[Diagnosis, countermeasure and classification of acidosis]

Acidosis is the result of the net addition of hydrogen ion to the extracellular space or loss of bicarbonate from that space. Hydrogen ion may be added by the increased production of strong acids, an increase in CO2 concentration, or the addition of exogenous acids. The common approach to the differential diagnosis of metabolic acidosis is to divide the patients into two categories based on whether the anion gap in plasma is increased or not. Metabolic acidosis with normal anion gap (hyperchloremic) suggests that bicarbonate has been effectively replaced by chloride. In contrast, metabolic acidosis with an increased anion gap suggests addition to the body fluids of an acid other than hydrochloric acids or its equivalent.