The commonly available toxic alcohols include ethylene glycol, methanol, and isopropanol. Ethylene glycol is a sweet-tasting liquid commonly found in antifreeze, as well as in brake fluid. Methanol is used in lock deicers, windshield wiper fluid, and industrial solvents. Isopropanol is commonly marketed as “rubbing” alcohol, although it is also found in nonstreaking glass and window cleaners, soaps, cosmetics, and antifreezes.
The parent toxic alcohols cause intoxication but are not otherwise toxic to end organs. Sequential metabolism via alcohol dehydrogenase and aldehyde dehydrogenase produces the organic acids responsible for end-organ toxicity and metabolic acidosis. Ethylene glycol is metabolized to glycolic and oxalic acids; the former is responsible for the acidosis, while the latter is responsible for calcium oxalate deposition in the renal tubules and delayed acute renal failure (24-72 hours after ingestion). Hypocalcemia may occur with severe intoxication. Methanol is less intoxicating than ethanol. Methanol is metabolized to formic acid, which is responsible for both acidosis and direct retinal toxicity. Patients often report blurred or dim vision (“snowstorm”) prior to development of objective signs, including optic disc hyperemia, pupillary dilation, and poor accommodation. Pancreatitis and delayed basal ganglia lesions may occur. Isopropanol metabolism is limited to ketone formation and does not result in significant acidosis.
Antifreeze. Addition of fluorescein to antifreeze gives colorless ethylene glycol its green appearance. (Photo contributor: Matthew D. Sztajnkrycer, MD, PhD.)
Management and Disposition
For ethylene glycol and methanol, emergency management is directed toward supportive care, diagnosis of the agent, and prevention of further metabolism. Methanol, ethylene glycol, and isopropanol levels may not be readily available. However, care should be taken in interpreting ancillary data, such as urinary fluorescence and the osmolar gap. Both ethanol and fomepizole competitively inhibit alcohol dehydrogenase. Both of these reduce metabolism of the parent compound but do not enhance elimination of the toxic metabolites. Administration of folate (methanol) or pyridoxine and thiamine (ethylene glycol) may inhibit organic acid production or increase degradation by shunting metabolism to alternate pathways. Hemodialysis is indicated for signs of end-organ toxicity (eg, anion gap acidosis, renal failure, mental status changes) and should be considered for elevated toxic alcohol levels. Isopropanol ingestions require primarily supportive care.
Antifreeze Fluorescence. Application of a black light to antifreeze will demonstrate the fluorescence in body fluids, provided fluorescein has been added. This sample was obtained from the emesis of an overdose patient. (Photo contributor: Matthew D. Sztajnkrycer, MD, PhD.)
Urine Fluorescence. Under black light, the urine of this ethylene glycol overdose patient shows a bright fluorescence. (Photo contributor: Matthew D. Sztajnkrycer, MD, PhD.)