This week’s edition of the Step 1 Question of the Week is about biochem. See if you can answer the question and then watch the video to learn the correct answer as well as the rationales for each option.
An 89-year-old man is brought to the emergency department from a nursing home with a 2-hour history of severe abdominal pain and bloody stool. He has a history of type 2 diabetes mellitus, myocardial infarction, hypertension, dyslipidemia, and atrial fibrillation. His pulse is 120/min, and blood pressure is 90/59 mm Hg. Physical examination reveals left-upper-quadrant abdominal tenderness, guarding, and rigidity. The urinalysis is negative for blood, protein, and glucose. An arterial blood gas shows pH of 7.30, HCO3– of 12 mEq/L, PCO2 of 25 mm Hg, and PO2 of 82 mm Hg.
Excess of which of the following acids characterizes the most likely diagnosis in this patient?