Increased osmolal gap
in alcoholic ketoacidosis and lactic acidosis.
Classic laboratory abnormalities include hyperammonemia, presence of an osmolal gap
, hypernatremia, high anion gap metabolic acidosis, and elevated liver enzymes.
After hemodialysis was performed, the patient's postdialysis serum showed an osmolal gap
of 6 mOsm/kg and an EG concentration of 50 mg/dL (8.2 mmol/L).
* Patients with AKA will present with an increased anion gap in combination with an increased osmolal gap
. The crucial differential diagnoses for an increase in both the anion and osmotic gaps are DKA, lactic acidosis, or ingestion of methanol or ethylene glycol.
 Nonstandard abbreviations: OG, osmolal gap
; ED, emergency department; BUN, blood urea nitrogen; eGFR, estimated glomerular filtration rate.
As it happened, we were alerted to a potential problem by the unusually large negative osmolal gaps
in all 3 patients.
Background: The osmolal gap
(OG) is a screening test for the detection of toxic volatiles such as methanol and ethylene glycol.
Other surrogate markers, e.g., measurement of the serum or plasma osmolality and calculation of the osmolal gap
, have been studied as alternatives to direct assays of these alcohols (55,56).
At a given time after ingestion, the concentrations of the remaining ethylene glycol and the accumulated acidic metabolites affect the magnitude of the osmolal gap
and anion gap, respectively.