23 year old Type 1 Diabetic in the Emergency Department

A 23-year-old type 1 diabetic is brought to the emergency department after being found in a coma. The scent of acetone is present on the patient’s breath. Urinary catheterization with subsequent dipstick analysis demonstrates marked positivity for glucose and ketones. Stat blood chemistries would most likely show which of the following values for the anion gap?

  1. 6 mEq/L
  2. 11 mEq/L
  3. 13 mEq/L
  4. 15 mEq/L
  5. 20 mEq/L

The correct answer is 5. 20 mEq/L.

The patient is in diabetic ketoacidosis, as indicated by the acetone scent to the breath and the glucose and ketones in the urine. Diabetic ketoacidosis produces an increased anion gap, since the anion for the acid that is produced (acetoacetate) is not one of the usually measured ions. The anion gap is usually estimated by subtracting the sum of the Cl- and HCO3- concentrations from the plasma Na+ concentration; the normal value for the anion gap is 12 ± 4 mEq/L. Causes of increased anion gap include conditions that produce ketoacidosis (diabetes mellitus, alcoholism, starvation), renal failure with retained sulfate and phosphate, drugs or metabolites (salicylate or ethylene glycol poisoning), alkalosis with increased negative charge of protein anions, and dehydration (hemoconcentration).

6 mEq/L (choice 1) is below the lower limit of normal. The anion gap may be decreased because of a decrease of negatively charged serum proteins (eg, in hypoalbuminemia), an increase in proteins carrying few negative charges (eg, hypergammaglobulinemia), or an increase in unmeasured cations (e.g., magnesium, calcium, or lithium).

The other values (choice 2, 3, and 4) are within normal limits.

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Dr. Lawrence Kindo

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