Veno-arterial Carbon Dioxide Partial Pressure Difference (CO2gap) for Early Resuscitation of Septic Shock

Inclusion Criteria: * Patients aged 18 years or older AND * Acutely admitted to a study ICU AND * Primary diagnosis of septic shock according to the Sepsis-3 criteria and defined as: * A suspected or documented site of infection or positive blood culture AND * Acute increase of at least 2 points in the Sequential Organ Failure Assessment (SOFA) score consequent to the infection AND * Having a serum lactate level \>2 mmol/l AND * Requirement of vasopressors (any dose of norepinephrine) to maintain mean arterial pressure (MAP) ≥65 mmHg despite adequate fluid resuscitation (at least 1L of IV fluid in the last 24 hours prior to screening) Exclusion Criteria: * Septic shock for more than 12 hours at the time of screening * Primary cause of hypotension not due to sepsis (e.g., acute bleeding) * Decision not to resuscitate (or to limit full care) or not to intubate taken before obtaining consent * Death is deemed to be imminent or inevitable or patients with an underlying disease process with a life expectancy of less than 3 months * Anticipated surgery during the first 24 hours after randomization * Patient or their relatives' refusal to participate * Patients participating in another RCT with interventions possibly compromising the primary outcome * Prior enrollment in the CARBON trial * Known to be pregnant. * Legal protection (i.e., incompetence to provide consent and no guardian or incarceration) * No affiliation with the French health care system