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.
Keywords: anesthesia; dexmedetomidine; dogs; minimum infusion rate; propofol.
Published by Elsevier Ltd.