TOXCARD: TOXIC ALCOHOL POISONING

Author: Kristin E. Fontes, MD (Emergency Physician, Santa Barbara Cottage Hospital and Goleta Valley Cottage Hospital) // Edited by: Cynthia Santos, MD (Senior Medical Toxicology Fellow, Emory University School of Medicine), Alex Koyfman, MD (@EMHighAK, EM Attending Physician, UTSW / Parkland Memorial Hospital), and Brit Long, MD (@long_brit, EM Attending Physician, San Antonio Military Medical Center)

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Case presentation:

A 28-year-old female is brought to the emergency department by ambulance from home after her roommate found her disoriented and poorly responsive. The roommate reports finding a small container of antifreeze in the patient’s bedroom. Vital signs are as follows: T 37.0C, HR 65, BP 126/76, RR 32, and SpO2 98% on room air.  Venous blood gas shows pH 6.97, pCO2 21, pO2 38, HCO3 4.8, and lactate 6.75.

Question:

What are the laboratory abnormalities that can occur with toxic alcohol poisoning and how can it be treated?

Pearl:

Common features of toxic alcohol poisoning are elevated anion gap metabolic acidosis and elevated osmolar gap (the latter being a distinguishing feature from ethanol poisoning); osmolar gap usually elevated early after ingestion.(1,2)

Recall the toxic alcohol metabolites and their effects:

toxic alcohol metabolism

  • EG toxicity can cause significant renal failure due to oxalate crystal deposition in the kidneys and glycolic acid, which is directly nephrotoxic; hypocalcemia and tetany can also result due to oxalate binding to calcium.(1)
  • MeOH toxicity classically causes visual disturbances (“snowfield” vision) due to formic acid-induced optic neuropathy.(1)
  • Isopropanol toxicity causes ketosis without acidosis (no lactic acid formed!).  Usually benign clinical course but can occasionally cause hemorrhagic gastritis. Fomepizole and HD not usually indicated.(1)
  • Propylene glycol toxicity often due to intravenous medication preparations containing this alcohol (e.g., diazepam, lorazepam, esmolol, nitroglycerin, phenobarbital, phenytoin) can result in severe lactic acidosis.(1)
Treatment Approach:
  • Fomepizole competitively inhibits alcohol dehydrogenase, which is involved in the metabolism of all alcohols, including ethanol. It is given to prevent the buildup of toxic metabolites from ethylene glycol (glycolic acid, glyoxylic acid, and oxalic acid) and methanol (formic acid) whose deposition in tissues can cause irreparable damage.(1)
  • Fomepizole is indicated for MeOH or EG ingestion resulting in a metabolic acidosis with an elevated osmolar gap (not accounted for by ethanol) and a serum MeOH or EG level of at least 20 mg/dL.(1)
  • Fomepizole dosing: 1) Load: 15 mg/kg (max 1.5 g) IV, diluted in 100 mL of normal saline or 5% dextrose, infused over 30 minutes; 2) Maintenance: 10 mg/kg IV every 12 hours for 4 doses, then increase to 15 mg/kg until serum toxic alcohol level is less than 20 mg/dL.(1,3)
  • Hemodialysis is indicated for toxic alcohol poisoning with an elevated osmolar gap and/or severe metabolic acidosis refractory to standard therapy, refractory hypotension, or end organ damage (i.e. acute renal failure).(1,3)
  • Vitamin Supplementation: Give folic or folinic acid to patients with MeOH toxicity to divert metabolism away from formic acid to carbon dioxide and water. Give folic acid, pyridoxine, and thiamine to patients with EG toxicity to divert metabolism to nontoxic metabolites.(1,3)
Main points:

Consider toxic alcohol poisoning in a patient with an unexplained elevated anion gap metabolic acidosis and elevated osmolar gap. Consider fomepizole and/or HD in patients with severe toxic alcohol poisoning, especially if refractory to standard therapy.

 

References:
  1. Olson KR & California Poison Control System. (2012). Poisoning & drug overdose. New York: Lange Medical Books/McGraw-Hill.
  2. Emmett M and Palmer BF. Serum osmolal gap. In: UpToDate, Forman JP (Ed), UpToDate, Waltham, MA, 2016.
  3. LeBlanc C, Murphy N. Should I stay or should I go?: toxic alcohol case in the emergency department. Can Fam Physician 2009 Jan;55(1):46-9.

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