Bench-to-bedside review: A brief history of clinical acid–base

The history of assessing the acid–base equilibrium and associated disorders is intertwined with the evolution of the definition of an acid. In the 1950s clinical chemists combined the Henderson–Hasselbalch equation and the Bronsted–Lowry definition of an acid to produce the current bicarbonate ion-centred approach to metabolic acid–base disorders. Stewart repackaged pre-1950 ideas of acid–base in the late 1970s, including the Van Slyke definition of an acid. Stewart also used laws of physical chemistry to produce a new acid–base approach. This approach, using the strong ion difference (particularly the sodium chloride difference) and the concentration of weak acids (particularly albumin), pushes bicarbonate into a minor role as an acid–base indicator rather than as an important mechanism. The Stewart approach may offer new insights into acid–base disorders and therapies.