A 43-year-old man is brought by the police to the emergency department after being found unresponsive on the street. He appears unkempt and disheveled. On physical examination, his temperature is 36.0°C, blood pressure is 146/92 mm Hg, pulse rate is 84 beats/min, and respiratory rate is 10 breaths/min. He is not oriented to time and place. Laboratory data show the following:
An arterial blood gas is also obtained which shows:
Which of the following is the MOST likely diagnosis in this patient?A. Ethylene glycol poisoning
Correct Answer: A
The patient presents with an increased anion gap metabolic acidosis of 28—calculated anion gap = Na − (HCO3 + Cl). In addition, his serum bicarbonate level is reduced to 8 mEq/L with a plasma osmolal gap of 12 mOsm/kg H2O. Altogether, this points to ethylene intoxication. The osmolal gap is defined as the difference between the measured and the calculated plasma osmolality using the formula below:
Calculated plasma osmolality = (2 × plasma sodium) + glucose/18 + BUN/2.8
Ethylene glycol is commonly found in automotive coolants and cleaners, and ingestion of ethylene glycol will cause an increased anion gap metabolic acidosis with increased plasma osmolal gap of >10 mOsm/kg H2O. Of note, methanol poisoning will also lead to similar findings. Isopropyl poisoning will also have an increased osmolal gap of >10 mOsm/L, but it does not usually cause an anion gap metabolic acidosis.