Thiamine deficiency caused lactic acidosis in patient with malnutrition

: A case is presented, where preoperative malnutrition was the most likely explanation to elevated lactate levels during and after surgery. Poor circulation, a common cause of elevated lactate during surgery, was excluded. The elevated lactate levels were normalized after intravenous administration of thiamine. Thiamine is an essential cofactor in carbohydrate metabolism for energy production. Thiamine deficiency is common among ICU patients. Clinical suspicion of malnutrition should lead to early parenteral administration of thiamine without specific laboratory confirmation of thiamine deficiency.