A comparison of optimal concentrations of sevoflurane for insertion of the proseal laryngeal mask airway or classic laryngeal mask airway in children

Objective To quantify and compare the minimum alveolar concentration(MAC) of sevoflurane for insertion of the proseal laryngeal mask airway(PLMA) and classic laryngeal mask airway(CLMA) in children.Methods Fifty four ASA Ⅰ or Ⅱ children,aged 3 to 9 years old,undergoing surgery under general anesthesia,were randomly divided into 2 groups: the PLMA group(group P) and CLMA group(group C),with twenty seven cases in each group.General anesthesia was induced via mask with sevoflurane,and the PLMA or CLMA was inserted after a predetermined end-tidal sevoflurane concentration was maintained for at least 10 min.The end-tidal sevoflurane concentration was predetermined according to Dixon's up-down method,with 0.2% as a step size.The initial patients received 2.2% and 2.0% sevoflurane for group P and group C,respectively.The insertion conditions were noted as dissatisfactory when the jaw was not relaxed enough to allow for PLMA or CLMA insertion,or coughing,swallowing,movement of the limbs,breath holding,laryngospasm occurred within 1 min of insertion of PLMA or CLMA.The predetermined sevoflurane concentration and the satisfaction of insertion conditions for each child were recorded.Results The MAC of sevoflurane to achieve satisfying condition of the PLMA and CLMA insertion in 50% of children were(2.21±0.11)% and(1.99±0.11)%,respectively,and the difference was significant(P0.01).The ED95(95%CI) were 2.40%(2.28%-2.74%) and 2.14%(2.03%-2.44%) for the satisfying condition of the PLMA and CLMA insertion,respectively.Conclusion The MAC of sevoflurane to achieve satisfying insertion condition of the PLMA in 50% of children aged 3 to 9 yrs was higher than that of CLMA.