Effect of dexmedetomidine on the minimum infusion rate of propofol preventing movement in dogs.

OBJECTIVE: To determine the effect of dexmedetomidine on induction dose and minimum infusion rate of propofol preventing movement (MIRNM ).

STUDY DESIGN: Randomized crossover, unmasked, experimental design.

ANIMALS: Three male and three female healthy Beagle dogs weighing 10.2 ± 2.8 kg.

METHODS: Dogs were studied on three occasions at weekly intervals. Premedications were 0.9% saline (treatment P) or dexmedetomidine (1 μg kg-1 , treatment PLD; 2 μg kg-1 , treatment PHD) intravenously. Anesthesia was induced with propofol (2 mg kg-1 and then 1 mg kg-1 every 15 seconds) until intubation. Anesthesia was maintained for 90 minutes in P with propofol (0.5 mg kg-1 minute-1 ) and saline, in PLD with propofol (0.35 mg kg-1 minute-1 ) and dexmedetomidine (1 μg kg-1 hour-1 ), and in PHD with propofol (0.3 mg kg-1 minute-1 ) and dexmedetomidine (2 μg kg-1 hour-1 ). The stimulus (50 V, 50 Hz, 10 ms) was applied to the antebrachium, and propofol infusion was increased or decreased by 0.025 mg kg-1 minute-1 based on a positive or negative response, respectively. Data were analyzed using a mixed-model anova and presented as mean ± standard error.

RESULTS: Propofol induction doses were 8.68 ± 0.57 (P), 6.13 ± 0.67 (PLD) and 4.78 ± 0.39 (PHD) mg kg-1 and differed among treatments (p < 0.05). Propofol MIRNM values were 0.68 ± 0.13, 0.49 ± 0.16 and 0.26 ± 0.05 mg kg-1 minute-1 for P, PLD and PHD, respectively. Propofol MIRNM decreased 59% in PHD (p < 0.05). Plasma propofol concentrations were 14.04 ± 2.30 (P), 11.30 ± 4.30 (PLD) and 7.96 ± 0.72 (PHD) μg mL-1 and dexmedetomidine concentrations were 0.68 ± 0.12 (PLD) and 0.89 ± 0.08 (PHD) ng mL-1 at MIRNM determination.

CONCLUSIONS AND CLINICAL RELEVANCE: Dexmedetomidine (1 and 2 μg kg-1 ) decreased propofol induction dose. Dexmedetomidine (2 μg kg-1 hour-1 ) resulted in a significant decrease in propofol MIRNM .