The Effects Of Different Doses Of Dexmedetomidine On The MAC Of Sevoiflurane In Adults With Laryngeal Mask Stimulus

Objective:To observe the effects of different doses of dexmedetomidine(DEX)on the minimum alveolar concentration(MAC)of sevoflurane in adults with laryngeal mask airway(LMA)stimulus.Methods:Seventy-five patients with American Society of Anesthesiologists(ASA)physical status Ⅰ-Ⅱ grade,aged 20-60 years,undergoing elective laryngeal mask general anesthesia for upper extremity fracture surgery,hernia repair,and laparoscopic cholecystectomy with an estimated time of 1-2 hours,were randomly assigned to three groups with different dexmedetomidine infusion doses(25 cases in each group):group D0(DEX 0μg/kg),group D1(DEX 0.5μg/kg),and group D2(DEX 1.0 μg/kg).All patients were not given preoperative medication.The electrocardiogram,pulse oxygen saturation,non-invasive blood pressure and brain electricity bispectral(BIS)index were routinely monitored before induction of anesthesia.The three groups were infused dexmedetomidine according to above doses in 10 minutes before induction,respectively.A high-concentration vital capacity method was applied to induction by inhalation of 8%sevoflurane and pure oxygen(6L/min).After patient’s eyelash reflection had disappeared,the end-expiratory concentration of sevoflurane was adjusted to a predetermined value and maintained stable for at least 15 minutes,then a laryngeal mask airway was inserted.The patient’s response to laryngeal mask airway insertion was observed for 30 seconds.If the patient appeared limb movements,coughing,incomplete mouth opening and jaw looseness,and biting laryngeal mask,a positive reaction was considered;on the contrary,a negative reaction was considered.An up and down and sequential method was used to determine the MACLMA value of sevoflurane in each group when the laryngeal mask airway was inserted.The concentration gradient of sevoflurane was 0.2%.The relationship between the MAC of sevoflurane in adults with the stimulus of laryngeal masks and the dose of dexmedetomidine was evaluated by curvilinear regression.Results:The MACLMA values of sevoflurane required for successful insertion of adult laryngeal mask airway in groups D0,D1 and D2were(2.93±0.25)%,(2.53±0.13)%,and(1.93±0.21)%,respectively.Dexmedetomidine with a dose of 0.5 μg/kg and 1.0 μg/kg can reduce the MACLMA value of sevoflurane by 14%and 34%,respectively.The curvilinear regression equation of the interaction between sevoflurane MACLMAand the dose of dexmedetomidine was y=2.930-0.6x-0.4x2,R2=1.Conclusion:Dexmedetomidine can effectively reduce the MACLMA value of sevoflurane required for laryngeal mask airway insertion in adults.