Effect of different doses of dexmedetomidine on median effective concentration of propofol for anesthesia induction: a randomized controlled trial.

OBJECTIVE: Dexmedetomidine, a highly selective α2-adrenergic receptor agonist with sedative and analgesic properties, is used as an anesthetic adjunct. We determined the effects of different dexmedetomidine doses on the median effective concentration (EC50) of propofol and bispectral index (BIS) values during anesthesia induction. PATIENTS AND METHODS: This randomized, prospective, case-control clinical trial involved 120 patients (56 women; physical status, American Society of Anesthesiologists grades I or II) scheduled to undergo surgery requiring general anesthesia from July 15th, 2014 to June 15th, 2015. The patients were divided into groups of 30 and received dexmedetomidine (0.5 µg/kg, group L; 0.75 µg/kg, group M; 1 µg/kg, group H) with propofol for loss of consciousness or propofol only (control group, group C). EC50, BIS, hemodynamics, and side effects were assessed. RESULTS: The EC50 of propofol was significantly lower in the dexmedetomidine groups than in group C, and decreased with increasing dexmedetomidine dose (p < 0.05). BIS values significantly decreased after 2 min of dexmedetomidine infusion in all dexmedetomidine groups; the values at 8 and 10 min were lower in the dexmedetomidine groups than in group C. The heart rate was lower in the dexmedetomidine groups than in group C. The incidence of bradycardia at loss of consciousness increased with increasing dexmedetomidine dose. CONCLUSIONS: Dexmedetomidine significantly and dose-dependently reduced the EC50 of propofol and BIS values during anesthesia induction. A loading dexmedetomidine dose of 0.5 µg/kg significantly reduced the EC50 of propofol and BIS value, and was associated with a lower incidence of bradycardia than higher doses.