Comparison of morphological changes and tactile sensitivity of the pharynx and larynx between four standing sedative and analgesic protocols in eight adult healthy horses.

The research article explores the impact of different sedative and analgesic methods on the pharynx and larynx of horses. It specifically investigates the morphological changes and tactile sensitivity of these body parts under four separate treatment protocols.

Research Methodology

• Eight healthy adult horses, who were all mares, were chosen for this experiment.
• The study was built on a crossover model where each horse was exposed to all treatment methods in different stages and an observer-blinded method was used to ensure impartiality in observations.
• In total, four sedative and analgesic protocols were compared against a control group who received no analgesia or sedation.
• The treatments included combinations of intravenous xylazine and butorphanol, intravenous detomidine and butorphanol, intravenous xylazine with topical lidocaine, and intravenous detomidine with topical lidocaine.
• Factors such as the quality of sedation, head height and sudden head movements were recorded.
• Through the use of standardized scales, the positioning and displacement of the arytenoid cartilage and the soft palate, and the degree of pharyngeal collapse were scored.
• Tactile sensitivity of ten different pharyngeal and laryngeal regions was tested using a transendoscopic probe.
• Data was analyzed using linear or generalized mixed-effects models.

Research Findings

• The use of xylazine led to a significant reduction in head height.
• Treatments involving butorphanol resulted in an increased number of head movements.
• No changes were observed in the degree of abduction or soft palate displacement when all the sedative protocols were compared to the control group.
• The incidence of pharyngeal collapse was considerably higher in treatments that included lidocaine or xylazine.
• There was no observed difference in tactile sensitivity in the pharyngeal regions between the control and treatment groups.
• All treatment protocols led to a higher level of desensitization in the laryngeal regions as compared to the control protocol.

Conclusion

• All the protocols were successful in providing adequate sedation and analgesia for manipulation of the larynx and the pharynx of the horses.
• However, the study established that there were significant differences among the protocols. Xylazine produced a more deep-seated sedation compared to detomidine but had the downside of inducing pharyngeal collapse.
• Lidocaine similarly induced pharyngeal collapse and its use was recommended to be limited to the target area.
• Butorphanol, while serving as an effective addition to the treatment regimen to improve analgesia in other areas, had the drawback of causing the horses to jerk their heads more frequently.