Effect Of Dexmedetomidine On Median Effective Concentration Of Propofol Required For Pediatric Laryngeal Mask Insertion

Objective:To evaluate the median effective concentration(EC50)of propofol requiring for pediatric laryngeal mask airway(LMA)insertion when combined with dexmedetomidine.Methods:Twenty-nine ASA physical status?patients,aged 6-11 yr,weighting 20-50 kg,scheduled for elective urinary surgery under general anesthesia,were divided into 2 groups,propofol group(group P,n=17)and dexmeditomidine+propofol group(group D,n=12).EC50 of propofol was determined by modified Dixon's up-and-down sequential experiment.Anesthesia were induced with target-controlled propofol by TCI in group P,the initial target-controlled concentration was 3 ?g/ml,and the increments or decrements was 0.2?g/ml.The LMA were inserted when the target effect-site concentration and the plasma concentration reached the balanced.Dexmeditomidine 0.5 ?g/kg in normal saline were infused over 10 min in group D.And then,propofol was given as group P,the initial target-controlled concentration was 3 ?g/ml.Swallowing,coughing,,biting LMA and body movement were defined as the positive response of LMA insertion.When the response to LMA insertion was positive,the concentration of propofol increased 0.2 ?g/ml in the next patient,and when the response was negative,the concentration of propofol decreased 0.2 ?g/ml in the next patient.When three wave rest and trough were deserved,the test was finished.Observe and record HR and NIBP on T0(into the operating room)? T1(before propofol infusion)?T2(after propofol infusion)and T3(after LMA insertion).The occurrence of positive response under different plasma concentration.EC50 and the 95%CI of propofol required for inhibition of pediatric LMA insertion were calculated.Results:1 There was no difference between the two groups in general situation(P>0.05).2 The EC50 of propofol for inhibition of the response to pediatric LMA insertion in group P was 4.51(4.43~4.59)? g/ml.3 When combined with dexmedetomidine,the EC50 of.propofol for inhibition of the response to pediatric LMA insertion in group D was 2.31(2.24~2.39)?g/ml.4 Compare to group P,EC50 and 95%CI were decreased in group D(P<0.05).Conclusion:Dexmedetomidine applied in pediatric LMA insertion can decrease the effect-site concentration of propofol.When combined with 0.5 ?g/kg dexmeditomidine,the EC50(95%CI)of propofol for inhibition of pediatric LMA insertion is 2.31(2.24~2.39)?g/ml.