Thiamine vs. Placebo to Increase Oxygen Consumption After Cardiac Arrest

This study is to evaluate whether thiamine can increase oxygen consumption and lower lactate in patients who initially survive an in-hospital cardiac arrest. Patients who are successfully resuscitated after an in-hospital cardiac arrest and who are on mechanical ventilation in the intensive care unit will be enrolled, and will get either thiamine or placebo. Their oxygen consumption and lactate will be measured at serial time points and compared between groups. The investigators' hypothesis is that thiamine will help restore the body's ability to metabolize oxygen normally (aerobic metabolism), leading to an increase in oxygen consumption and a decrease in lactate.