A 22-year-old with type 1 diabetes presents with vomiting and altered consciousness. Blood gas: pH 7.10, PaCO2 18 mmHg, HCO3- 5 mEq/L, Na+ 138, Cl- 100, K+ 5.2 mEq/L. The anion gap is:
- A 15 mEq/L — normal
- B 22 mEq/L — mildly elevated
- C 33 mEq/L — high anion gap metabolic acidosis ✓
- D 10 mEq/L — normal
Correct answer: C. 33 mEq/L — high anion gap metabolic acidosis
Explanation
Anion gap = Na+ − (Cl- + HCO3-) = 138 − (100 + 5) = 33 mEq/L, which is a markedly elevated anion gap consistent with diabetic ketoacidosis (DKA). The respiratory compensation is appropriate (expected PaCO2 = 1.5 × HCO3- + 8 ± 2 = 1.5×5 + 8 = 15.5, actual 18 is close). High anion gap acidosis in this context reflects accumulation of beta-hydroxybutyrate and acetoacetate.
Reference: Harper's Illustrated Biochemistry, 32nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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