Toxic Alcohol Poisoning

Chapter 80 Toxic Alcohol Poisoning



Aaron B. Skolnik, MD , Susan R. Wilcox, MD




1 What are the compounds commonly referred to as the toxic alcohols?


Typically, the term toxic alcohols includes isopropanol, methanol, and ethylene glycol. Ethanol, of course, may also be toxic.



2 What household or commercial products commonly contain toxic alcohols?




image Isopropanol (or isopropyl alcohol) is most commonly sold as rubbing alcohol, in a 70% solution. It can also be found in antifreezes, glass cleaners, jewelry cleaner, stain removers, deicers, household disinfectants, and hand sanitizers.


image Methanol can be found in windshield washer fluid, antifreeze, copy machine fluid, canned fuel (Sterno), and some solvents. Perhaps most famously, methanol is a frequent contaminant in illicitly distilled alcoholic beverages—hence the term moonshine blindness, originating from methanol retinal toxicity.


image Ethylene glycol is often the main ingredient in automobile antifreeze and is sometimes used as a solvent.



3 What are potentially lethal doses of isopropanol, methanol, and ethylene glycol?




image Isopropanol ingestion of 150 to 250 mL can be lethal because of central nervous system (CNS) and myocardial depression.


image The reported lethal dose of methanol is 1.2 mL/kg; however, as little as 30 mL (6 teaspoons) may cause permanent vision impairment.


image The lethal dose of ethylene glycol in untreated patients varies, but 100 mL is a common conservative approximation.



4 What are the mechanisms of toxicity for isopropanol?


Isopropanol is estimated to be twice as intoxicating by volume as ethanol. It is a CNS depressant and may cause peripheral vasodilation, myocardial depression, and subsequent shock at high doses. It is metabolized by alcohol dehydrogenase (ADH) to acetone, which appears to contribute to further CNS depression. Isopropanol is extremely irritating to the gastric mucosa and classically causes severe gastritis, which may be hemorrhagic.



5 What are the mechanisms of toxicity for methanol?


Methanol is first metabolized by ADH to formaldehyde, which is then rapidly converted to formic acid by aldehyde dehydrogenase. Formic acid inhibits mitochondrial electron transport, leading to acidemia and production of reactive species. It also depletes glutathione, which is an endogenous antioxidant. The combination of these effects leaves cells that are under significant oxidative stress such as those in the retina and putamen, exposed to oxidant cytotoxicity.



6 What are the mechanisms of toxicity for ethylene glycol?


Ethylene glycol is metabolized to toxic glycolic acid, glyoxylic acid, oxalic acid, and several other minor metabolites. Oxalic acid precipitates with calcium into calcium oxalate crystals. In addition to causing hypocalcemia, deposition of oxalate in the renal tubules and other tissues causes cell death. The resulting metabolic acidosis, renal failure, pulmonary edema, and cerebral injury contribute to mortality in these patients.



7 What are the signs and symptoms of toxic alcohol poisoning?


CNS depression is the common element in toxic alcohol poisoning, ranging from typically mild in the case of methanol to profound intoxication in the case of isopropanol or ethylene glycol poisoning. Patients who ingest any of these substances may ultimately have coma, shock, and death. Each of the toxic alcohols has key clinical features that distinguish one from the other. Isopropanol-intoxicated patients typically have prominent gastrointestinal symptoms and may present with severe abdominal pain, vomiting, or hematemesis. Because acetone is the metabolite of this alcohol, ketosis without acidosis develops, and patients have fruity breath odor.


Retinal toxicity is the hallmark of methanol poisoning and may develop many hours after ingestion. Visual complaints may vary, with complete vision loss, afferent pupillary defects, and optic disc hyperemia on funduscopic examination being late findings.


Ethylene glycol toxicity usually begins with CNS depression. Hypocalcemia may cause tetany or myoclonus. Untreated, patients may progress to seizure, pulmonary edema, and ultimately renal failure, cerebral edema, and death.

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Jul 6, 2016 | Posted by in CRITICAL CARE | Comments Off on Toxic Alcohol Poisoning

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