Analysis of the parameters, traditional or not, for the evaluation of the metabolic acidosis


Despite huge progress in acid–base knowledge, several confusing, irrational and controversial issues still remain. Acid-base disturbances have been usually evaluated with the traditional Henderson-Hasselbach method and with BE evaluation that seem inadequate since they define the magnitude of metabolic acidosis rather than its cause.

Some studies have shown that the traditional approach is often not able to highlight the complicated acid-base disorders in critically ill patients; in these subjects, the possibility to identify tissue acids could offer a greater prognostic value than the evaluation of traditional parameters. An alternative approach is the Stewart’s physiochemical method that defines the aetiology of a metabolic acidosis by quantifying the tissue acids. But the clinical utility of this method is limited due to its mathematical complexity.

Therefore, some parameters of simplification were proposed in order to allow greater clinical applicability of this system. Specifically, it was observed that in the presence of metabolic acidosis, the chloride/sodium ratio (Cl-/Na+ ratio) or the sodium-chloride difference (DiffNa-Cl) would be useful indicators of the presence of unmeasured anions (UMA) and/or lactate.

Key words: acid-base imbalances, chloride and sodium ratio, metabolic acidosis, Stewart’s method

Full text of the article is available in Italian.