利多卡因表面麻醉下七氟烷抑制全麻患儿喉罩拔除反应的最低肺泡有效浓度观察

Minimum Alveolar Concentration of Sevoflurane for Laryngeal Mask Airway Removal in Anesthetized Children under Topical anesthesia of Lidocaine

目的观察在利多卡因咽喉部表面麻醉下七氟烷抑制全麻患儿喉罩拔除反应的最低肺泡有效浓度（ED_（50））。方法选取28例短小手术全麻患儿,患儿入室后给予七氟烷和纯氧诱导,2%利多卡因凝胶涂抹于喉罩罩杯的两面,斜方肌挤压反应消失后,置入喉罩,手术结束后维持预设呼气末七氟烷浓度10分钟,采用序贯法调整七氟烷浓度,起始呼气末七氟烷浓度1.4%,相邻浓度差为0.2%。喉罩拔除成功,则下1例患儿降低1个浓度梯度;喉罩拔除失败,则下1例升高1个浓度梯度。拔除喉罩前或拔除喉罩过程中没有出现有目的的肢体运动、屏气、咳嗽、喉痉挛和低氧血症等为喉罩拔除成功,否则为失败。结果 28例患儿手术时间为（18±9）分钟,喉罩留置时间（29±10）分钟。根据Dixon测得七氟烷ED50为（0.78±0.22）%,概率回归分析患儿成功喉罩拔除七氟烷ED_（50）和95%有效量（ED_（95））分别为0.77%[95%可信区间（0.65%～0.95%）]和1.09%[95%可信区间（0.92%～1.35%）]。结论通过咽喉部利多卡因表面麻醉,患儿在浅麻醉比较耐受喉罩通气道,明显降低喉罩通气道拔除的七氟烷ED_（50）和ED_（95）,能降低拔除喉罩期间发生呼吸道并发症的风险。

Objective To determine the optimal minimum alveolar concentration（ ED_（50）） of sevoflurane that blunt responses to removal of laryngeal mask airway（ LMA） in anesthetized children under laryngeal topical anesthesia of lidocaine gel. Method Twenty eight children undergoing minor elective surgery scheduled for general anesthesia were enrolled in this study. The LMA with lidocaine gel applied was inserted after a trapezius squeeze test（ the end- tidal concentration of sevoflurane was maintained at the predetermined level for ten minutes after surgery,that was determined by the Dixon up and down method,with 1. 4% as the initial level and 0. 2% as a step. the end- tidal concentration of sevoflurane was increased / decreased by 0. 2% in the next patient if LMA removal was success or failure. The successful removal was defined as absence of the development of gross purposeful limb movements,breath-holding,laryngospasm or hypoxia. Result Twenty eight children was included,duration of surgery was（18 ± 9） minutes,duration of laryngeal mask airway placement（29 ± 10） minutes. ED_（50） of sevoflurane was（0. 78 ± 0. 22） % using Dixon equation,and from probit regression analysis,ED50 and ED95of sevoflurane for successful removal of LMA in anesthetized children were 0. 77%[95% confidence limits（0. 65% ～ 0. 95%）],1. 09%[95% confidence limits（0. 92% ～ 1. 35%）] respectively. Conclusion laryngeal topical anesthesia of lidocaine allow high toleration for LMA in light anesthesia state,decrease ED50 and ED_（95） of sevoflurane for successful removal of LMA and reduce risk of respiratory complication during removal of LMA in children.