The Effects of Anesthesia on Laryngeal Function and Laryngeal/Pharyngeal Trauma in the Horse

Laryngeal paralysis in horses has been reported after inhalational anesthesia and can result in significant morbidity/mortality. The cause of the condition is unclear. The objective of this study was to examine the effects of a standardized anesthetic protocol on laryngeal function and laryngeal/pharyngeal trauma in the peri-anesthetic period in a prospective study. A 30- to 60-second digitalized video clip of laryngeal movement from a standardized endoscopic view was recorded at five time points: before sedation, post-sedation, post-induction, immediately after recovery to standing, and at 24 hours after recovery. A standardized anesthetic regimen was used in all cases. Video clips were randomized and evaluated by two blinded assessors. Each assessor scored each clip for laryngeal function and trauma using previously validated scoring systems. Agreement between assessors was calculated using the mean of the five time-specific weighted kappa statistics. Post-anesthesia laryngeal function and trauma scores were compared with initial scores using the Wilcoxon signed rank test with Bonferroni adjustment. Spearman's rank coefficient was used to assess correlation between trauma and function scores and between anesthetic duration and laryngeal function and trauma scores. There was no significant effect of anesthesia on laryngeal function. Trauma scores were not significantly higher after tracheal intubation. The trauma scoring system requires further validation. There was no correlation between higher trauma scores and laryngeal function or duration and laryngeal function or trauma. Further work is required to evaluate other variables that may affect laryngeal function after anesthesia, using a larger number of horses with varying degrees of laryngeal dysfunction.