Patients with recent history of ingesting toxic amounts of methanol and having
osmolal gap of more than 10 mOsm/kg H2O were included.
This was supported by the evidence of a high plasma
osmolal gap, which is the difference between the measured plasma osmolality in the laboratory and calculated plasma osmolality.
Laboratory testing and diagnosis of methanol and ethylene glycol are based on the presence of a high anion gap metabolic acidosis, presence of a serum
osmolal gap (a difference between measured osmolality and calculated osmolality [greater than or equal to] 10), and measuring the levels of the toxic alcohols which is used for confirmation (typically these tests are not time sensitive, and treatment should not be withheld in any patient suspected of having toxic alcohol ingestion).
A 61-year-old man presented with an increased anion-gap metabolic acidosis, an increased serum
osmolal gap, and a negative result in an alcohol screen.
Urinary electrolytes and
osmolal gap may be useful in assessment of metabolic alkalosis and normal AG metabolic acidosis.
The American Academy of Toxicology recommends treatment with ethanol (or fomepizole if available) in the presence of a methanol level >20 mg/dl, a documented history of methanol ingestion with a serum
osmolal gap >10 mOsm/l or strong clinical suspicion of methanol poisoning with at least two of the following: arterial pH <7.3, serum HCO3 <20 mEq/l and
osmolal gap >20 mOsm/[l.sup.2].
Ethylene glycol poisoning with a normal anion gap caused by concurrent ethanol ingestion: Importance of the
osmolal gap. Am J Kidney Dis 1996; 27(1):130-133.
The serum
osmolal gap (75 mOsm/kg) was calculated as follows:
Osmolal gap = freezing-point depression osmometer value --(2 X [[Na.sup.+]] + [glucose]/18 + [blood urea nitrogen]/2.8 + [ethanol]/4.6), where the [Na.sup.+] concentration is in millimoles per liter and the glucose, blood urea nitrogen, and ethanol concentrations are in milligrams per deciliter.
AKA can also be associated with other laboratory abnormalities, such as increased serum lactate and an
osmolal gap, as well as reduced electrolyte concentrations.