Ingestion of ethylene glycol or methanol may result in life-threatening metabolic acidosis, renal failure, blindness, and dea

The Mountain ™(for suspected toxic alcohol poisoning)

In cases of suspected ethylene glycol or methanol poisoning, “The Mountain” visual schematic may clarify the dynamic relationship between theosmol gap and the anion gap and help prioritize treatment options while awaiting definitive quantitative levels (Mycyk MB, Aks SE: Amer J Emerg Med 2003;21:333-335).

Patients poisoned with a toxic alcohol often arrive in the ED without the classic findings of an anion gap acidosis in the presence of an elevated osmol gap.This may occur in two specific scenarios: (1) early after ingestion when acidosis has not yet occurred; (2) late after ingestion when most of the parent alcohol has metabolized to the toxic acids and the osmol gap is no longer elevated.It is not important to memorize every step of the metabolism of ethylene glycol or methanol as illustrated in Figure 1.It is simply important to recognize that the osmol gap, which occurs from the parent alcohol, and the anion gap, which is generated from the accumulation of acid metabolites, peak at two extremes during the time course of poisoning.Early after toxic alcohol poisoning, an elevated osmol gap and no acidosis are expected (Figure 2, point A); in patients arriving late after ingestion, a large anion gap acidosis and no significant osmol gap are expected (Figure 2, point B) because the parent alcohol has metabolized to the acid metabolites.An anion gap acidosis in the presence of an elevated osmol gap is only evident during the time interval between A and B in Figure 2 after some of the parent alcohol has metabolized to toxic acids.

Use “The Mountain” for proper interpretation of the osmol gap and anion gap. Prioritize alcohol dehydrogenase (ADH) inhibition with fomepizole (Antizol®) or an ethanol drip early in the course of poisoning (before metabolism to the toxic acids). Prioritize nephrology consultation for hemodialysis removal of the toxic acids when patients present late in the course of poisoning.

Figure 1: Metabolism of toxic alcohols

Ethylene glycol>>glycoaldehyde>>glycolate>>glyoxylate>>oxalate

ADH

Methanol>>formaldehyde>>formate

(ADH: Alcohol dehydrogenase)

Figure 2: The Mountain

OSMOLSACIDS

Time

ACB

Appropriate use of“The Mountain” simply requires an estimation of the time of ingestion (i.e early vs. late) and a quantitative serum ethanol level.If a concomitant ethanol level is >100mg/dL, metabolism to the toxic acids is delayed because of competitive ADH inhibition by ethanol.Thus, the onset of acidosis is delayed even further as demonstrated in the shifted 2^nd peak of“The Mountain” in Figure 3.

Figure 3: The Mountain in the presence of an ethanol level >100mg/dL

OSMOLSACIDS

Time

Remember, in cases of suspected toxic alcohol poisoning, a high osmol gap, even without an acidosis (Figure 2, point A), should prompt inhibition of alcohol dehydrogenase (ADH) and stat quantitative levels of ethylene glycol and methanol.Call your local poison center (800-222-1222) or toxicologist for further help in these cases.