A Rare Case of Elevated Osmolar Gap in Diabetic Ketoacidosis/Hyperosmolar Hyperglycaemic State in the Absence of Concomitant Toxic Alcohol Ingestion

Abstract

The serum osmolar gap, defined as the difference between measured osmolality and calculated osmolarity, is a convenient method to screen for toxins in serum. In normal circumstances, the difference between the two is 6–10 mol/kg. Typical contributors to serum osmolarity are sodium bicarbonate, sodium chloride, glucose and urea. An elevated gap, defined as a difference >10 mol/kg, can occur if a sufficient quantity of an additional solute other than those mentioned above is present in the serum or there are inaccuracies in sodium measurement secondary to hyperlipidaemia and hyperproteinaemia. An elevated serum osmolar gap should thus prompt clinicians to check for toxic alcohol levels. Treatment with fomepizole should not be delayed if suspicion is high. Isolated diabetic ketoacidosis can occasionally present with an elevated osmolar gap in the absence of concomitant alcohol ingestion. This finding is attributed to the production of acetone and glycerol. We describe the case of a 62-year-old man presenting with diabetic ketoacidosis/hyperosmolar hyperglycaemic state and an elevated osmolar gap in the absence of toxic alcohol ingestion.

Mind the gap: Measured and Calculated Osmolarity are Not Interchangeable in Diabetic Hyperglycemic Emergencies

“…The reasons for the elevation of the osmolar gap in DKA have been explored in previous publications and are likely multifactorial. The osmolar gap can represent the presence of osmotically active substances other than glucose, sodium and urea [6], which occurs in DKA through the production of non-ionized ketone bodies, predominantly acetone [5,21]. The discrepancy between measured and calculated values may also be due to aberrant sodium levels obtained using indirect potentiometric methods in the context of severe dehydration and reduced plasma water fraction [8].…”