Objective: To evaluate the dose of alfaxalone needed for induction of anesthesia following sedation with medetomidine-vatinoxan plus hydromorphone (MVH), dexmedetomidine plus hydromorphone (DH), or hydromorphone (H) alone. A secondary objective included evaluating selected cardiopulmonary variables before, during, and after sedation and general anesthesia with sevoflurane in healthy dogs.
Study design: Prospective, randomized, masked, crossover.
Animals: Eight healthy Beagle dogs, 3-4 years old.
Methods: All dogs received three intramuscular (IM) treatments: H (0.1 mg kg-1), DH (0.005 mg kg-1 + 0.1 mg kg-1, respectively), or MVH (0.01 mg kg-1 + 0.2 mg kg-1 + 0.1 mg kg-1, respectively) at least 6 days apart. General anesthesia was induced with alfaxalone 20 minutes after treatment administration and maintained for 60 minutes with 2.8% sevoflurane (expired). Sedation scores, selected cardiopulmonary variables, and recovery scores were measured before, during, and after anesthesia at selected timepoints. Mixed-effects ANOVA and ANOVA on ranks were used to evaluate differences between treatments, time, and their interaction, and Tukey-Kramer method was used for post hoc analysis (p < 0.05). Data are presented as mean ± SD or median (range).
Results: Dogs given MVH required a lower dose of alfaxalone for induction of anesthesia (0.77 ± 0.4 mg kg-1) compared to DH and H (1.16 ± 0.34 mg kg-1; p = 0.02, 1.13 ± 0.18 mg kg-1; p = 0.02), and had a higher incidence (50%; p = 0.038) and longer duration [median; 10 (0-35) minutes] of hypotension during sevoflurane anesthesia compared to H [0%; 0 (0-0) minutes; p = 0.040] but not DH (p = 0.272).
Conclusions and clinical relevance: Premedication with MVH provided the greatest alfaxalone-sparing effect. However, this treatment was associated with lower arterial pressures and clinically relevant hypotension. Off-label use of medetomidine-vatinoxan before sevoflurane-based anesthesia should be used with caution due to a high incidence of hypotension.
Keywords: alfaxalone; dexmedetomidine; hydromorphone; medetomidine; sevoflurane; vatinoxan.
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