Reliability and Accuracy of Mitral Velocity Time-integral Variability With Passive Leg Raising as a Marker of Preload-responsiveness in Patients With Acute Circulatory Failure in the ICU.

Adult patients with acute circulatory failure will be included in the study. An initial echocardiography is performed in patients placed in a semi-recumbent position. On the apical views (4 and 5-chamber views), the left ventricular outflow tract velocity time integral (LVOT-VTI) and mitral valve (MV-VTI) velocity time integral are measured (baseline values). Then a passive leg raise test is performed and the parameters (LVOT-VTI and MV-VTI) are measured again. Preload-responsiveness is defined by an increase in LVOT-VTI of at least 10%. In preload-responsive patients, a fluid loading with 500 ml of 0.9% saline administered over 15 minutes is performed. Immediately after fluid therapy, the same parameters are recorded during a third echocardiography. An increase of 10% or more of LVOT-VTI , compared with baseline, defines fluid responsiveness. Patients are monitored using the standard of care practices. Hemodynamic assessment includes repetitive echocardiographic examinations if needed. In patients with shock, invasive blood pressure is monitored with an arterial catheter.