Clinical evaluation of intranasal midazolam and alfaxalone for induction of anaesthesia in rabbits

The aim of this experimental, descriptive study was to evaluate feasibility, safety and side effects of alfaxalone and midazolam by intranasal instillation for anaesthesia induction in rabbits. We included 26, healthy, female New Zealand White Rabbits undergoing general anaesthesia in context of a study to test different coatings for stifle joint endoprosthesis. Midazolam (0.1 mg/kg) and alfaxalone 3 mg/kg (group 1) or 4 mg/kg (group 2) were mixed and administered intranasally. The number of sneezes, swallows and evasive attempts were recorded. Time to lateral recumbency, presence of salivation, nystagmus, induction and intubation qualities were scored. If intubation was not possible, a top-up of 1 mg/kg alfaxalone was administered intranasally. If still not sufficient, anaesthesia was induced by mask-insufflation of isoflurane. Data were analysed using IBM SPSS Statistics 30.0.0.0 and non-parametric data compared using either a Mann-Whitney test or a chi-square test. Overall, 10 animals assigned to group 1 and 16 animals to group 2 were included in the study. In 24/26 rabbits (92.3%) no significant complications were noted. One rabbit showed 20 s of apnoea after induction and one rabbit died during induction. Top-up dosages of alfaxalone were necessary in three cases and in two of these three, isoflurane administration was also required to complete anaesthetic induction. The median time to lateral recumbency was 32.5 s in group 1 and 15 s in group 2. By intranasal application of midazolam with alfaxalone at both dosages, the anaesthetic state was induced shortly after application.