Fluid responsiveness in a context of circulatory failure can be assessed by different way. Microcirculatory evaluation to assess fluid responsiveness could be interesting, but the available device are expensive and the analysis are delayed. Capillary refill time (CRT) is hampered by its variability. The investigators have developed a method to standardize the pressure, the length of compression and a computerized analysis to calculate the capillary refill time. This method enables accurate measure of CRT.

The investigators will study if CRT variation induced by a passive leg raising (PLR) can predict CRT after a 500 ml Fluid Load.

About thirty patients in circulatory failure with a continuous cardiac output monitoring for whom, the attending physician has decided a fluid load, will be included. hemodynamic parameters (arterial pressure, venous pressure, cardiac output), metabolic parameters (arterial and venous blood gas and lactate), microcirculatory parameters (assessed by sublingual video-microscopy) and capillary refill time measured on the thorax and on the gingival area will be recorded. Data collection will be made before and after a passive leg raising and after a 500 ml fluid load of crystalloids.

Patients will be aposteriori sorted in two groups: responders and non responders, defined by the reduction of CRT after the fluid load. The diagnosis ability of the CRT variation after PLR to predict in which group each patient is classified will be investigate and receiver operative characteristic curve will be built. These results will be compared to the metabolic response, the macrocirculatory response, and the microcirculatory response.

Inclusion Criteria:

• The patient is equipped with an arterial and a central venous catheter
• Capillary refill time is measurable.
• A cardiac output monitoring is available
• A 500 ml fluid load as been prescribed by the intensivist in charge.
• A circulatory failure is present defined as follow:

Patient treated with inotropic or vasoconstrictive drugs

OR

Patient presenting an hypotension defined by systolic arterial pressure less than 90 mmHg or mean arterial pressure less than 70 mmHg or a drop 40 mmHg in case of previous Hypertension.

WITH

tissue hypoperfusion defined by at least one of the following item:

• Lactate > 1 mmol/L
• Capillary refill time > 3 s
• Blotch
• Organ dysfunction due to the circulatory failure (oligo anuria, acute lung injury / acute respiratory distress syndrome, encephalopathy)

Exclusion Criteria:

• Pregnant woman
• Cardiogenic pulmonary edema
• Circulatory support : extracorporal life support / extracorporal membrane oxygenator, Thoratec, heart mate.
• Moribund patient
• Intra-abdominal hypertension
• Lower limb amputation

Patient hospitalized in our intensive care unit who are in circulatory failure and for whom the intensivist as decided to administer a 500 ml crystalloid infusion.