Effects of frusemide on electrolyte and acid-base balance during exercise

This study was undertaken to evaluate the effects of frusemide on the concentration of plasma electrolytes and the relationship between changes in electrolyte concentration and the simultaneous changes in acid-base balance in arterial and venous blood during intense exercise. Five exercise-conditioned Thoroughbred horses were exercised on a high-speed treadmill at a slope of 10% at speeds known to exceed VO2max. Horses participated in 3 randomised exercise trials in which they received either placebo (control), low-dose frusemide (0.5 mg/kg bwt), or high-dose frusemide (1.0 mg/kg) 4 h prior to exercise. Arterial and mixed venous blood samples were drawn before, during and after intense exercise. Packed cell volume (PCV), plasma protein, plasma electrolyte, plasma lactate concentrations and acid-base balance were determined. Frusemide at both dosages induced a significant metabolic alkalosis associated with a decrease in plasma çhloride[ in both arterial and mixed venous blood. There was a highly significant correlation between the strong ion difference (SID) and bicarbonate[ in all blood samples. The effects of frusemide on electrolyte concentration and acid-base balance were largely due to changes in SID.