Differential Diagnosis for Acidotic Patient with Normal PO2 and PCO2 on VBG with Elevated CO

• Single Most Likely Diagnosis
  • Lactic acidosis: This is the most likely diagnosis due to the presence of acidosis with normal PO2 and PCO2 levels, suggesting a non-respiratory cause of acidosis. Elevated CO (carbon monoxide) can lead to tissue hypoxia, which in turn can cause lactic acidosis.
• Other Likely Diagnoses
  • Diabetic ketoacidosis (DKA): Although the primary cause of DKA is hyperglycemia, it can present with metabolic acidosis and elevated anion gap, similar to lactic acidosis.
  • Ethylene glycol or methanol poisoning: These substances can cause metabolic acidosis with an elevated anion gap and osmolal gap, which might be seen in the context of elevated CO levels if there is co-exposure.
• Do Not Miss Diagnoses
  • Carbon monoxide poisoning: While the question mentions elevated CO, it's crucial to consider the direct effects of CO poisoning, including tissue hypoxia and potential for cardiac and neurological complications.
  • Salicylate toxicity: Aspirin overdose can lead to a mixed acid-base disorder, including metabolic acidosis with respiratory alkalosis, but in the early stages, it might present with isolated metabolic acidosis.
• Rare Diagnoses
  • Pyroglutamic acidemia: A rare cause of high anion gap metabolic acidosis, often associated with acetaminophen use or malnutrition.
  • Maple syrup urine disease: A rare genetic disorder that can cause metabolic acidosis, although it typically presents in infancy.
  • Other organic acidemias: Various genetic disorders that affect the metabolism of organic acids, leading to their accumulation and resulting in metabolic acidosis. These are rare and usually present in early childhood.