Effects of prerace exercise, frusemide, sex and ambient temperature on blood sodium, bicarbonate and pH values in standardbred horses.

Analysis of data collected at racetracks showed that temperature, the diuretic drug, frusemide, exercise, temperature/exercise interaction and sex/age had significant (P < 0.05) effects on pH and bicarbonate ion concentration (P < 0.01). Sodium concentrations were significantly (P < 0.001) affected by temperature and frusemide. We suggest that the normal range limits for blood sodium, bicarbonate and pH used in prerace testing procedures should be adjusted for ambient temperature and for horses given frusemide and/or prerace exercise. These adjustments should improve the precision of detecting illegal alkalogenic agents and incidence of false positive and false negative test results.