Methanol and ethylene glycol poisoning - NYSORA | NYSORA

Methanol and ethylene glycol poisoning

Learning objectives

  • Diagnose and treat intoxication with the toxic alcohols methanol and ethylene glycol (EG)

Background

  • EG is a common component of antifreeze and de-icing solutions
  • Methanol is present as a solvent in many household products, such as antifreeze, cleaning solutions, dyes, and paint removers
  • Onset of symptoms of methanol poisoning can range from 40 minutes to 72 hours, depending on the dose and co-ingestion of ethanol

Pathophysiology

  • Toxicity of methanol and EG is related to the production of toxic metabolites by the hepatic enzyme alcohol dehydrogenase (ADH)

ethylene glycol, methanol, glycolaldehyde, glycolic acid, glyoxylic acid, oxalic acid, calcium oxalate, formaldehyde, formic acid, ADH, ethanol, Fomepizole

  • Oxalic acid
    • The main toxic metabolite of EG 
    • Binds to calcium, forming insoluble calcium oxalate crystals, this can cause hypocalcemia and crystal deposition in several organs causing organ dysfunction 
  • Formic acid
    • The main toxic metabolite of methanol
    • Directly toxic to the retina which can cause visual disturbances and even blindness
    • Inhibits the mitochondrial cytochrome oxidase, which deranges ATP synthesis 

Signs and symptoms

 Ethylene glycolMethanol
Early Confusion
Stupor
Nausea
Vomiting
Mild euphoria
Drunkenness
Headache
Lethargy
Confusion
ProgressionMetabolic acidosis
Küssmaul breathing
Hypocalcemia
Hyperreflexia
Vision abnormalities
Extrapyramidal symptoms (in severe intoxication)
Seizures
Metabolic acidosis
Küssmaul breathing
Late Coma
Acute renal failure (earlier in severe intoxication)
Cardiovascular shock
Multi organ failure
Death
Blindness
Coma
Cardiovascular shock
Respiratory failure
Sudden respiratory arrest
Death

Management

  • Decreased consciousness 
    • Requires endotracheal intubation if airway is at risk
    • Administer a pre-intubation bolus of 1-2 mmol/kg sodium bicarbonate to avoid exacerbating acidosis, which will worsen symptoms
  • Supportive care
    • IV fluids
    • Vasopressors as needed
    • Correct acidemia (pH<7.3) by administering sodium bicarbonate
    • Supplement calcium in EG intoxication
  • Decontamination
    • Activated charcoal and gastric lavage have no place in the treatment of toxic alcohol intoxication
  • Seizures
    • Treat with a benzodiazepine
  • Antidotal therapy:

ethylene glycol, methanol, andidotal, ethanol, fomepizole, ADH, osmolal gap, ph, bicarbonate, oxalate crystalluria, hemodialysis,

  • Hemodialysis 
    • Start hemodialysis if
      • Methanol/EG intoxication with: Coma, convulsions, renal failure, metabolic acidosis pH<7.15, persisting acidosis despite treatment or serum anion gap>24 mmol/L
      • Plasma concentration ≥500 mg/L if not yet antidotal treatment, ≥600 mg/L if ethanol, ≥700 mg/L if fomepizole

Suggested reading

  • Rietjens SJ at al. Ethylene glycol or methanol intoxication: which antidote should be used, fomepizole or ethanol? Neth J Med. 2014 Feb;72(2):73-9. PMID: 24659589
  • Grouls R. et al. Toxicologie behandel informatie: Methanol, 2022, accessed 25/01/2023 https://toxicologie.org/methanol

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