Pharmacodynamic Analysis of the HaemOdynamic Effects of a Standard Fluid BolUS

When the flow of blood ejected by the heart drops significantly, that is to say when there is "shock", one of the first treatments undertaken is often volume expansion. This treatment consists of injecting a liquid intravenously, generally in the form of a bolus, that is to say a dose of solute administered all at once, of 250 to 500 mL of fluid over approximately 10 to 30 minutes. The injected fluid expands the blood volume and fills the heart pump, in order to increase the flow it ejects. However, this treatment poses two problems. First, it is only inconsistently effective. It is possible that of the 250-500 mL of fluid administered in the standard way, only a part is effective, whereas, as the effectiveness decreases during the infusion, the rest does not increase cardiac output significantly. However, the average part of the total volume that is ineffective on a large population of patients is not well known. Second, the effects of volume expansion on cardiac output decrease rapidly after the end of administration. However, the average duration of effectiveness of a 250-500 mL fluid bolus, and the factors that influence this duration of effectiveness, are not well determined. The main objective of this research is to measure, among the volume of a fluid bolus, which part does not significantly increase cardiac output. The secondary objective is to measure the average time of effectiveness after the end of the infusion and the factors that influence it.