From the Guidelines
Yes, both ethylene glycol and isopropyl alcohol can cause an anion gap metabolic acidosis, though through different mechanisms. Ethylene glycol, commonly found in antifreeze, is metabolized to glycolic acid and oxalic acid, which directly contribute to a high anion gap metabolic acidosis, as seen in the study by 1. This poisoning is particularly dangerous as it can lead to renal failure due to calcium oxalate crystal formation in the kidneys. Isopropyl alcohol (rubbing alcohol) primarily causes ketoacidosis rather than direct acid production. When metabolized, isopropyl alcohol converts to acetone, which contributes to an elevated anion gap. However, isopropyl alcohol poisoning typically produces a less severe acidosis than ethylene glycol.
Key Points to Consider
- Both ethylene glycol and isopropyl alcohol poisoning require prompt medical attention, with ethylene glycol poisoning often requiring fomepizole or ethanol therapy to block alcohol dehydrogenase, preventing the formation of toxic metabolites, as recommended by 1.
- Hemodialysis may be necessary in severe cases of either poisoning to remove the parent compound and its metabolites, with the decision to initiate extracorporeal treatment (ECTR) guided by factors such as the ethylene glycol concentration, osmol gap, and clinical indications like coma, seizures, or acute kidney injury, as outlined in the study by 1.
- The choice of ECTR modality, such as intermittent hemodialysis or continuous kidney replacement therapy, depends on availability and the patient's specific needs, with intermittent hemodialysis generally recommended over other types of ECTR when available, as suggested by 1.
Clinical Decision Making
In clinical practice, the management of ethylene glycol and isopropyl alcohol poisoning involves careful consideration of the severity of the poisoning, the presence of metabolic acidosis, and the need for antidote therapy and ECTR. The decision to initiate ECTR should be based on the most recent and highest quality evidence, taking into account the patient's individual circumstances and the potential risks and benefits of treatment, as emphasized by 1.
From the Research
Ethylene Glycol and Isopropyl Alcohol Toxicity
- Ethylene glycol poisoning classically presents as a metabolic acidosis with an increased anion gap, due to its metabolism to organic acids and increased production of lactate 2.
- However, there have been cases reported where ethylene glycol toxicity presented with a non-anion gap metabolic acidosis, without known associated confounding factors 3.
- In some cases, the ingestion of ethanol can inhibit the hepatic metabolism of ethylene glycol to organic acids, obscuring the diagnosis and presenting with a normal anion gap 2.
- Isopropyl alcohol toxicity is also associated with metabolic acidosis, but the type of acidosis (anion gap or non-anion gap) is not consistently reported in the literature.
- The diagnosis of toxic alcohol poisoning, including ethylene glycol and isopropyl alcohol, relies on the presence of an anion gap metabolic acidosis and an osmolal gap between the calculated and measured osmolality 4, 5, 6.
- However, normal anion and osmolal gaps should not rule out earlier toxic alcohol poisoning, as seen in cases of simultaneous ethanol and methanol ingestion 4.
Key Findings
- Ethylene glycol toxicity can present with both anion gap and non-anion gap metabolic acidosis 2, 3.
- The presence of an anion gap metabolic acidosis is an important clue to the diagnosis of toxic alcohol poisoning, but its absence does not rule out the diagnosis 4, 5, 6.
- The osmolal gap can be a useful marker for toxic alcohol poisoning, even in the absence of anion gap metabolic acidosis 2, 4.