Use of the DeltaAG/DeltaHCO3- ratio in the diagnosis of mixed acid-base disorders.

When a strong acid is added to plasma, one expects a quantitative relationship between excess anion gap (DeltaAG) and bicarbonate deficit (DeltaHCO(3)(-)) with the DeltaAG/DeltaHCO(3)(-) ratio close to unity. If true, then this ratio could be used to diagnose mixed acid-base disorders in patients with metabolic acidosis. Although the mean ratio in selected patients is close to unity, this ratio also has a wide range, making its use in individual patients problematic. The ratio should therefore be used cautiously in making a diagnosis of mixed acid-base disorders.