Chloride:Sodium Ratio May Accurately Predict Corrected Chloride Disorders and the Presence of Unmeasured Anions in Dogs and Cats

Abstract

Disorders of chloride and mixed acid–base disturbances are common in veterinary emergency medicine. Rapid identification of these alterations and the presence of unmeasured anions aid prompt patient assessment and management. This study aimed to determine in dogs and cats if site-specific reference values for [Cl−]:[Na+] ratio and [Na+] − [Cl−] difference accurately identify corrected chloride abnormalities and to evaluate the predictive ability of the [Cl−]:[Na+] ratio for the identification of unmeasured anions. A database containing 33,117 canine, and 7,604 feline blood gas and electrolyte profiles was generated. Institution reference intervals were used to calculate site-specific reference values for the [Cl−]:[Na+] ratio and the [Na+] − [Cl−] difference. Contingency tables were used to assess the ability of these values to correctly identify corrected chloride disorders. Unmeasured anions were estimated by calculating strong ion gap (SIG). Continuous variables were compared using the Mann–Whitney U test. Correlations between continuous variables were assessed using Spearman’s rho (rs). In dogs, site-specific reference values for the [Cl−]:[Na+] ratio correctly identified 94.6% of profiles as hyper-, normo-, or hypochloremic. For dogs with normal sodium concentrations, site-specific reference values for the [Na+] − [Cl−] difference correctly identified 97.0% of profiles. In dogs with metabolic acidosis (base deficit > 4.0), [Cl−]:[Na+] ratio and SIG were moderately but significantly negatively correlated (rs −0.592, P < 0.0001). SIG was significantly greater in dogs with metabolic acidosis and hypochloremia compared to those without hypochloremia (P < 0.0001). In cats, site-specific reference values for the [Cl−]:[Na+] ratio correctly identified 93.3% of profiles as hyper-, normo-, or hypochloremic, while site-specific reference values for [Na+] − [Cl−] difference correctly identified 95.1% of profiles. In cats with metabolic acidosis [Cl−]:[Na+] ratio and SIG were moderately significantly negatively correlated (rs −0.730, P < 0.0001). SIG was significantly greater in cats with metabolic acidosis and hypochloremia compared to those without hypochloremia (P < 0.0001). Site-specific values for [Cl−]:[Na+] ratio and [Na+] − [Cl−] difference accurately identify corrected chloride disorders in both dogs and cats and may aid identification of the presence of unmeasured anions.

Diagnostic utility of different models used to assess the acid–base balance in cats with chronic kidney disease

“…The results of the Cl À /Na þ ratio were consistent with those reported by Goggs et al (2017) in all the cats, although they were significantly higher in groups II, III and IV compared to the values found in groups C and I.…”

“…However, the values of the Cl À /Na þ ratio remained within the range provided by Goggs et al (2017) in all the groups (0.74-0.80), including group IV diagnosed with metabolic acidosis based on the Henderson-Hasselbalch equation (HH equation). Based on this study, the upper reference range of the Cl À /Na þ ratio in cats with suspected CKD should approximate 0.77-0.78.…”

“…Values below 0.75 indicate alkalosis, while those above 0.80 indicate acidosis (Fencl et al, 2000). Goggs et al (2017) and Vanova- Uhrikova et al (2017) also supported this idea in their experiment on dogs and cats. The diagnostic criteria for metabolic acidosis used in this study are presented in Table 1.…”

“…Cl À is the principal anion in the extracellular fluid. Hence, it is assumed that a decrease in plasma Cl À increases SID causing hypochloraemic alkalosis, while an increase in plasma Cl À often decreases SID causing hyperchloraemic acidosis (Goggs et al, 2017). Therefore, the statistically significant increase in chlorine concentration, a decrease in HCO 3 À concentration and the unchanged AG value signified hyperchloraemic (i.e.…”

“…Some authors believe that the Cl À /Na þ ratio is a more accurate and better indicator of ABB disorders than AG (Durward et al, 2001;Goggs et al, 2017). In the case of high-AG metabolic acidosis, Durward et al (2001) demonstrated the usefulness of the Cl À /Na þ ratio, which decreased with the decrease of blood Cl À concentrations and an increase in the AG.…”