Methanol Toxicity
OVERVIEW
- industrial solvent and synthetic precursor
- highly variable lethal dose
- in itself if is not very toxic, however metabolised to formaldehyde -> formic acid (neurotoxic – retina and optic nerves)
CLINICAL FEATURES
- drunk: windshield fluid, antifreeze, paint, paint removers, gasoline, adhesives, glass cleaner, a solvent/cleaner.
- symptoms develop 12-24 hours post ingestion
- neurology: cerebral oedema, seizures, meningeal irritation, cerebral infarction, blurred vision -> blindness, scotomata, papilloedema, loss of light reflexes
- respiratory failure
- circulatory shock
- GI symptoms
INVESTIGATIONS
- raised osmolar gap
- severe metabolic acidosis (raised anion gap)
- methanol level (not useful acutely due to availability and turn around times)
- normal ionized Ca2+
MANAGEMENT
decreased production of toxic metabolites:
- -> ethanol (competitive inhibitor to alcohol dehydrogenase)
- -> 4-methylapyrazole (same as ethanol but easier to titrate and no sedative effects)
- -> sodium bicarbonate (undissociated formic acid more toxic than the dissociated product – give if pH < 7.3)
- -> folinic acid: 50mg Q4hrly (decreases formate levels and decreases toxicity)
increase elimination:
- -> haemodialysis: effectively and rapidly removed including toxic metabolites
References and Links
- CCC – Toxic Alcohol Ingestion
- CCC – Ethylene glycol toxicity
- Tox Conundrum – Ethylene glycol inebriation
Critical Care
Compendium
Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also a Clinical Adjunct Associate Professor at Monash University. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.
After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.
He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE. He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of litfl.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.
His one great achievement is being the father of three amazing children.
On Twitter, he is @precordialthump.
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