II. Labs: Excess Anion Gap
- Calculation: Excess Anion Gap (EAG)
- EAG = Anion Gap - 12 meq/L + serum bicarbonate
- Interpretation
- EAG > 30 mEq/L: Metabolic Alkalosis present
- EAG < 23 mEq/L: Non-Anion Gap Metabolic Acidosis
III. Labs: Delta Gap (Bicarbonate Gap)
- Calculation: Delta Gap (dG)
- dG = dAG/dBicarb
- Where delta Anion Gap (dAG) = AG - 12 mEq/L
- Where delta bicarb (dBicarb) = Bicarb - 24 mEq/L
- Interpretation
- dG 1 to 2
- dG <1 (negative Bicarbonate Gap)
- Non-Anion Gap Metabolic Acidosis
- Other process responsible for decreased bicarbonate
- dG >2 (positive Bicarbonate Gap)
- Metabolic Alkalosis is contributing to the acid base status
- Further interpretation: dG + bicarbonate
- dG + bicarbonate >24 mEq/L: Associated Metabolic Alkalosis
- dG + bicarbonate <24 mEq/L: Non-Anion Gap Metabolic Acidosis
IV. Labs: Gap-Gap Analysis
- Gap-Gap = Change in bicarbonate - Change in Anion Gap
- Interpretation
- Simple Anion Gap Metabolic Acidosis (Gap-Gap = -6 to 6)
- Change in Anion Gap is equivalent to the change in bicarbonate
- Superimposed Non-Anion Gap Metabolic Acidosis (Gap-Gap <-6)
- Change in bicarbonate is greater than the change in Anion Gap
- Superimposed Metabolic Alkalosis (Gap-Gap >6)
- Change in bicarbonate is less than the change in Anion Gap
- Simple Anion Gap Metabolic Acidosis (Gap-Gap = -6 to 6)
V. References
- Yavorsky and Glauser (2023) Crit Dec Emerg Med 37(9): 24-9
