[The difference and ratio between serum concentrations of natrium and chlorides in patients with hyponatremia].

UNLABELLED: The differential diagnosis of hyponatremia is often difficult. This most frequently occurring disorder of the water and electrolyte metabolism is frequently connected with deviations relating to the acid-base balance (ABB). This survey analyzes the relationship between the changes of the volume of body fluids and ABB and infers to what extent the analysis of combinations of the two disorders can support the differential diagnosis of different forms of hyponatremia (differentiation between the dilution vs. depletion forms). The changes of the total water volume (CTV) and ABB may be presented at the same time in the values of the difference and ratio between serum concentrations of natrium and chlorides (SNa+ - SCl-; SNa+/SCl-). The changes of these quantities are analyzed in the models of pathologies connected through hyponatremia and ABB related deviations: (i) retention of solute-free water (hyponatremia associated with dilution acidosis); (ii) retention Na+ in combination with water retention (hyponatremia associated with dilution and hyperchloremic acidosis); (iii) depletion Na+ combined with water depletion (depletion hyponatremia combined with hypochloremic alkalosis), and (iv) combination of dilution and depletion (hyponatremia which may be associated with different ABB related deviations). This survey specifies the extent to which the applied models are consistent with the existing clinical findings and experience. The examinations SNa+ - SCl- and SNa+/SCl- rely only on routinely used laboratory test methods. Monitoring of these quantities may contribute to continuous assessment of the effect of a chosen therapy.

KEY WORDS: acid-base balance - depletion hyponatremia - differential diagnosis of hyponatremia - dilution hyponatremia - hyponatremia - retention of solute-free water - body fluid volumes.