Large Animal Internal Medicine Resident University of Minnesota Falcon Heights, Minnesota, United States
Abstract: Background- Pituitary pars intermedia dysfunction (PPID) is a common endocrine disorder in aged horses. The Equine Endocrinology Group does not recommend measuring ACTH concentrations following sedation with alpha-2 adrenergic agonists due to changes in ACTH concentrations unrelated to disease; however, there is no literature supporting this recommendation.
Hypothesis/Objectives- Measure the effect of sedation with detomidine and butorphanol, and routine dental procedure on endogenous ACTH concentrations of healthy older horses, and determine how long this effect, if any, persists to improve testing recommendations for PPID.
Animals- Twelve healthy mares of various breeds, aged 8-20 years, from the University herd with no clinical signs or history of PPID.
Methods- Prospective crossover study: horses were sampled during both the fall and spring, undergoing either a sedated oral examination or dental equilibration in alternating fall and spring periods. Blood samples were collected to quantify ACTH concentrations from 0 minutes to 72 hours following sedation.
Results- There was a significant effect of season (p = .004) but not procedure on ACTH concentration. In the fall, sedation was significantly associated with increased ACTH concentrations; however, the effect was no longer significant after 30 minutes (p < .001). There was no significant effect of sedation detected on ACTH concentration in the spring.
Conclusions and Clinical Importance- Season and timing of sample collection following sedation influenced ACTH concentration. This effect was transient, and PPID sampling can be performed 30 minutes after sedation. It is unknown whether results would differ in horses with PPID.
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