The Δanion gap/ΔHCO3 ratio in patients with a high anion gap metabolic acidosis
- Michael Emmett, MD
Michael Emmett, MD
- Editor-in-Chief — Nephrology
- Section Editor — Fluid and Electrolytes
- Chief of Internal Medicine
- Baylor University Medical Center
NORMAL SERUM ANION GAP
Determination of the serum anion gap (AG) is an important step in approaching the differential diagnosis of metabolic acidosis [1-5]. (See "Approach to the adult with metabolic acidosis", section on 'Physiologic interpretation of the serum anion gap'.)
The serum AG is calculated from the following formula, which represents the difference between the primary measured cation (Na) and the primary measured anions (Cl and HCO3):
Serum AG = Na - (Cl + HCO3)
Some clinicians also include the serum potassium in the formula; when this is done, the normal range increases by about 4 meq/L:
Serum AG = (Na + K) - (Cl + HCO3)
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- NORMAL SERUM ANION GAP
- ΔAG/ΔHCO3 RATIO
- The ΔAG/ΔHCO3 in lactic acidosis
- The ΔAG/ΔHCO3 in ketoacidosis
- The ΔAG/ΔHCO3 in other causes of high anion gap acidosis
- - D-lactic acidosis and toluene inhalation
- - Chronic kidney disease
- The ΔAG/ΔHCO3 in patients with mixed metabolic disorders
- POTENTIAL SOURCES OF ERROR
- SUMMARY AND RECOMMENDATIONS