Minimal Volume for a Fluid Challenge in Septic Patients

Intravenous infusion of 2, 3, 4 or 5 ml/Kg of crystalloids over 5 minutes.

Measurement of stop-flow arterial-venous equilibrium pressure in the arm where the radial arterial pressure is measured by inflating a pneumatic cuff with an automatic pneumatic tourniquet during 60 seconds before and after the fluid challenge in patients receiving 2 ml/Kg, 3 ml/kg, 4 ml/kg and 5 ml/kg of crystalloids in 5 minutes