Septic shock affections over 750,000 patients each year in the United States with an estimated 250,000 deaths. Septic shock may be characterized by hypotension, high metabolic state, lactic acidosis and potentially death. Vitamin B1 (thiamine) is a co-factor for pyruvate dehydrogenase, an essential enzyme for aerobic metabolism. In the absence of thiamine, the conversion of pyruvate to acetyl-CoA is inhibited and pyruvate cannot enter the tricarboxylic acid cycle (i.e., aerobic metabolism). With anaerobic metabolism predominating, ATP production is reduced, tissue hypoxia ensues, and pyruvate is converted to lactic acidosis. This failure to undergo aerobic metabolism, in turn, leads to hypotension (shock), multi- organ dysfunction, and ultimately death. Whether the provision of thiamine to patients in septic shock would provide a form of metabolic resuscitation through improving the efficacy of pyruvate dehydrogenase remains unknown. We hypothesize that the administration of intravenous thiamine to patients in septic shock will result in attenuation of lactic acidosis and a more rapid reversal of shock. We support this hypothesis through the following: 1) Thiamine is an essential co-factor for pyruvate dehydrogenase without which anaerobic metabolism predominates and lactic acidosis, shock, and death occurs if untreated (i.e., beriberi) 2) Intravenous thiamine rapidly reverses lactic acidosis and hemodynamic instability in thiamine deficient states (i.e., beriberi) 3) In the absence of thiamine deficient states, exogenous thiamine increases the activity of pyruvate dehydrogenase 4) In the absence of thiamine deficiency, intravenous thiamine attenuates acidosis and increases blood pressure in an animal model of septic shock 5) In patients with septic shock without significant liver injury, thiamine levels are negatively associated with lactic acidosis such that lower thiamine levels are associated with higher levels of lactic acidosis 6) In patients with septic shock, a small percentage of patients harbor clinically unrecognized absolute thiamine deficiency. Thus we propose the following prospective, double blind, two-center randomized trial of intravenous thiamine versus placebo in order to test our hypotheses. We believe the proposed study is highly innovative in that providing a form of metabolic resuscitation in septic shock is essentially a novel concept. Moreover, the results of this investigation are high yield in that there is currently no therapy available for treatment of metabolic dysfunction in shock. We will randomize a total of 88 patients who are in septic shock to receive either thiamine or placebo for seven days. Since intravenous thiamine has essentially no described side effects (save the extremely rare allergic reaction), the intervention has an even greater potential for efficacy and translation into clinical practice. PUBLIC HEALTH RELEVANCE: Septic shock affects over 750,000 patients each year with over 215,000 deaths. Thiamine (vitamin B1) is an essential component of cellular metabolism without which lactic acid build-up, low blood pressure, and death will ultimately occur. We believe that critically ill patients who receive thiamine will have improvement of blood pressure and acidosis that would ultimately translate to increased survival;thus, we will perform a randomized clinical trial to evaluate the effect of thiamine (versus placebo) for patients with septic shock.