Comparison of Intraoperative Behavioral and Hormonal Responses to Noxious Stimuli between Mares Sedated with Caudal Epidural Detomidine Hydrochloride or a Continuous Intravenous Infusion of Detomidine Hydrochloride for Standing Laparoscopic Ovariectomy

Abstract

To compare the presence or absence of pain, pain-related behavioral responses, and hormonal responses to noxious stimuli during standing laparoscopic ovariectomy in mares sedated with continuous intravenous (IV) detomidine infusion and caudal epidural detomidine. A double blind prospective study. Mares (n=12) Mares were divided into 2 treatment groups; 6 were sedated using continuous IV detomidine infusion and 6 were sedated with caudal epidural detomidine. All mares received IV xylazine (0.33 mg/kg) and butorphanol tartrate (5 mg) premedication before detomidine administration. Venous blood samples were taken to assess serum cortisol levels in each mare at 4 time points: a baseline cortisol measurement after the mares' arrival to the clinic, 10 minutes before surgery, at the removal of the 2nd ovary, and 10 minutes postsurgery. Two surgeons performed bilateral ovariectomy and at 8 time points involving surgical manipulations, noted the presence or absence of pain (yes/no) and scored the patient's response on a 10 cm visual analogue scale (VAS) for pain assessment with 0 indicating no pain responses and 10 cm indicating pain so severe that the mare required additional sedation or analgesia to complete the procedure. Each mare was also assigned a VAS score by each surgeon for the overall satisfaction of analgesia during the entire procedure. Serum cortisol levels between the 2 detomidine administration groups differed significantly at the baseline (precortisol) measurement but not at the 3 remaining time points. Seven of the procedures within the surgeries did not differ significantly in VAS scores between the 2 groups. The initial grasp of the left ovary (the 1st ovary) in the continuous infusion group had a significantly higher (P=.05) median VAS score compared with the caudal epidural group. Mares sedated with a continuous IV infusion of detomidine have similar hormonal and behavioral responses to painful stimuli during standing laparoscopic ovariectomy as mares sedated with caudal epidural detomidine. Sedation using a continuous IV infusion of detomidine can be used for laparoscopic ovariectomy in mares.