then vascular filling with 500 ml of physiologic saline solution over 10 minutes and new set of measurement (same than at baseline)~* Second realization of VESAP pacing, and new set of measurement (same than at Baseline)~* Then, if the ΔPP is \>10%, new vascular filling with 500 ml of physiologic saline solution over 10 min and new set of measurements as previously performed."