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

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-l), 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 [A(T) = 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+, PCO2 decreased after exercise while SID and A(T) increased. 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. (C) 2000 Harcourt Publishers Ltd.