"Mini Fluid Challenge Assessment: a Comparison Among Three Hemodynamic Tools"

The mini fluid challenge (mini\_FC) is a functional hemodynamic test which has been used in different clinical contexts to assess fluid responsiveness.

This test is performed by rapidly injecting a small aliquot of fluid (100 ml over 1 minute), which is followed by the infusion of the residual aliquot of fluid.

Since the threshold of the mini\_FC identified by the literature is rather small (5% of stroke volume (SV) increase after the 100 ml bolus to discriminate between responder and non-responder), it is crucial that the hemodynamic tool assessing this change could be reliable. Moreover, the SV changes with inspiratory/expiratory movements and the increase after the mini\_FC should also consider the physiological fluctuations of the SV.

In the literature this test has been performed by means of tolls with different least significant change of the SV. The least significant change (LSC) represents the smallest difference between successive measurements of SV that can be considered to be a real change and not attributable to chance.

The purpose of this study is to assess the agreement among MOSTCARE system (4.5\& of SV LSC described in the literature) and the echocardiography (about 10% of SV LSC described in the literature) with the PICCO system (about 1% of SV LSC described in the literature - considered the gold standard) in discriminating fluid responsiveness after a mini\_FC