Critical Care Medicine-Renal, Electrolyte and Acid Base Disorders>>>>>Acid Base Disorders
Question 2#

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
B. Starvation ketoacidosis
C. Lactic acidosis
D. Isopropyl ingestion
E. Propylene glycol toxicity

Correct Answer is A

Comment:

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.

Reference:

  1. Jacobsen D, Bredesen JE, Eide I, Østborg J. Anion and osmolal gaps in the diagnosis of methanol and ethylene glycol poisoning. J Intern Med. 1982;212(1):17-20.