Fluid REsponsiveness and Arterial ELASTANCE in Patients With Septic Shock or After Aortic Surgery

The MostCare system, thanks to the Pressure Recording Analytical Method (PRAM; Vygon, Padua, Italy), provides new hemodynamic parameters of the cardiovascular system. The PRAM method is a noncalibrated pulse contour method which requires only an arterial line (radial or femoral). This method has been validated in various clinical conditions. Among the collected parameters, some are well known and used daily care in Intensive Care Unit (ICU), i.e. cardiac output (CO), arterial pressure, heart rate, stroke volume (SV). Others such as arterial elastance (Ea) or dicrotic pressure are more recent and merit further investigation to determine their interest in clinical practice. To date, it is rarely used to adapt therapies, mostly because of a lack of knowledge regarding the evolution of these parameters. The aim of this study is to analyze the relationship between the evolution of Arterial Elastance and fluid responsiveness after a 250 mL fluid challenge of crystalloids in 5 minutes in patients with either septic shock or in the postoperative course of a major vascular surgery. Patients will be considered fluid responders if an increase \>10% of the stroke volume is observed .