Toxic Alcohols

-Alcohols that are metabolized to organic acids – methanol, ethylene glycol, diethylene glycol

-Even a mouthful in a child can be a toxic ingestion

Methanol: Windshield washer, printer/copier fluid, paint thinner, sterno fuel, fuel for RC cars, perfumes, “denatured” alcohol

  • Metabolized formaldehyde>formic acid – acidosis and retina/optic nerve damage
  • Intoxicated + blurry/snowfield vision ->mitochondrial poison ->seizure, coma, death
  • Can have significant level without clinical signs of intoxication
  • Can cause a false positive breath ethanol – should get blood ethanol if concern
  • Putamenal and basal ganglia hyperintensity on HCT

Ethylene glycol: Antifreeze/engine coolant

  • Glycolic acid>oxalate crystals – acidosis and renal/CNS damage
  • Hypocalcemia d/t precipitation w/ oxalate

Diethylene glycol: Brake fluid/wheel cleanter

  • Diglycolic acid
  • Less well understood, causes renal, hepatic, CNS injury

Isopropyl alcohol: Rubbing alcohol

  • Not actual toxic alcohol
  • Ketosis w/o acidosis

Propylene glycol: Antifreeze, Medication diluent (lorazepam, diazepam, phenobarb, phenytoin, nitroglycerin, Bactrim)

  • Metabolized to lactate
  • Usually metabolized normally but can cause AGMA in liver disease or large amounts

Presentation

-All cause intoxication

-Pattern w/ metabolism over time: absent to worsening AGMA + elevated to resolving osm gap

-Need to consider in all bad gap acidosis

-Osmolar gap – not very sensitive or specific – cannot use as a rule out test but can essentially rule in

  • Normal osm gap range is broad: -14 – +10
  • Typically quoted normal gap is <10
  • Osm gap >30 is fairly specific
  • Serum Osmolality (US) = (2 * (Na) + (BUN / 2.8) + (glucose / 18) + (ethanol/4.6)
    • Need to use mg/dl for BUN, glucose and ethanol – e.g. 0.08 instead of 80 for ethanol
  • Serial chems and osm gap calculations can help clarify – e.g worsening AGMA with decreasing osm gap

-Send toxic alcohol levels if concerned – turnaround dependent on location

-Substantial limitations to checking for urine CaOx crystals or florescence as adjunctive tests – neither or sensitive or specific

Treatment

Treatment threshold > 20 mg/dl regardless of symptoms

-If ethanol ≥ 0.1  mg/dl then will be preferentially metabolized before toxic alcohol and there is there is some time before needing to start treatment

Metabolic treatment:

  • Fomepizole – load then q 12h dosing while in treatment range (expensive)
  • Ethanol – target > 0.1 mg/dl
    • Loading dose 600-800 mg/kg
    • Then maintenance drip
  • Doesn’t fix acidosis or damage from metabolites that are already present

Dialysis – all are dialyzable

  • Some recommend empiric dialysis at levels > 50 mg/dl
  • Absolute: Cardiac arrest, renal failure, severe acidosis
  • Relative: Level >50, vision changes, mild acidosis, very high levels
  • May also be cheaper/safer/better than prolonged MICU admission for standard tx of overdose w/ high levels

Adjunctive treatment:

  • Methanol: Folic acid (protects optic nerve, important), NaHCO3 (shunts formic acid, not good data, more theoretical benefit)
  • Ethylene glycol: Thiamine, Pyridoxine, Magnesium (Encourage alternate metabolic pathways)