Modern quantitative acid–base chemistry

Abstract

Quantitative analysis of ionic solutions in terms of physical and chemical principles has been effectively prohibited in the past by the overwhelming amount of calculation it required, but computers have suddenly eliminated that prohibition. The result is an approach to acid-base which revolutionizes the ability to understand, predict and control what happens to H+ ions in living systems. This review outlines that approach and suggests some of its most useful implications. Quantitative understanding requires distinctions between independent variables (in body fluids: pCO2, net strong ion charge and total weak acid, usually protein), and dependent variables ([HCO3-], [HA], [A-], [CO32-], [OH-] and [H+] (or pH)). Dependent variables are determined by independent variables, and can be calculated from the defining equations for the specific system. H+ ion movements between solutions can not affect H+ ion concentration; only changes in independent variables can. Many current models for ion movements through membranes will require modification on the basis of this quantitative analysis. Whole body acid-base balance can be understood quantitatively in terms of the 3 independent variables and their physiological regulation by the lungs, kidneys, gut and liver. Quantitative analysis also shows that body fluids interact mainly by strong ion movements through the membranes separating them.