1133

Abstract

Introduction: Type B lactic acidosis is a high-anion gap metabolic acidosis that occurs in the absence of tissue hypoxia. It involves the underutilization of lactate or compromised lactate metabolism. Liver disease, pyruvate dehydrogenase (thiamine) deficiency, inhibition of gluconeogenesis, and uncoupling of oxidative phosphorylation are the most common causes. We present a 4-year-old Caucasian male with medulloblastoma s/p resection undergoing treatment with Vincristine, proton beam therapy and steroids. He presented to the PICU with presumed septic shock that was treated with fluids, vasopressors, antibiotics and stress dose steroids. He was neutropenic and exhibited low-grade DIC. He demonstrated high-output renal failure with electrolyte wasting despite treatment. His mentation was impaired. His initial pH was 7.25 and his lactate ranged between10-12 mEq/L. An abdominal radiograph on admission was suggestive of pneumatosis. A subsequent CT scan of the abdomen did not reveal significant bowel inflammation or perforation. The patient improved and vasopressor support was stopped after 48 hours, yet his lactic acidosis persisted. Lactate levels peaked hospital day 3 at 19 mEq/L in the absence of hypoperfusion and was accompanied by profound hyperglycemia. A concomitant abdominal radiograph was suspicious for free air so the patient underwent exploratory laparoscopy that did not show evidence of ischemia or perforation. Because a type B lactic acidosis was suspected, intravenous thiamine and L-carnitine were given empirically and the lactate normalized over several hours, as did his urine output, and his mentation. Thiamine activity levels (transketolase activity in red blood cells) were not determined pre-therapy. The lactate/pyruvate ratio decreased to 10 from 20 after treatment. His risk factors for thiamine deficiency included malignancy, intractable emesis, and need for chronic total parenteral nutrition (TPN), which lacked MVI for several weeks due to national shortage. Thiamine is a cofactor for pyruvate dehydrogenase, which is a key enzyme in the anaerobic oxidation of glucose. The most dangerous sequela of thiamine deficiency is the CNS injury (Wernicke-Korsakoff syndrome). This patient recovered fully, finished his radiation therapy during his hospital course and was discharged. Patients receiving TPN without MVI supplementation are at risk for thiamine deficiency and its associated life-threatening complications.