The Case | Severe high-anion gap metabolic acidosis

An 80-year-old man was brought to the emergency department for decreased level of consciousness of 1-day duration. His past medical history was pertinent for hypertension, type 2 diabetes, chronic kidney disease stage 3a, and metastatic prostate cancer on palliative care. His medications included rosuvastatin, bisoprolol, prednisone, and daily acetaminophen for chronic pain. His past surgical history was relevant for transurethral resection of the prostate. On examination, the patient was hemodynamically stable but appeared weak and lethargic. The rest of his physical examination was unremarkable except for noted tachypnea.