Dual-route medetomidine-alfaxalone-butorphanol anesthesia: a refined protocol for balanced anesthesia in male rabbits

Abstract

Injectable anesthesia is widely used in laboratory animals because of its ease of administration and minimal equipment requirements. However, it necessitates careful monitoring as well as thermal and oxygen support. This study evaluated the efficacy of medetomidine-alfaxalone-butorphanol (MAB) anesthesia in male rabbits using a dual-route administration protocol. The anesthetic doses were as follows: medetomidine, 0.2 mg/kg; alfaxalone, 2.0 mg/kg; and butorphanol, 2.0 mg/kg. MAB anesthesia, administered via intravenous and subcutaneous routes, induced rapid and smooth induction, achieving anesthetic scores comparable to those of medetomidine-midazolam-butorphanol (MMB) anesthesia. MAB anesthesia resulted in mild hypothermia during the procedure. Upon atipamezole administration, rabbits under MAB anesthesia exhibited faster recovery of the righting reflex and respiration rate than those under MMB. Importantly, no abnormal behaviors, such as jumping or agitation, were observed during induction or recovery, as reported with alfaxalone use in other species. Both protocols maintained spontaneous breathing, although transient hypoxemia was observed in all rabbits. The dual-route MAB protocol provided effective anesthesia while addressing the limitations of conventional MMB anesthesia in rabbits, suggesting its potential as a refined anesthetic method for this species. Unlike mice, which showed weaker anesthetic effects with MAB compared to MMB, MAB demonstrated superior anesthetic properties in rabbits. This study highlights the importance of species-specific anesthetic protocols and the potential benefits of MAB anesthesia in rabbits, particularly its smooth induction and recovery profile, without adverse behaviors often associated with alfaxalone in other species.