Clinical pathologic alterations in horses during a water deprivation test

Area of Science:

• Equine physiology
• Clinical pathology
• Renal function

Background:

• Understanding the physiological response to dehydration is crucial for equine health management.
• Electrolyte and renal function parameters provide insights into hydration status.
• Accurate measurement of urine concentration is essential for diagnosing dehydration.

Purpose of the Study:

• To investigate clinical pathologic changes in horses subjected to 72-hour water deprivation.
• To establish reference values for electrolyte clearance relative to creatinine clearance (%CLCRX).
• To compare the efficacy of different urine concentration measurement techniques.

Main Methods:

• A 72-hour water deprivation test was conducted on 12 horses.
• Electrolyte clearance (%CLCRX) and acid-base values were measured.
• Plasma protein and packed cell volume (PCV) were monitored.
• Urine osmolality (osmometry) and specific gravity (refractometry) were compared.

Main Results:

• Sodium (Na) excretion increased significantly during water deprivation, with a subsequent decrease in %CLCRNa after 48 hours.
• Plasma protein was a more sensitive indicator of dehydration than PCV.
• Urine specific gravity correlated well with urine osmolality initially, but this correlation diminished after 48 hours.
• Minimal significant changes in acid-base values were observed after 72 hours.

Conclusions:

• Horses exhibit significant alterations in electrolyte clearance and excretion patterns during water deprivation.
• Plasma protein concentration is a superior indicator of dehydration in horses compared to PCV.
• The reliability of urine specific gravity as a measure of urine concentration decreases with prolonged dehydration.