Toxic Alcohols:

-Calculate the Osmol gap:

 Calculated osm = (2xNa) + (Glucose/18) + (BUN/2.8) + (EtOH/4.6) + (ammonia/1.7)

-It is neither sensitive, nor specific!
-The “normal” range for the osmol gap of a healthy individual has a large range (from -14 to 16!)
- Without knowing a patient’s baseline, a value that appears within “normal” range may actually be elevated.
-Ethanol and ammonia must be included in the calculation!
-The parent compound (methanol, ethylene glycol) contributes to an osmol gap, whereas the metabolites (formic acid, glycolic acid) contribute to an anion gap.
- An osmol gap may only be present in the initial stages of intoxication, and has a reciprocal relationship with the anion gap
-Other substances can contribute to the osmol gap and make it seem falsely elevated, substances include: sorbitol, IV dye (for CT scan), mannitol and diuretics, glycerin
-An isolated level may not be helpful unless it is very high

Methanol:
-Where found: Brake fluid, cologne/perfume, windshield washer fluid, solid cooking fuel, solvents
-Metabolism: Methanol to Formaldehyde to Formic acid to CO2 and H2O
-Effects: lactic acidosis, blindness from damage/edema of optic disc (may not be symmetric!), basal ganglia necrosis/hemorrhage, acute kidney injury, pancreatitis
-Treatment:  Fomepizole and prompt dialysis, +/- Alkalinization

*Additional facts: Hyperglycemia (>140) is associated with increased mortality, and it will trigger a positive level on a breathalyzer

Ethylene Glycol:
-Where found:  Antifreeze, air conditioning units
-Metabolism: Ethylene Glycol to Glycoaldehyde to Glycolic Acid to Glyoxylic acid to oxalic acid to Calcium oxalate
-Effects: Renal toxicity, cerebral edema, cranial nerve palsies, hypocalcemia from crystal deposition and subsequent seizure or arrhythmia
-Treatment: Fomepizole alone is sufficient if patient is minimally symptomatic! Initiate dialysis if patient has metabolic acidosis, acute kidney injury, seizures or coma

*Additional facts: calcium oxalate crystals in the urine are neither sensitive nor specific for diagnosis

Isopropanol (Isopropyl Alcohol):
-Where found: Rubbing alcohol, cosmetics, nail polish remover
-Metabolism:  Isopropanol to Acetone
-Effects: Ketosis without acidosis! GI irritation, progressing to GI hemorrhage in more severe cases.  Rarely, profound hypotension
-Treatment: fomepizole, symptomatic/supportive care

*Additional facts: Acetone can cause a falsely elevated creatinine due to lab interference

References:

-Hoffman, Robert, Howland, Mary Ann, Lewin, Neal,Nelson, Lewis, Goldfrank, Lewis, Flomenbaum, Neal E. Goldfrank’s Toxicologic Emergencies, 10th Edition.  New York: McGraw-Hill Education; 2015. Print.

-Sharma AN, O'Shaughnessy PM, Hoffman RS, Casavant MJ, Shah MN, Battels R. Urine Fluorescence: Is It a Good Test for Ethylene Glycol Ingestion? Pediatrics. 2002;109(2):345–5. 

-Fogazzi GB. Crystalluria: a neglected aspect of urinary sediment analysis. Nephrol Dial Transplant. 1996 Feb;11(2):379–87. 

-Wallace KL, Suchard JR, Curry SC, Reagan C. Diagnostic use of physicians' detection of urine fluorescence in a simulated ingestion of sodium fluorescein-containing antifreeze. Ann Emerg Med. 2001 Jul;38(1):49–54. 

-McStay CM, Gordon PE. Images in clinical medicine. Urine fluorescence in ethylene glycol poisoning. N Engl J Med. 2007 Feb 8;356(6):611–1.