Does High-dose Vitamin B3 Supplementation Prevent Major Adverse Kidney Events During Septic Shock?

Inclusion Criteria: * Adult patients with septic shock defined as sepsis with persisting hypotension requiring vasopressors to maintain MAP ≥65 mm Hg and having a serum lactate level \>2 mmol/L (18 mg/dL) despite adequate volume resuscitation. * Written informed consent Exclusion Criteria: * Presence of inclusion criteria for more than 24 hours * Immediate indication to start renal replacement therapy at the time of randomization: Hyperkalemia≥ 6.5 mmol /l, metabolic acidosis with pH \<7.15 not controlled by medical treatment, diuretic resistant acute pulmonary edema or accumulation of a toxic requiring dialysis. * Formal indication of Nicotinamide supplementation according to the attending physician (eg pellagra, undernutrition, severe alcoholism) * Known severe chronic kidney disease (clearance \<30 ml /min) in the last 3 months preceding the setic shock or kidney transplant recipient. * Moribund patient (estimated survival less than 24 hours) * Patient who are not expected to survive to day 30 due to terminal-stage disease (terminal respiratory or heart failure, Child C cirrhosis, uncontrolled cancer) * Resuscitated cardiac arrest * Pregnant or lactating * Legal tutorship and guardianship * Lack of social security coverage.