MEDizzy - A 30-year-old male is brought to the emergency room from

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Nephrology

A 30-year-old male is brought to the emergency room from prison, where he works in the paint shop. He is barely arousable but has no focal abnormalities. He has no past medical history. CT scan of the head is nor- mal. Urine toxicology screen is negative. Ethanol and acetaminophen are not detectable. Laboratory data is as follows: Na: 140 mEq/L K: 5.1 mEq/L Cl: 100 mEq/L HCO310 mEq/L Creatinine 1.2 mg/dL Blood ethanol: nondetectable Blood glucose: 110 mg/dL Arterial blood gases: PO2 88, PCO2 23, pH 7.21 Which of the following tests will provide the key to correct diagnosis?

ExplanationThis patient appears intoxi- cated and has a severe anion gap acidosis (AG = 30 mEq/L). This scenario suggests toxic alcohol ingestion, and the osmolar gap should be calculated. The estimated plasma osmolality is calculated as follows: 2×Na+BUN/2.8+ glucose/18+blood ethanol/4.6 (denominators are a function of molecular weight of each substance). Here the calculated osmolality is 288 mOsm/L (2 × 138 + 14/2.8 + 90/18 + 0/4.6). This patient is found to have a measured plasma osmolality of 320 mOsm/L. The measured osmolality of 320 mOsm/L minus the calculated osmolality of 288 mOsm/L gives an osmolar gap of 32 (normal less than 10) due either to methanol or ethylene glycol. In this case, methanol, used in paint thinners, is likely. Ethylene glycol, used in antifreeze, is frequently associated with hypocalcemia, renal failure, and crystalluria. Serum ketones should be checked, but diabetic ketoacidosis is unlikely with a blood sugar of 110 mg/dL, and alcoholic ketoacidosis rarely, if ever, causes acidosis of this severity. Serum lactate should be checked, but in an afebrile patient with normal blood pressure, lactic aci- dosis is unlikely to be the primary cause. Rhabdomyolysis does not cause a wide anion gap metabolic acidosis; so a CK level would not be helpful. A primary CNS event would not account for this patient’s wide anion gap metabolic acidosis.