Unexplained life-threatening high anion gap metabolic acidosis: the answer is in the urine!

A 49-year-old black male was referred to the Emergency Department (ED) after a 24-h history of confusion, progressive blurring of vision and altered mental status. On admission, the patient was confused and showed slurred speech and dyspnea. A history of alcohol abuse, and recent use of non-specified "energy drinks" was reported. The patient was apyretic; blood pressure was 170/80 mmHg, pulse rate 98 beats/min, respiratory rate 38 breaths/min, and peripheral oxygen saturation 99% at room air. Physical examination was unremarkable, but he showed progressive depression of cognitive status with no motor deficits nor nuchal rigidity. Brain CT scan was negative. Arterial blood gas showed high anion gap metabolic acidosis with slightly increased lactate levels (Table 1). Measured osmolality was 301 mOsm/kg, with no evident osmolal gap.