Transcript determination of total carbon dioxide in horses tco2 testing

DETERMINATION OF TOTAL CARBON DIOXIDE
IN HORSES
TCO2 TESTING
George Maylin
Phil Lorimer
MILKSHAKES
• Horses develop acidosis during racing
• Acidosis impairs performance
• Originally blamed on lactic acid build-up
• Now known to be accumulation of Hydrogen Ion
• (H+) in tissues. Alters cell metabolism.
• Acidosis prevented and treated with sodium
bicarbonate or baking soda….Milkshakes
CARBON DIOXIDE BUFFERING SYSTEM
• CO2 + H2O
H2CO3
• PH 7.4
HCO3- + H+
Chemical Reaction to Determine TCO2
Specific Ion Electrode
CO2 + H2CO3 + HCO3 - + CO3= + RNHCOO- + H+ →
CO2 + H2O
The pH electrode coated with a silicone rubber membrane is used to measure CO2by a
differential change in pH.
When the sample is mixed with acid, all forms of carbon dioxide are converted to their
gaseous form.
The gas diffuses through the membrane and lowers the pH of a bicarbonate solution.
The change in pH is proportional to the carbon dioxide in the sample which is recorded
as a result.
Threshold Values for TCO2
• 39 mmoles TCO2/ml plasma
Furosemide
• 37 mmoles TCO2 /ml plasma
No Furosemide
• 37 mmoles TCO2/ml plasma
For both (Proposed)
• Test sample at least 4 hrs post furosemide
• Test sample within 3 hrs can be problematic
TCO2 mmoles/L
NY Harness Track
Pre Race Samples
No Furosemide
Post Race Samples
Furosemide
Pre Race Samples
Furosemide <3hrs
Post Race Samples
Furosemide > 5 hrs
n= 29
n= 20
n=79
n=35
Range : 29.3-34.4
Range:26.4-33.1
Range: 30-38.5
Range: 27.6-33.8
Ave: 32.0
Ave: 29.5
Ave: 33.4
Ave:29.8
Doses of furosemide not recorded. Usual dose 5ml.
Pre race with furosemide: The higher levels associated with 2hr time interval.
Impact of furosemide can be significant.
Longitudinal Drug Testing
• Testing horses over a period of time.
• Now done in IOC and human athletes.
• Has potential for incriminating as well as exonerating positive
findings.
• “My horse is an outlier”.
Summary
• TCO2 testing to detect alkalinizing agents.
• Must distinguish natural levels of TCO2 from feed supplements
that may have alkalinizing agents in them.
• Detect illegal milkshakes.
• Furosemide can increase the TCO2 levels depending on dose
and time interval between injection and blood sampling.
• Sampling time within 3 hours of injection is problematic.
QUARANTINE PROTOCOL
NY
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Request by trainer for quarantine
Quarantine will last for 3 days
Trainer has 3 days to decide
Quarantine in a secure barn, 24 hr watch for 72 hrs
Access to horse by a pre-determined groom and an additional
designated person. Only in the presence of an investigator
Horse fed hay, oats and water. No electrolytes or supplements
Horse feed supplied by the State
Work schedule negotiated to facilitate feeding times and sampling
Trainer has to pay for security expenses
Tested for TCO2 on arrival and then daily
Split sample testing can be done