Understanding acid–base balance

Abstract 

Traditionally, the Hendersen–Hasselbalch model has been used to analyse clinical acid–base problems. Simplistically, this approach defines pH as a function of carbon dioxide and bicarbonate concentrations in aqueous solutions. The definition of the metabolic component of an acid–base relationship with this approach is, however, limited as bicarbonate varies with the concentration of dissolved carbon dioxide. These limitations are partly overcome by use of the base excess or anion gap. Stewart's physiochemical theory of acid–base has been used further to describe acid–base balance in the context of abnormalities in electrolytes or albumin. This review focuses on some of the limitations and practical uses of these approaches in the interpretation of metabolic acid–base disorders.

Keywords:  metabolic acidosis, base excess, anion gap, hyperchloraemia, strong ion gap