Passive Leg Raising for Predicting Fluid Responsiveness in VA-ECMO Assisted Patients

Plain-language summary

Peripheral Veno-Arterial Extra Corporeal Membrane Oxygenation (VA ECMO) is a temporary assistance that provides a mechanical circulatory support in patients victim of cardiogenic shock (CS) or refractory cardiac arrest. During VA-ECMO support, hypotension may frequently occur due to deteriorated cardiac function, vasoplegia, or hypovolemia. Volume expansion is a common means to correct hypotension and improve systemic perfusion, but inappropriate fluid therapy is associated with adverse outcomes. As other intensive care unit (ICU) patients, VA-ECMO assisted patients have been shown to have higher mortality in case of large early fluid administration. Prediction of fluid responsiveness could achieve a lower fluid balance and improve outcomes of patients treated with VA-ECMO. Several dynamic hemodynamic parameters based on cardio-pulmonary interactions (stroke volume, pulse pressure or inferior vena cava variations induced by invasive ventilation cycles) have been described and validated for predicting fluid responsiveness in critically ill patients. Unfortunately, the VA-ECMO conditions (native cardiac circulation by-pass, low pulsatility, presence of drainage canulation in the inferior vena cava, the use of low tidal volume) make this parameters less reliable. Simulation of a fluid loading by shifting blood from the lower limbs and splanchnic compartment thanks to a revisable maneuver is another feasible approach to assess fluid responsiveness. Whereas the use of different maneuvers have been validated in the classical ICU population, very few data exist in the ECMO population and their application is questioning because blood transfer may be modified by the preload dependence of the ECMO. Recently, Luo et al showed that the variation of aortic Velocity Time Integral (VTI) measured using echocardiography induced by a Trendelenburg maneuver was predictive of fluid responsiveness during VA-ECMO support. However, their study excluded patients with low cardiac ejection (pulse pressure \< 15 mmHg) so that their data may not be extrapolated to the acute phase of heart failure requiring full mechanical support. Moreover, aortic VTI measurement suffers from low reproducibility in case of low native cardiac output (NCO) and arrythmia; and can be time-consuming. The investigators previously demonstrated in an observational prospective study that End-tidal CO2 (EtCO2) and Pulse Pressure (PP) were strongly correlated to NCO during VA-ECMO when NCO \< 2l/min. The investigators aim to study the variations of aortic VTI, EtCO2 and PP induced by Passive Leg Rising (PLR) and their ability to predict fluid responsiveness in patients under VA-ECMO.

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