The correct answer is:

Methanol

Educational Objective:

Recognize the early presentation of possible methanol ingestion.

Key Point:

The child likely drank windshield washer fluid that contained methanol. She now presents with the early findings of methanol ingestion: altered mental status in the context of an elevated osmolar gap and no anion gap.

Explanation:

This case illustrates the difference between an early presentation after an observed, accidental methanol ingestion in a child versus the typically late presentation of an adult after an intentional ingestion of methanol.

Early after methanol ingestion, the patient will present with mild signs of inebriation (varying with the dose of ingestion from nearly no to severe inebriation), GI symptoms, and an elevated osmolar gap WITHOUT acidosis or anion gap. This early hematological pattern is due to the fact that methanol itself is only osmotically active. The compound is NOT an acid.

After a latent period of normalcy (usually about 12 hours, may vary from 1 hour to 30 hours), the methanol will metabolize to its toxic metabolite formic acid (via formaldehyde), which IS an acid, but NOT osmotically active. This is the stage at which adults typically present because at this point they develop significant visual symptoms. At this later stage, the patient will present with severe acidosis, but no longer with an osmolar gap.

Between the osmolar gap of the initial methanol and the later anion gap of formic acid is a phase during which a decreasing osmolar gap and a rising anion gap will lead to a temporary phase of a double gap.

Many physicians have only memorized the late presentation of an intentional methanol ingestion (significant anion gap acidosis), which leads to missing the diagnosis in a child who presents early with an osmolar gap.

Drinking from an unlabeled bottle is a common pediatric route of exposure. Parents and others commonly rebottle potentially dangerous solutions into unmarked containers that are easily opened by a child. Many potentially toxic alcohols look like fluids that may appeal to a child (e.g., a young child may mistake the blue-colored liquid for a sports drink).

Other common sources of methanol available around the home (some with high concentrations of methanol) include carburetor cleaning fluids, model engine fuels, cooking fuel, shellacs, lacquers, adhesives, and inks.

It helps to be aware that ethylene glycol is typically green in color because of the addition of fluorescein to aid mechanics in the detection of leaks. Isopropyl alcohol and propylene glycol are both clear. Ethanol is only typically blue in color in windshield wiper fluid; otherwise it is usually clear.