Evaluation of Doppler Flow From the Femoral Artery as a Reflection of Cardiac Flow in a Vascular Fluid Test

It is notable that in the intensive care patient, the ultrasound measurement of cardiac flow is not always possible, especially in case of mechanical ventilation, often responsible for air interposed between the ultrasound probe and the heart, thus stopping the ultrasound. Use the blood pressure increase as a reflection of the increase in cardiac flow induced by fluid replacement is not a fully satisfactory alternative since its performance is at best just acceptable. Flow measurement in the femoral artery could be an attractive alternative to the cardiac output measurement as: * It is easy: the femoral vascular ultrasound is booming with resuscitators, including the laying of intravascular catheter or thrombosis diagnosis. * It is painless: it is based on the application of the ultrasound probe on the root of the thigh for less than 5 minutes. * It is not subject to limitations echogenicity by interposition of air (except in exceptional circumstances) * It measures the same physiological parameter (arterial flow) as measuring ultrasound cardiac output (based on measurement of the flow at the outflow tract of the left ventricle). Pathophysiology study, multicenter (conducted in three French ICUs), open, prospective in order to evaluate the flow doppler from the femoral artery as a reflection of cardiac flow in a vascular fluid test in patient with signs of acute circulatory failure in intensive care unit.