A randomized controlled trial of the effect of preoperative dexmedetomidine on the half maximal effective concentration of propofol for successful i-gel insertion without muscle relaxants.

Abstract

Dexmedetomidine is a useful anesthetic adjuvant for general anesthesia. We determined whether preoperative dexmedetomidine administration could reduce the half maximal effective concentration (EC50) of propofol for successful i-gel insertion without muscle relaxants.

Thirty-seven patients were randomly allocated to one of two groups. In the dexmedetomidine group (n = 19), dexmedetomidine (1 A mu g/kg) was loaded for 10 min preoperatively. In the control group (n = 20), the same volume of 0.9 % normal saline was administered in the same manner. The EC50 of propofol for successful i-gel insertion was determined using Dixon's up-and-down method. The EC50 of propofol was calculated as the midpoint concentration after at least six crossover points had been obtained. For successful i-gel insertion, all of the following four factors were required-(1) no major movement of the body within 1 min of insertion, (2) no significant resistance to mouth opening, (3) cough a parts per thousand currency sign2, and (4) visible square wave capnogram without air leakage at a peak airway pressure of < 10 cmH(2)O. Mean blood pressure (MBP) and heart rate (HR) were monitored during the peri-insertion period of i-gel.

The EC50 of propofol for successful i-gel insertion was 3.18 mu g/mL in the dexmedetomidine group and 6.75 mu g/mL in the control group (p < 0.001). The incidence of hypotension (MBP < 80 % of the baseline) during the peri-insertion period of i-gel was higher in the control group (p = 0.001), whereas the incidence of bradycardia (HR < 80 % of the baseline) was higher in the dexmedetomidine group (p = 0.001).

Preoperative dexmedetomidine reduced the EC50 of propofol for successful i-gel insertion without muscle relaxants.