EFFECT OF FUROSEMIDE ON PHYSIOLOGICAL VARIABLES IN EXERCISING HORSES

Twelve horses (6 Standardbreds and 6 Thoroughbreds) received IM inject ions of furosemide (250 mg) or physiologic saline solution and perform ed standard exercise tests, to assess the effects of furosemide and br eed on blood gas values, PCV, plasma lactate concentration, and heart rate during exercise. After furosemide administration, arterial and ve nous blood pH values were significantly (P < 0.05) increased. Partial pressures of O-2 and CO2 in arterial blood and of CO2 in venous blood (Pa-O2, Pa-CO2, and PVCO2, respectively) were unaffected by furosemide treatment, whereas venous partial pressures of O-2 (PVO2) were signif icantly (P < 0.05) less during exercise after furosemide treatment, su ggesting an increase in oxygen uptake by the exercising muscles or a c hange in cardiac output. A significant (P < 0.05) difference was found between Thoroughbred and Standardbred values for arterial and venous pH, Pa-O2, Pa-CO2, plasma lactate concentration, and heart rate, sugge sting that Standardbreds exercised at a relatively higher work rate th an did Thoroughbreds.