Thiamine as an Adjunctive Therapy in Cardiac Surgery

The main purpose of this pilot study is to test the effects of thiamine (vitamin B1) administration before and after major cardiac surgery. Half of patients will receive thiamine and the other half will receive placebo. The investigators' main hypothesis is that thiamine will improve cellular oxygen consumption and lead to decreased levels of post-operative lactate levels and ultimately improved patient outcomes.

Over 230,000 patients in the United States undergo Coronary Artery Bypass Grafting (CABG) each year. While mortality is relatively low, morbidity remains substantial with a significant risk of prolonged time on mechanical ventilation, prolonged length of hospital and intensive care unit stay and many other complications. CABG causes a profound stress response and significant metabolic alterations occur, including a shift from aerobic to anaerobic metabolism, causing increased levels of pyruvate and lactate. Elevated lactate, a marker of anaerobic metabolism, is a common and significant finding in patients after CABG and is correlated with increased mortality and morbidity. Aerobic metabolism occurs when pyruvate enters the mitochondria through pyruvate decarboxylation to acetyl-Coenzyme A, facilitated by the enzyme pyruvate dehydrogenase (PDH). Decreased PDH activity may cause a shift toward anaerobic metabolism and play a role in the changes seen in patients undergoing CABG. Thiamine (vitamin B1) is a key co-factor for PDH function and will increase activity even in non-deficient states. The investigators hypothesize that thiamine administration will increase PDH activity in patients undergoing CABG, leading to increased cellular oxygen consumption, as represented by decreased lactate levels after surgery, and ultimately improved clinical outcomes. In order to test the investigators' hypothesis and to obtain data for a large-scale clinical trial evaluating relevant clinical endpoints, the investigators are conducting a randomized, double-blind, pilot trial of thiamine in high-risk patients undergoing CABG.