The use of elements of the Stewart model (Strong Ion Approach) for the diagnostics of respiratory acidosis on the basis of the calculation of a value of a modified anion gap (AGm) in brachycephalic dogs

Abstract

Apart from the HH equation, the acid-base balance of an organism is also described by the Stewart model, which assumes that the proper insight into the ABB of the organism is given by an analysis of: pCO 2 , the difference of concentrations of strong cations and anions in the blood serum -SID, and the total concentration of nonvolatile weak acids -Acid total. The notion of an anion gap (AG), or the apparent lack of ions, is closely related to the acid-base balance described according to the HH equation. Its value mainly consists of negatively charged proteins, phosphates, and sulphates in blood. In the human medicine, a modified anion gap is used, which, including the concentration of the protein buffer of blood, is, in fact, the combination of the apparent lack of ions derived from the classic model and the Stewart model. In brachycephalic dogs, respiratory acidosis often occurs, which is caused by an overgrowth of the soft palate, making it impossible for a free air flow and causing an increase in pCO 2 -carbonic acid anhydride The aim of the present paper was an attempt to answer the question whether, in the case of systemic respiratory acidosis, changes in the concentration of buffering ions can also be seen. The study was carried out on 60 adult dogs of boxer breed in which, on the basis of the results of endoscopic examination, a strong overgrowth of the soft palate requiring a surgical correction was found. For each dog, the value of the anion gap before and after the palate . The values of AG calculated for the dogs before and after the procedure fell within the limits of the reference values and did not differ significantly whereas the values of AG m calculated for the dogs before and after the procedure differed from each other significantly. Conclusions: 1) On the basis of the values of AG m obtained it should be stated that in spite of finding respiratory acidosis in the examined dogs, changes in ion concentration can also be seen, which, according to the Stewart theory, compensate metabolic ABB disorders 2) In spite of the fact that all the values used for calculation of AG m were within the limits of reference values, the values of AG m in dogs before and after the soft palate correction procedure differed from each other significantly, which proves high sensitivity and usefulness of the AG m calculation as a diagnostic method.

Use of Elements of the Stewart Model (Strong Ion Approach) – SID3, SID4, Atot/A−, SIDe and SIG for the Diagnostics of Respiratory Acidosis in Brachycephalic Dogs

“…While planning the study, it was assumed that by the 14 th day after surgery, the surgical wound healing process, swelling of the operated area and the influence of the drugs used during the surgery would end, and therefore the results obtained would be credible. A sample of arterial blood was drawn using the method described by Sławuta et al (2015). With the use of an Osmetech OPTI CCA Blood Gas Analyzer unit, the following was determined in the drawn sample of arterial blood: blood pH, HCO 3 -, and pCO 2 .…”

“…The notion of an apparent strong ion gap -SIG also derives from the Stewart model. Unlike the classic anion gap (AG), whose diagnostic significance has already been described in detail (Sławuta et al 2015), the concentration of albumins and phosphates is included in the calculation of SIG, thus, its diagnostic value is greater compared to the anion gap (Kellum 1995, Wooten 2004. In addition, the numerical value of SIG is influenced by the following, which are not determined on a routine basis: lactate, ketoanions, β-hydroxybutate, acetoacetate, sulphates and anions associated with uraemia.…”

“…In addition, the numerical value of SIG is influenced by the following, which are not determined on a routine basis: lactate, ketoanions, β-hydroxybutate, acetoacetate, sulphates and anions associated with uraemia. SIG is, in a sense, a developed concept of a modified anion gap (AG m ) applied in the diagnostics of ABB disorders in people and animals (Oh 2010, Sławuta et al 2015. Some authors (Fencl et al 2000, Hooper et al 2014a) treat the completion of the Stewart theory with an analysis of changes in the concentrations of: Cl -, albumins, phosphorus and lactate as the third model that describes the ABB of the organism, known as the semiquantitive approach.…”

“…Some authors (Fencl et al 2000, Hooper et al 2014a) treat the completion of the Stewart theory with an analysis of changes in the concentrations of: Cl -, albumins, phosphorus and lactate as the third model that describes the ABB of the organism, known as the semiquantitive approach. The differences between SIG, AG and AG m , calculation methods and their practical application in dogs have been described in detail (Sławuta et al 2015).…”

“…However, the authors of this study, taking into account the results obtained earlier (Sławuta et al 2015), assumed that if respiratory acidosis is of the systemic type then the concentration of ions which buffer the ABB disorders on an intracellular and pericellular level should also change. Thus, the goal of the study was to find out whether, in the course of respiratory acidosis, the values of SID 3 , SID 4 , Atot/A -, SID e and SIG change.…”