Base excess, strong ion difference, and expected compensations: as simple as it is.

The main purpose of this article is to provide some practical insights into acid-base disorders interpretation, comparing the three most widespread diagnostic approaches. After a brief summary of the history of blood gas analysis and the shift from a purely chemical approach to more clinically useful applications, the pros and cons of the different methodologies are compared and discussed. Reviewing the most important publications in the field, the authors attempt to show that each diagnostic strategy is acceptable, although the one based on base-excess calculation perhaps seems too 'rough' to understand the mixed disorders, whereas the Stewart approach is attractive from a chemical point of view, but unsuitable for the emergency physician because of the cumbersome calculations needed. Finally, the anion gap and 'expected compensation' approach seems to be more comprehensive and feasible at the bedside.