New Zealand white rabbits (Oryctolagus cuniculus) are an established in vivo model for the study of structural and functional consequences of vocal-fold vibration. Research design requires invasive laryngotracheal procedures, and the presence of
laryngospasms or
pain responses (or both) hinder phonation-related data collection. Published
anesthesia regimens report
respiratory depression and muscle tone changes and have been unsuccessful in mitigating autonomic laryngeal responses in our protocol. Infusion of
ketamine hydrochloride and
dexmedetomidine hydrochloride in pediatric medicine provides effective
analgesia and sedation for laryngotracheal procedures including intubation and bronchoscopy; however, data evaluating the use of
ketamine-
dexmedetomidine infusion in rabbits are unavailable. This study reports a new infusion regimen, which was used in 58 male New Zealand white rabbits that underwent a nonsurvival laryngotracheal procedure to induce phonotraumatic vocal-fold injury. Animals were sedated by using
ketamine hydrochloride (20 mg/kg IM) and
dexmedetomidine (0.125 mg/kg IM). Maintenance
anesthesia was provided by using continuous rate
intravenous infusion of
ketamine hydrochloride (343 μg/kg/min) and
dexmedetomidine (1.60 μg/kg/min). A stable plane of
anesthesia with no autonomic laryngeal response (
laryngospasm) was achieved in 32 of the 58 rabbits (55%).
Laryngospasms occurred in 25 of 58 animals (43%) and were controlled in 20 cases (80%) by providing 0.33 mL 2% topical
lidocaine, incremental increase in infusion rate, or both. Continuous rate infusion of
ketamine hydrochloride-
dexmedetomidine with prophylactic topical
lidocaine provides a predictable and adjustable surgical plane of
anesthesia, with minimal confounding respiratory and autonomic laryngeal responses, during extended-duration laryngotracheal surgery in rabbits. This regimen should be considered as an alternative to injection maintenance for prolonged, invasive procedures.