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

Abstract

ObjectiveTo determine the effect of dexmedetomidine on induction dose and minimum infusion rate of propofol preventing movement (MIRNM). Study designRandomized crossover, unmasked, experimental design. AnimalsThree male and three female healthy Beagle dogs weighing 10.2 ± 2.8 kg. MethodsDogs 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. ResultsPropofol 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 relevanceDexmedetomidine (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.