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.