Equine total carbon dioxide testing in Illinois in 2012

Area of Science:

• Equine Sports Medicine
• Clinical Chemistry
• Analytical Toxicology

Background:

• Prolonged strenuous exercise in racehorses can lead to acidemia.
• Blood alkalizing agents are used to counteract acidemia by increasing plasma pH and total carbon dioxide (TCO2) concentration.
• Accurate measurement of TCO2 is crucial, with an administrative threshold of 37.0 mmol/L in Illinois.

Purpose of the Study:

• To report a validated method for measuring TCO2 levels in equine plasma using the Beckman UniCel DxC 600.
• To determine the uncertainty associated with TCO2 measurements.
• To investigate physiological and environmental factors affecting TCO2 concentrations in racehorses.

Main Methods:

• A validated method using Beckman UniCel DxC 600 with a six-point calibration curve (5-50 mmol/L) and controls.
• Uncertainty determination using the Guide to the Expression of Uncertainty in Measurement approach (3% at 99.7% confidence).
• Analysis of covariance to assess correlations between TCO2 levels and factors like gender, breed, Lasix® status, strong ion concentration, collection time, and track location.

Main Results:

• Data collected from 5,199 race samples (134 Thoroughbred, 5,065 Standardbred) with an overall mean TCO2 of 30.5 ± 2.0 mmol/L.
• Gender, breed, furosemide status, collection time, and track location were strongly correlated with TCO2 levels (P < 0.0001).
• TCO2 concentrations were highly correlated with sodium and chloride ion concentrations (P < 0.0001), but not potassium.

Conclusions:

• The validated method provides accurate TCO2 measurements in equine plasma with low uncertainty.
• Several physiological and environmental factors significantly influence TCO2 concentrations in racehorses.
• Strong ion concentrations, particularly sodium and chloride, are highly correlated with TCO2, suggesting potential for doping detection.