Quantitative analysis of acid–base balance in show jumpers before and after exercise

Abstract

The acid–base status of venous blood was studied in 17 show jumpers before and after exercise using both a traditional and a quantitative approach. Partial pressure of carbon dioxide (PCO2), pH, haemoglobin, and plasma concentrations of sodium (Na+), chloride (Cl–), potasium (K+), ionized calcium (Ca2+), total proteins, albumin, lactate and phosphorus were measured in jugular venous blood samples obtained before and immediately after finishing a show jumping competition. Bicarbonate, anion gap and globulin concentration were calculated from the measured parameters. ‘Quantitative analysis’ of acid–base balance was performed utilising values for three independent variables: PCO2, strong ion difference [SID = (Na++ K++ Ca2+) – (Cl–+ Lact)] and total concentration of weak acids [AT= Alb (1¶23 pH – 6¶31) + Pi (0¶309 pH – 0¶469) 10/30¶97]; plasma concentrations of hydrogen ion ([H+]) were also calculated from these variables using Stewart’s equation. No significant changes in blood pH were detected after the show jumping competition. Exercise resulted in a significant increase in lactate, Na+, K+, haemoglobin, total proteins, albumin, globulin and anion gap, and a decrease in bicarbonate, Cl–and Ca2+. PCO2decreased after exercise while SID and ATincreased. A significant correlation between measured and calculated [H+] was found both before and after exercise. However, individual [H+] values were not accurately predicted from Stewart’s equation. In conclusion, even though pH did not change, significant modifications in the acid–base balance of horses have been found after a show jumping competition. In addition, quantitative analysis has been shown to provide an adequate interpretation of acid–base status in show jumpers before and after exercise.