Calculating the Anion Gap in Diabetic Ketoacidosis

Authors: 

MANJARI DEVIDI, MD, MS
SUNIL DACHA, MD
Chicago 


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Patients with diabetic ketoacidosis (DKA) frequently have hyperglycemia. Serum sodium in these patients should not be corrected for hyperglycemia to calculate the anion gap for acidosis because extracellular fluid shifts caused by hyperglycemia will dilute serum chloride and bicarbonate. If serum sodium is corrected for hyperglycemia, it will give an erroneously high anion gap and an erroneous severity of acidosis in DKA.1,2 This is an important yet not well-known fact.

References: 

1. Lippmann BJ. Fluid and electrolyte management. In: Ewald GA, Mc Kenzie CR. Manual of Medical Therapeutics. 28th ed. Boston: Little, Brown; 1995:46.
2. Tomer Y. Calculating the anion gap for patients with acidosis and hyperglycemia. Ann Intern Med. 1998;129:753.