Toxicology Answer: An Illustrated Case of Ethylene Glycol, Direct and Indirect

Ethylene glycol (EG), also known as ethane-1,2-diol, with the molecular formula CH2OHCH2OH, is a colorless, odorless, water-soluble liquid commonly used as antifreeze fluid in automobile radiators, and remains an important cause of significant and sometimes fatal toxicity in the United States, with approximately 6,000 exposures and 20 deaths reported to poison centers in 2021.1 After possible exposures, early diagnosis and treatment are critical for preventing morbidity and mortality. However, the diagnosis of EG exposures continues to be problematic due to inconsistent history, restricted availability of EG-specific testing, and inconsistent time-sensitive indirect clues in laboratory analysis.

A young adult male with a prior history of self-harm presented 30 minutes after stating he “might have drunk half a gallon of antifreeze.” Physical examination revealed an awake, anxious-appearing, tachycardic man with no other abnormalities. Laboratory data were notable for normal renal function, osmol gap 24 (normal range, -14 to +10), anion gap 10 (normal range, 3 to 13), and normal urine without crystals. He was empirically loaded with fomepizole (15 mg/kg). The patient’s urine was obtained and compared with the urine of his emergency physician using a Wood’s lamp, and the patient’s was found to be brightly fluorescent, supporting the presumptive diagnosis of EG poisoning. After 12 hours, his initial EG level returned 130 mg/dL. After resolution of EG poisoning, he was transferred to psychiatry and ultimately discharged home without complication.

The diagnosis of EG ingestion is problematic, often made on suggestive indirect information, and must be made quickly because time represents renal injury. The bedside physician must gather as many direct and indirect, classically suggestive data as possible and decide which are “bad” (they probably drank it), or “good” (they probably didn’t). The presence of urine fluorescence might be additive to this data collection.

Someone saw them drink the EG. This is bad (direct evidence). Their experience drinking the liquid. For example:

Doctor: “I bet it was terrible when you drank it, huh?”

Patient: “You know Doc, it wasn’t so bad, actually sort of sweet.”

This is bad (indirect evidence).

Osmol gap: If the gap is large—this is bad (indirect evidence). However, it is the parent alcohol that causes the gap, and with a typical half-life of three to six hours (peaking at 30 to 60 minutes) once it has been metabolized, the gap goes away.2 Additionally, there are large variations in the range of osmol gaps depending on the equation used to calculate osmolarity and the fact that some people naturally have negative osmol gaps. Because of this large range of values, small osmol gaps cannot be used to eliminate the possibility of toxic alcohol ingestion.3,4