Rational for the Use of Velocity-Pressure Loop in the Operating Room

In surgical patients considered with "high cardiovascular risk", by their field or by the nature of their intervention, it is recommended to use hemodynamic monitoring including a continuous measurement device of arterial pressure and cardiac output (CO). However, targeting mean arterial pressure (MAP) with boluses of selective peripheral vasopressors (without positive inotropic or chronotropic effects) could have deleterious effects on CO. Thus, it seems important to use a combined analysis of MAP and CO to estimate the afterload-related cardiac performance (ACP) The investigators recently proposed a cardiac afterload monitoring, in the descending thoracic aorta, based on a combined analysis of flow velocity signal recorded by trans-oesophageal Doppler and aortic pressure, the Velocity-Pressure Loop (VP Loop). VP Loop, and its derived indicators, especially Global AfterLoad Angle (GALA), could be useful during hemodynamic management for continuous cardiac afterload monitoring. However, in cardiology unit, cardiac afterload is usually measured at the ascending aorta behind the aortic valves. The main objective of this study is to compare VP Loop parameters build in the ascending and descending thoracic aorta according to patient cardiovascular risk factors.