Clinical review: reunification of acid-base physiology

Abstract

Recent advances in acid-base physiology and in the epidemiology of acid-base disorders have refined our understanding of the basic control mechanisms that determine blood pH in health and disease. These refinements have also brought parity between the newer, quantitative and older, descriptive approaches to acid-base physiology. This review explores how the new and older approaches to acid-base physiology can be reconciled and combined to result in a powerful bedside tool. A case based tutorial is also provided.

Figure 1

The continuum of approaches to understanding acid–base physiology. All three approaches share certain affecter elements and all use markers and derived variables to describe acid–base imbalance. A_TOT, total weak acids; PCO₂, partial carbon dioxide tension; SBE, standard base excess; SID, strong ion difference; SIG, strong ion gap.

Figure 2

Carbon dioxide titration curves. Computer simulation of in vivo CO₂ titration curves for human plasma using the traditional Van Slyke equation and various levels of A_TOT (total weak acids) from normal (17.2) to 25% of normal. Also shown is the titration curve using the A_TOT corrected standard base excess (SBEc)