What is the treatment for ethylene glycol (antifreeze) poisoning?

Treatment for Ethylene Glycol (Antifreeze) Poisoning

The treatment for ethylene glycol poisoning requires immediate administration of fomepizole as an antidote, along with hemodialysis for severe cases with high ethylene glycol concentrations (>50 mg/dL), significant metabolic acidosis, or renal failure.

Diagnosis and Initial Assessment

• Suspect ethylene glycol poisoning based on:

  • History of antifreeze ingestion
  • Elevated anion gap metabolic acidosis
  • Elevated osmolar gap
  • Presence of calcium oxalate crystals in urine
  • Visual disturbances
  • Neurological symptoms (inebriation, ataxia, coma, seizures)

• Laboratory tests to obtain:

  • Serum ethylene glycol levels
  • Arterial blood gas
  • Electrolytes (to calculate anion gap)
  • Osmolality (to calculate osmolar gap)
  • Renal function tests
  • Urinalysis (for oxalate crystals)

Treatment Algorithm

1. Antidote Administration

• Fomepizole (preferred antidote) 1:

  • Loading dose: 15 mg/kg IV (administered over 30 minutes)
  • Maintenance: 10 mg/kg every 12 hours for 4 doses
  • Then: 15 mg/kg every 12 hours until ethylene glycol levels are <20 mg/dL
  • Note: Do not use polycarbonate syringes or needles when administering fomepizole

• Ethanol (alternative if fomepizole unavailable):

  • Loading dose to achieve blood level of 100-150 mg/dL
  • Maintenance infusion to maintain this level

2. Extracorporeal Treatment (ECTR) 2

Indications for hemodialysis:

• When fomepizole is used:

  • Ethylene glycol concentration >50 mmol/L (>310 mg/dL)
  • Osmol gap >50
  • Glycolate concentration >12 mmol/L
  • Anion gap >27 mmol/L
  • Severe clinical features (coma, seizures, or AKI)

• When ethanol is used:

  • Ethylene glycol concentration >20 mmol/L (>124 mg/dL)
  • Osmol gap >20
  • Same criteria for glycolate, anion gap, and clinical features as above

• When no antidote is available:

  • Ethylene glycol concentration >10 mmol/L (>62 mg/dL)
  • Osmol gap >10
  • Same criteria for glycolate, anion gap, and clinical features as above

3. Supportive Therapy

• Correct metabolic acidosis with sodium bicarbonate
• Administer thiamine (100 mg IV) and pyridoxine (50 mg IV) to promote metabolism away from toxic metabolites 3
• Maintain fluid balance and electrolyte correction
• Monitor calcium levels and supplement if hypocalcemia develops
• Provide respiratory support as needed

4. Dosing Adjustments During Hemodialysis 1

• Increase fomepizole dosing frequency to every 4 hours during hemodialysis
• After hemodialysis completion:
  • If <1 hour since last dose: Do not administer dose
  • If 1-3 hours since last dose: Administer 1/2 of next scheduled dose
  • If >3 hours since last dose: Administer next scheduled dose

5. Treatment Discontinuation

• Continue treatment until:
  • Ethylene glycol levels are undetectable or <20 mg/dL
  • Patient is asymptomatic with normal pH
  • Resolution of metabolic acidosis

Important Considerations and Pitfalls

• Do not delay treatment while waiting for ethylene glycol levels; begin treatment based on clinical suspicion and presence of metabolic acidosis 1
• Activated charcoal is ineffective for ethylene glycol poisoning 4
• The toxic effects of ethylene glycol come primarily from its metabolites (glycolic acid and oxalic acid), not the parent compound 2
• Patients may initially present with symptoms resembling alcohol intoxication before developing severe metabolic acidosis 5
• Calcium oxalate crystal formation can cause renal damage; monitor renal function closely 6
• Intermittent hemodialysis is preferred over continuous kidney replacement therapy when available 2
• Cessation of ECTR is recommended once the anion gap is <18 mmol/L or ethylene glycol concentration is <4 mmol/L 2

Early recognition and aggressive treatment are essential to prevent progression to severe metabolic acidosis, renal failure, and death in ethylene glycol poisoning.