Venous to Arterial Carbon Dioxide Difference (P₍ᵥ-ₐ₎CO₂): Predictor of Septic Patient Prognosis Depending on the ScvO₂

the investigators will include 120 patients with a diagnosis of septic shock in accordance with the definition given by the 2001 expert consensus. Two groups of patients are likely to participate in this study: Patient hospitalized in intensive care for a septic shock = Primary patient + patient who develops, the waning of his hospitalization in intensive care for another reason, a septic shock = Secondary patient. Haemodynamic monitoring by transpulmonary thermodilution allow a patient's close monitoring during the initial phase supported. The clinical and biological data, demographic and the severity scores are collected for each patient during the first three days of stay. To predict the unfavorable evolution of the patients, a measure of the SOFA score at the input (J0) and third day (J2) is performed. the investigators analyzed mortality at day 28 in patients with increased P₍ᵥ-ₐ₎CO₂ and those with increasing of organ failure. This research will be conducted according to good clinical practice. An information will be distributed to patients.