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Preexercise hypervolemia does not affect arterial hypoxemia in Thoroughbreds performing short-term high-intensity
Murli Manohar1, Thomas E Goetz, Aslam S Hassan
1Department of Veterinary Biosciences, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA. mmanohar@uiuc.edu
Journal of Applied Physiology (Bethesda, Md. : 1985)
|February 4, 2003
Summary
Preexercise hypervolemia did not worsen arterial hypoxemia in Thoroughbred horses during maximal exercise. However, it did reduce the oxygen difference between arterial and mixed venous blood during intense exercise.
Area of Science:
- Equine Sports Medicine
- Exercise Physiology
- Cardiovascular Physiology
Background:
- Hydration status is crucial for athletic performance and thermoregulation in horses.
- Previous research indicated preexercise hyperhydration worsened arterial hypoxemia in horses during submaximal exercise.
- The impact of induced hypervolemia on hypoxemia during high-intensity exercise in Thoroughbreds remained unclear.
Purpose of the Study:
- To investigate if preexercise induced hypervolemia accentuates arterial hypoxemia in Thoroughbreds during high-intensity exercise.
- To assess the effects of hypervolemia on blood gases, acid-base balance, and oxygen transport during maximal exertion.
Main Methods:
- Seven healthy, trained Thoroughbred horses underwent two experimental trials (control and hypervolemia) in a randomized order.
- Hypervolemia was induced by administering NaCl solution via nasogastric tube, increasing plasma volume by 18%.
- Horses performed incremental exercise to maximal exertion on a treadmill, with blood samples collected for analysis.
Main Results:
- Both control and hypervolemia trials resulted in significant arterial hypoxemia, hemoglobin desaturation, hypercapnia, acidosis, and hyperthermia during maximal exercise.
- No statistically significant differences in arterial hypoxemia were observed between the control and hypervolemia treatments.
- Hypervolemia significantly attenuated the exercise-induced expansion of the arterial-to-mixed venous blood oxygen content gradient (P < 0.01).
Conclusions:
- Preexercise induced hypervolemia does not significantly affect the severity of arterial hypoxemia in Thoroughbreds during maximal exercise.
- Hemodilution from hypervolemia impacts oxygen content gradient but not the development of exercise-induced hypoxemia.
- Further research is needed to understand the complex interplay of hydration, hypervolemia, and respiratory/cardiovascular responses during intense equine exercise.