The median effective dose of dexmedetomidine for laryngeal mask airway insertion with propofol 2.0 mg/kg.

Abstract

BACKGROUND: Dexmedetomidine can be used as a co-induction agent to facilitate

laryngeal mask airway (LMA) insertion with minimal effect on respiratory

function. The purpose of the study was to determine the median effective dose

(ED50) of dexmedetomidine to facilitate LMA insertion during anaesthesia

induction with propofol 2.0 mg/kg without neuromuscular blockade. METHODS:

Twenty-two patients, whose American Society of Anesthesiologists physical status

was I or II with ages between 18 and 60 years undergoing minor orthopaedic or

gynaecological surgery, were enrolled. After an injection of pre-determined bolus

dose of dexmedetomidine over 2 min, anaesthesia was induced with propofol 2.0

mg/kg. The modified Dixon's up-and-down method was used to determine the bolus

dose of dexmedetomidine, starting from 0.5 mug/kg (step size; 0.1 mug/kg). LMA

insertion was conducted 90 s after the propofol injection, and the response of

patients was categorized as either 'success' or 'failure.' RESULTS: Insertion of

the LMA was unsuccessful in 12 of 22 patients. The ED50 (95% confidence interval)

of dexmedetomidine for successful LMA insertion with propofol 2.0 mg/kg was 0.55

(0.44-0.66) mug/kg. Bradycardia occurred in four patients, and seven patients had

an apneic episode. CONCLUSION: The single dose of dexmedetomidine for successful

LMA insertion to be feasible in 50% of patients was 0.55 mug/kg during

anaesthesia induction with propofol 2 mg/kg.