Pain assessment in sheep subjected to rumenotomy according to sedation protocol: xylazine vs xylazine+ ketamine

Abstract

The study evaluated the effect of xylazine administration on intraoperative and postoperative pain (both at 2 hours and 4 hours) in sheep undergoing rumenotomy, comparing the effect of ketamine application together with xylazine. Ten Canary sheep were used, five were injected with xylazine as a sedative and the other five were administered xylazine followed by ketamine during surgery. Temperature decreased in both protocols after drug administration, but not significantly and with no difference between them (p = 0.9893). Respiratory rate (RF) decreased after xylazine administration, but there was also no significant influence over time (p = 0.236). In heart rate there were significant differences when the variables time (p = 0.02165) and protocol (p = 0.02398) were analyzed separately, observing a relevant decrease between the intraoperative and postoperative period at 2 h (p = 0.0186) and between the mean HR obtained in the xylazine protocol (X) versus those obtained in the xylazine + ketamine protocol (X+K) (p = 0.0460). As for mean arterial pressure (MAP), although it increased after drug administration, there were no significant differences between anesthetic protocols (p = 0.9117). The pain scale adapted to sheep included: increased heart rate, vocalization, pupillary dilation, salivation, mental status, motor activity, posture, and response to wound palpation. The level of pain was reflected by the sum of the scores of the above behaviors. Mean pain scores in the xylazine protocol were higher both intraoperatively and postoperatively at 2 and 4 hours, showing significant differences between protocols (p = 0.02067). It was concluded that ketamine dosing induced deeper anesthesia that relieved intraoperative and postoperative rumenotomy induced pain compared to the use of xylazine as the sole sedative.