Cortisol (hydrocortisone) disappearance rate and pathophysiologic changes after bilateral adrenalectomy in equids

Area of Science:

• Veterinary Medicine
• Equine Physiology
• Endocrinology

Background:

• Bilateral adrenalectomy (BADX) is a critical surgical procedure.
• Understanding the physiological impact of adrenal hormone deficiency in equids is essential for veterinary care.

Purpose of the Study:

• To investigate the survival times and physiological responses of ponies and horses following bilateral adrenalectomy (BADX).
• To determine the biological half-life and elimination kinetics of cortisol in horses post-BADX.

Main Methods:

• Six ponies and one horse underwent bilateral adrenalectomy (BADX).
• Survival times were recorded without corticosteroid supplementation.
• Cortisol biological half-life was estimated.
• Serum electrolyte concentrations and packed cell volume (PCV) were analyzed.
• Electrolyte clearance was calculated using creatinine clearance.

Main Results:

• Two of seven animals survived 24 and 72 hours post-BADX without supplemental corticosteroids.
• The biological half-life of cortisol was determined to be 2.1 ± 0.6 hours, with biphasic disappearance in horses.
• Pathophysiological changes included increased serum sodium, chloride, and PCV, with decreased serum potassium.
• Electrolyte clearance showed an inverse correlation with serum electrolyte changes.

Conclusions:

• Bilateral adrenalectomy (BADX) in equids leads to rapid physiological disturbances and limited survival without corticosteroid support.
• Cortisol kinetics in horses exhibit distinct redistribution and elimination phases.
• The study highlights significant electrolyte imbalances following adrenalectomy in these species.