Antifreeze toxicity in pets

Ethylene glycol is metabolized by alcohol dehydrogenase into toxic metabolites, notably oxalic acid, which binds calcium to form harmful calcium oxalate crystals in the kidneys, leading to acute kidney injury (AKI) and failure. AKI symptoms include anorexia, vomiting, lethargy, increased thirst, and changes in urination. Toxic byproducts also cause severe metabolic acidosis and hypocalcemia, often with a large osmolar gap.

1. Gastrointestinal: Initial irritation causes vomiting in both cats and dogs.

2. Neurological: Hyperosmolality and cerebral edema result in mental dullness and ataxia. In late neurological phase miosis and coma can occur.

3. Metabolic: Severe metabolic acidosis arises from organic acid metabolites.

4. Cardiopulmonar: tachycardia, tachypnea, pulmonary edema, arrythmias.

5. Renal: Calcium oxalate crystals and toxic metabolites cause renal epithelial damage, leading to actus kidney failure.

Progression:

• Acute symptoms appear within 30 minutes to 12 hours - polyuria, polydipsia, vomiting, diarrhea, mental dullness, ataxia.

• After an initial recovery, severe renal failure symptoms emerge around 12–24 hours in cats and 36–72 hours in dogs. In this phase cardiopulmonary symptoma mat occur.

• By 72–96 hours, anuric renal failure often develops, with painful, enlarged kidneys on examination.

Emesis is not recommended due to rapid absorption of EG. Activated charcol is not effective.

Hemodialysis and peritoneal dialysis, though less common, are effective options for rapidly clearing ethylene glycol toxins in severe cases.

Antidote (fomepizole is preferred due to its fewer side effects)

Dogs

• Fomepizole: 20 mg/kg IV initially, then 15 mg/kg IV every 12 hours (two doses), followed by 5 mg/kg IV (one dose).

• Ethanol IV (Continuous Infusion): 1.3 mL of 30% ethanol/kg IV bolus, then 0.42 mL/kg/hour for 48 hours.

• Ethanol IV (Bolus Doses): 5.5 mL of 20% ethanol/kg IV every 4 hours for five doses, then every 6 hours for four doses.

Cats

• Fomepizole: 125 mg/kg IV initially, then 31.25 mg/kg IV every 12 hours (three doses).

• Ethanol IV (Continuous Infusion): Same as dogs, 1.3 mL of 30% ethanol/kg IV bolus, followed by 0.42 mL/kg/hour for 48 hours.

• Ethanol IV (Bolus Doses): 5 mL of 20% ethanol/kg IV every 6 hours for five doses, then every 8 hours for four doses.

Symptomatic care: correct acid–base and electrolyte derangements (mainly calcium fluconate for hypocalcemia and bicarbonate for metabolic acidosis), correct fluid imbalances, provide antiemetics.

Prognosis depends on prompt treatment, the amount ingested, and the species affected. Even with treatment, chronic and often severe renal impairment is likely.