In ICU, fluid challenge represents one of the cornerstones of hemodynamic care. However, fluid overload due to an excessive and/or inappropriate fluid administration could be associated with morbidity or mortality. Unfortunately, there is currently no continuous non-invasive devices to monitor fluid content at bedside. Bio reactance is a non-invasive, rapid and continuous technology developed in order to measure body fluid compartment. Monitoring devices functioning with such technology are promising to evaluate fluid overload in ICU.