RESUMO
OBJECTIVE: To compare the topographic modifications and tactile sensitivity of the pharynx and larynx after administration of four sedative and analgesic protocols in standing horses. STUDY DESIGN: Experimental, observer-blinded, crossover study. ANIMALS: Eight healthy mares. METHODS: Five protocols were evaluated: 1) xylazine and butorphanol administered intravenously (IV); 2) detomidine and butorphanol administered IV; 3) xylazine administered IV and lidocaine topically; 4) detomidine administered IV and lidocaine topically and 5) no analgesia or sedation (control). Quality of sedation, head height and sudden head movements were recorded. The degree of arytenoid cartilage displacement, the degree of pharyngeal collapse and the occurrence of soft palate displacement were scored using standardized scales. Tactile sensitivity was tested on 10 different pharyngeal and laryngeal regions using an atraumatic transendoscopic probe. Statistical analysis was performed using linear or generalized mixed-effects models. RESULTS: Head height was significantly decreased in protocols with xylazine (p = 0.002). Head movements were significantly increased in protocols with butorphanol (p = 0.0001). No changes in abduction grade or degree of soft palate displacement were observed between all sedative protocols and the control group. Pharyngeal collapse was significantly more frequent in protocols with lidocaine (p < 0.001) or xylazine (p = 0.017). For the pharyngeal regions, no tactile sensitivity difference was observed between the control and treatment protocols. All treatment protocols led to greater desensitization of all the laryngeal regions compared with the control protocol. CONCLUSION AND CLINICAL RELEVANCE: All the protocols provided adequate sedation and analgesia for the manipulation of the larynx and pharynx but significant differences were noted. Xylazine produces a more profound sedation compared with detomidine, but can induce dorsal pharyngeal collapse. Lidocaine caused pharyngeal collapse and its use should be limited to the target area. Butorphanol can be added to improve analgesia in the other regions but frequent head jerking can be expected.