Peter A. StewartPeter Arthur Robert Stewart (1921–1993) was a Canadian physiologist who introduced an alternate approach to understanding acid base physiology.
He outlined his model in a paper in 1978, and explained it his 1981 book, ''How to Understand Acid-Base''. The book was unavailable for many years, then made available on-line and finally reprinted in 2009, with additional chapters on current applications in clinical medicine.
The Stewart approach models the complex chemical equilibrium system known as acid-base balance. Stewart introduced the term "strong ion difference" or [SID] to mean the concentration of strongly dissociating cations minus the concentration of strongly dissociating anions. He characterised this, the total weak acid concentration and the partial pressure of CO2 as independent variables and formulated a quartic equation relating [H+] to these three independent variables. The quartic equation was solved numerically by computer and has never been validated by titration or phsyiological experiments. The model ignores intracellular and extravascular compartments.
The impact of the Stewart analysis has been slow in coming but there has been a recent resurgence in interest, particularly as this approach provides explanations for several areas which are otherwise difficult to understand (''e.g.'', dilutional acidosis, acid-base disorders related to changes in plasma albumin concentration). Provided by Wikipedia