Interpreting delta ratio in mixed acid-base disorders: a delta-delta ratio less than 1 suggests what?

Interpreting delta ratio in mixed acid-base disorders: a delta-delta ratio less than 1 suggests what?

• A. Concurrent metabolic alkalosis
• B. Concurrent non-anion gap metabolic acidosis
• C. Pure high anion gap metabolic acidosis
• D. Normal anion gap metabolic acidosis

Answer: (B)

Interpreting the delta ratio hinges on comparing how much the anion gap (AG) has risen to how much the bicarbonate (HCO3) has fallen in a high AG metabolic acidosis. Normal values are about an AG of 12 and HCO3 of 24. Calculate ΔAG = measured AG − 12 and ΔHCO3 = 24 − measured HCO3. The delta ratio = ΔAG / ΔHCO3. If this ratio is around 1, the bicarbonate loss matches the AG rise, suggesting a single high anion gap metabolic acidosis. If the ratio is less than 1, bicarbonate has fallen more than the AG has risen, indicating an additional non-anion gap (hyperchloremic) metabolic acidosis is present along with the high AG acidosis. Therefore, a delta ratio less than 1 points to concurrent non-anion gap metabolic acidosis.

Interpreting the delta ratio hinges on comparing how much the anion gap (AG) has risen to how much the bicarbonate (HCO3) has fallen in a high AG metabolic acidosis. Normal values are about an AG of 12 and HCO3 of 24. Calculate ΔAG = measured AG − 12 and ΔHCO3 = 24 − measured HCO3. The delta ratio = ΔAG / ΔHCO3.

If this ratio is around 1, the bicarbonate loss matches the AG rise, suggesting a single high anion gap metabolic acidosis. If the ratio is less than 1, bicarbonate has fallen more than the AG has risen, indicating an additional non-anion gap (hyperchloremic) metabolic acidosis is present along with the high AG acidosis. Therefore, a delta ratio less than 1 points to concurrent non-anion gap metabolic acidosis.