title: Practical approach to physical-chemical acid-base management. Stewart at the bedside.
abstract: The late Peter Stewart developed an approach to the analysis of acid-base disturbances in biological systems based on basic physical-chemical principles. His key argument was that the traditional carbon dioxide/bicarbonate analysis with just the use of the Henderson-Hasselbalch equation does not account for the important role in the regulation of H(+) concentration played by strong ions, weak acids and water itself. Acceptance of his analysis has been limited because it requires a complicated set of calculations to account for all the variables and it does not provide simple clinical guidance. However, the analysis can be made more pragmatic by using a series of simple equations to quantify the major processes in acid-base disturbances. These include the traditional PCO2 component and the addition of four metabolic processes, which we classify as "water-effects," "chloride-effects," "albumin effects," and "others." Six values are required for the analysis: [Na(+)], [Cl(-)], pH, Pco2, albumin concentration, and base excess. The advantage of this approach is that it gives a better understanding of the mechanisms behind acid-base abnormalities and more readily leads to clinical actions that can prevent or correct the abnormalities. We have developed a simple free mobile app that can be used to input the necessary values to use this approach at the bedside (Physical/Chemical Acid Base Calculator).
authors.affiliation: Department of Critical Care, McGill University Health Centre, Montreal, Quebec, Canada.
authors.forename: Sheldon
authors.initials: S
authors.lastname: Magder
authors.forename: Ali
authors.initials: A
authors.lastname: Emami
mesh_terms: D000136:Acid-Base Equilibrium / Q000502:physiology*; D000138:Acidosis / Q000378:metabolism*; D000471:Alkalosis / Q000378:metabolism*; D055598:Chemical Phenomena; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008954:Models, Biological
keywords: acid-base; base excess; chloride; strong ion difference