RApid Fluid Volume EXpansion in Patients in Shock After the Initial Phase of Resuscitation.

Rapid volume expansion using repeated intravenous fluid boluses is a very common intervention performed in the intensive care unit (ICU) in the early days of resuscitation of patients with shock. Once passed the initial phase of resuscitation, the fluid boluses administered fail to effectively increase the patients' cardiac output in about 50% of cases. Pulse pressure changes or stroke volume changes induced by a Passive Leg Raising (PLR) test have acceptable/good ability to predict fluid responsiveness (in terms of cardiac output change) and may be systematically used in patients with persistent shock with the aim of limiting the total amount of fluid administered to patients by avoiding undue fluid boluses. One may suppose that such a volume expansion management policy could impact morbidity and mortality of shocked patients. Among the predictive indices available in clinical practice, the PLR test has the advantages of being usable regardless of the patients' respiratory status and cardiac rhythm. Changes in left ventricular stroke volume during the PLR test perform better that changes in pulse pressure to predict fluid responsiveness. However, in counterpart, pulse pressure changes during PLR can be assessed without the need of other hemodynamic exploration such central venous pressure measurement or cardiac output monitoring. The investigators hypothesized that strategies using either stroke volume changes or pulse pressure changes induced by the PLR test to decide wether a fluid bolus clinically deemed indicated should or should not be administered, may limit the amount of fluid received by the patients during the first 5 days of shock, improve their oxygenation index, and shorten the time passed under mechanical ventilation, as compared to a "liberal" strategy (usual care) that does not use predictive indices of fluid responsiveness.