Induction dose and recovery quality of propofol and alfaxalone with or without midazolam coinduction followed by total intravenous anesthesia in dogs

To compare propofol and alfaxalone, with or without midazolam, for induction of anesthesia in fentanyl-sedated dogs, and to assess recovery from total intravenous anesthesia (TIVA). Prospective, incomplete, Latin-square study. Ten dogs weighing 24.5 ± 3.1 kg (mean ± standard deviation). Dogs were randomly assigned to four treatments: treatment P-M, propofol (1 mg kg−1) and midazolam (0.3 mg kg−1); treatment P-S, propofol and saline; treatment A-M, alfaxalone (0.5 mg kg−1) and midazolam; treatment A-S, alfaxalone and saline, administered intravenously (IV) 10 minutes after fentanyl (7 μg kg−1) IV. Additional propofol or alfaxalone were administered as necessary for endotracheal intubation. TIVA was maintained for 35–55 minutes by infusions of propofol or alfaxalone. Scores were assigned for quality of sedation, induction, extubation and recovery. The drug doses required for intubation and TIVA, times from sedation to end of TIVA, end anesthesia to extubation and to standing were recorded. Analysis included a general linear mixed model with post hoc analysis (p < 0.05). Significant differences were detected in the quality of induction, better in A-M than A-S and P-S, and in P-M than P-S; in total intubation dose, lower in P-M (1.5 mg kg−1) than P-S (2.1 mg kg−1), and A-M (0.62 mg kg−1) than A-S (0.98 mg kg−1); and lower TIVA rate in P-M (268 μg kg−1 minute−1) than P-S (310 μg kg−1 minute−1). TIVA rate was similar in A-M and A-S (83 and 87 μg kg−1 minute−1, respectively). Time to standing was longer after alfaxalone than propofol, but was not influenced by midazolam. Addition of midazolam reduced the induction doses of propofol and alfaxalone and improved the quality of induction in fentanyl-sedated dogs. The dose rate of propofol for TIVA was decreased.