Traditional and quantitative analysis of acid‐base and electrolyte imbalances in horses competing in cross‐country competitions at 2‐star to 5‐star level

Abstract Background Early recognition and management of acid‐base, fluid, and electrolyte disorders are crucial for the maintenance of health and performance in equine athletes. Objectives To analyze changes in acid‐base and electrolyte status associated with exercise during cross‐country competitions at different levels using traditional and quantitative approaches. Animals Thirty‐eight eventing horses. Methods Prospective observational study. Jugular venous blood samples were collected before and after the cross‐country test of 25 international eventing competitions ranging from 2‐star (formerly 1‐star) to 5‐star (formerly 4‐star) level. Blood gas analysis was performed to determine pH, pCO2, Na+, Cl−, and K+ and calculate HCO3−, tCO2 base excess (BEECF), anion gap (AG), strong ion difference calculated from Na+, K+, Cl−, and lactate− (SID4), strong ion difference calculated from Na+, K+, and Cl− (SID3), strong ion gap (SIG), and total nonvolatile weak buffer concentration (Atot). Postexercise acid‐base imbalances, diagnosed on the basis of the traditional approach, and the simplified strong ion model were compared. Results Significant decreases in pH, Cl−, SID4, pCO2, HCO3−, tCO2, and BEECF as well as increases in K+, SID3, AG, TP, and Atot were observed between pre‐ and postexercise samples. The changes in acid‐base parameters were significantly affected by the competition level. Using the strong ion approach, a higher proportion of horses was diagnosed with postexercise metabolic acidosis. Conclusions and Clinical Importance Regarding the complex acid‐base changes in horses competing at cross‐country competitions, the quantitative approach provided a more detailed analysis of the different factors contributing to acid‐base balance than did the traditional approach.