Effects of vatinoxan in dogs premedicated with medetomidine and butorphanol followed by sevoflurane anaesthesia: a randomized clinical study.

OBJECTIVE To investigate effects of vatinoxan in dogs, when administered as intravenous (IV) premedication with medetomidine and butorphanol before anaesthesia for surgical castration. STUDY DESIGN A randomized, controlled, blinded, clinical trial. ANIMALS A total of 28 client-owned dogs. METHODS Dogs were premedicated with medetomidine (0.125 mg m-2) and butorphanol (0.2 mg kg-1) (group MB; n = 14), or medetomidine (0.25 mg m-2), butorphanol (0.2 mg kg-1) and vatinoxan (5 mg m-2) (group MB-VATI; n = 14). Anaesthesia was induced 15 minutes later with propofol and maintained with sevoflurane in oxygen (targeting 1.3%). Before surgical incision, lidocaine (2 mg kg-1) was injected intratesticularly. At the end of the procedure, meloxicam (0.2 mg kg-1) was administered IV. The level of sedation, the qualities of induction, intubation and recovery, and Glasgow Composite Pain Scale short form (GCPS-SF) were assessed. Heart rate (HR), respiratory rate (fR), mean arterial pressure (MAP), end-tidal concentration of sevoflurane (Fe'Sevo) and carbon dioxide (Pe'CO2) were recorded. Blood samples were collected at 10 and 30 minutes after premedication for plasma medetomidine and butorphanol concentrations. RESULTS At the beginning of surgery, HR was 61 ± 16 and 93 ± 23 beats minute-1 (p = 0.001), and MAP was 78 ± 7 and 56 ± 7 mmHg (p = 0.001) in MB and MB-VATI groups, respectively. No differences were detected in fR, Pe'CO2, Fe'Sevo, the level of sedation, the qualities of induction, intubation and recovery, or in GCPS-SF. Plasma medetomidine concentrations were higher in group MB-VATI than in MB at 10 minutes (p = 0.002) and 30 minutes (p = 0.0001). Plasma butorphanol concentrations were not different between groups. CONCLUSIONS AND CLINICAL RELEVANCE In group MB, HR was significantly lower than in group MB-VATI. Hypotension detected in group MB-VATI during sevoflurane anaesthesia was clinically the most significant difference between groups