Co-induction of anaesthesia with alfaxalone and midazolam in dogs: a randomized, blinded clinical trial

Abstract

ObjectiveTo qualitatively assess the co-induction of anaesthesia with midazolam and alfaxalone and to determine cardiovascular or respiratory alterations compared with alfaxalone alone. Study designA randomized, blinded, clinical trial. AnimalsA total of 29 American Society of Anesthesiologists grade I or II, client-owned dogs undergoing elective orthopaedic or soft tissue surgery. MethodsAll dogs received 0.02 mg kg–1 acepromazine and 0.3 mg kg–1 methadone intramuscularly 30 minutes prior to anaesthesia. Measurements of heart rate (HR), respiratory frequency and blood pressure (BP) were assessed pre-induction and at 0, 2 and 5 minutes post-induction. Anaesthesia was induced with 0.5 mg kg–1 alfaxalone followed by either 0.4 mg kg–1 midazolam intravenously (group M) or an equal volume of saline (group S). Conditions were assessed for intubation and further boluses of 0.25 mg kg–1 alfaxalone were given as required. Response to co-induction, ease of intubation and quality of induction were scored, and total dose of alfaxalone required for intubation was recorded.Repeated measures one-way analysis of variance with post hoc Tukey’s test was used to assess within group changes over time and Student t tests were used to compare between groups. Incidence of apnoea was assessed using a Fisher’s exact test. Data are shown as mean ± standard deviation. ResultsGroup M included 14 dogs and group S 15 dogs. There was a significant difference in the total dose of alfaxalone required for intubation, 0.65 ± 0.20 mg kg–1 group M and 0.94 ± 0.26 mg kg–1 group S (p = 0.002). Apnoea occurred significantly more frequently in group M (p = 0.007). There were no clinically significant differences in HR or BP at the measured time points between groups. Conclusions and clinical relevanceCo-induction with midazolam had significant alfaxalone-sparing effects with no clinically detectable cardiovascular changes. Apnoea is common after co-induction.