Randomised clinical trial comparing intramuscular alfaxalone and butorphanol sedation with or without midazolam in hyperthyroid cats

Objectives:
The sedation quality of intramuscular (IM) alfaxalone and butorphanol in combination with midazolam was investigated in hyperthyroid cats undergoing suitability assessment for radioiodine treatment.

Methods:
A total of 60 hyperthyroid cats undergoing diagnostic investigations were randomly allocated to receive butorphanol (0.3 mg/kg IM) and midazolam (0.2 mg/kg IM) with either alfaxalone (2 mg/kg IM) (BMA2) or alfaxalone (3 mg/kg IM) (BMA3), or butorphanol (0.3 mg/kg IM) with alfaxalone (3 mg/kg IM) (BA3). If required, additional alfaxalone (0.2 mg/kg) was administered intravenously. Cat Stress Score, response to injection, time to lateral recumbency, sedation score at 10, 15 and 20 mins and subsequent 10-min intervals, additional alfaxalone requirements, and time to first administration, recovery quality (excellent, fair, poor) and adverse effects were assessed. Thyroxine concentrations, gabapentin treatment and assessors were recorded. Heart and respiratory rate and arterial haemoglobin saturation were monitored every 5 mins. Data were compared using χ2 and Kruskal–Wallis testing. The multidimensional sedation score and predictors of sedation score were analysed using a mixed effect and linear regression model, respectively (P<0.05).

Results:
No significant predictors for sedation quality were identified. In all groups, the median sedation score was considered good and the median recovery score was fair. The sedation score over time across groups and cardiorespiratory variables were not significantly different. Additional alfaxalone was administered in 53 cats. In group BA3, additional alfaxalone was required significantly earlier (P = 0.043). Although sedated, muscle twitching was a commonly observed adverse effect in all groups, but head pawing was significantly increased in BA3 (P = 0.014).

Conclusions and relevance:
Sedation and recovery quality were satisfactory with all protocols but the addition of midazolam prolonged sedation.