This is a transversal study allowing to compare the microcirculatory reactivity before and after a 30-minute intravenous infusion of 40 mg/kg vitamin C.~Design:~• A monocentric, open-label, transversal study~Sample size :~30 patients~Assessement:~Between 6 hours and 24 hours after admission, the patient will be included after collection of the non opposition.~There will be two evaluation times: T0 before the start of vitamin C's perfusion, and T1: 1 hour after the end.~No interim analysis is planned. Analysis will be performed at the end of the study after data review and freezing of data base.
Compare the microcirculatory reactivity before and after a 30-minute intravenous infusion of 40 mg/kg vitamin C and evaluate intra-individual variation of hemodynamic parameters between T0 and T1.