Venous return is driven by the pressure gradient between mean systemic pressure and right atrial pressure. However, mean systemic pressure is more a physiological concept than an available clinical measurement. Indeed, the mean systemic pressure is the one that would be measured anywhere within the vascular system after cardiac arrest. Recent advances in hemodynamic monitoring have made MSP available to the clinician through beat-by-beat cardiac output measurements during respiratory pauses under mechanical ventilation. In this way, it is possible to calculate MSP, the pressure gradient and the venous return resistances. The investigators aim is to explain the hemodynamic variations and the decrease in cardiac output observed during prone position. The investigators hypothesis is that venous return resistances are increased during prone position probably following an increased intra-abdominal pressure.
Study Type
OBSERVATIONAL
Enrollment
40
University Hospital of Strasbourg
Strasbourg, France
mean systemic pressure variation
change of mean systemic pressure from supine position to prone position during surgery
Time frame: during surgery after the patient is put in prone position
intrathoracic pressure variation
Change of intrathoracic pressure from supine position to prone position during surgery
Time frame: during surgery during surgery after the patient is put in prone position
intravesical pressure variation
Change of intravesical pressure from supine position to prone position during surgery
Time frame: during surgery during surgery after the patient is put in prone position
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