目的 观察不同剂量米库氯铵在不同年龄段患儿麻醉中的肌松时效。方法 择期手术患儿60例，美国麻醉师协会（ASA）评级为Ⅰ或Ⅱ级。按年龄分为婴幼儿组（≤3岁，Ⅰ组）和年长儿组（＞3岁，Ⅱ组），再根据米库氯铵首次剂量（0.2、0.25 mg/kg）每组随机分为2个亚组，分别为Ⅰ0.2、Ⅰ0.25组和Ⅱ0.2、Ⅱ0.25组，每组15例。当肌颤搐反应恢复至25%时，间断静脉注射米库氯铵0.1 mg/kg维持肌松。采用TOF-Watch SX加速度肌松监测仪连续监测尺神经4个成串刺激的反应（TOF）。观察并记录肌松时效指标。结果 Ⅰ0.25组肌松起效快于Ⅰ0.2、Ⅱ0.25组，Ⅱ0.25组起效快于Ⅱ0.2组，差异均有统计学意义（P<0.05）。各组间首次静脉注射及多次追加米库氯铵的临床作用时间、末次追加米库氯铵的恢复指数、第4个肌颤搐与第1个肌颤搐的比值（TOFR）恢复至0.75和0.9时间的差异均无统计学意义（P>0.05）。结论 米库氯铵在婴幼儿起效快于年长儿，0.25 mg/kg起效快于0.2 mg/kg；神经肌肉功能的恢复与患儿的年龄和追加次数无关。

Objective To evaluate the neuromuscular blockade of different doses of mivacurium in pediatric anesthesia. Methods Sixty children with American Society of Anesthesiologists （ASA） class Ⅰor Ⅱ undergoing selective surgery were randomly allocated to groupⅠ(≤3 years old) and groupⅡ (＞3 years old). Each group was subdivided according to the initial dosage of mivacurium (0.2 mg/kg or 0.25mg/kg)(groupⅠ0.2, group Ⅱ0.2, group Ⅰ0.25 and group Ⅱ0.25，n=15). At twitch recovery to 25%, neuromuscular blockade was maintained by intermittent intravenous injection of 0.1 mg/kg mivacurium. Response of ulnar nerve to train-of-four (TOF) stimulation was monitored with TOF-Watch SX muscle relaxation monitor, and the neuromuscular blockade indexes were recorded. Results The onset time in group Ⅰ0.25 was significantly shorter than that in group Ⅰ0.2 and group Ⅱ0.25（P<0.05）, and the onset time in group Ⅱ0.25 was significantly shorter than that in group Ⅱ0.2 (P<0.05). There was no significant difference in the duration of clinical action of initial dose and repeated dose of mivacurium among groups (P>0.05). There was no difference in the recovery index and duration of TOF ratio (TOFR) recovery to 0.75 and 0.9 of the last dose of mivacurium among groups (P>0.05). Conclusion Children younger than 3 years old have shorter onset time than elder ones, and 0.25 mg/kg mivacurium may produce shorter onset time than 0.2 mg/kg mivacurium. Neuromuscular recovery is independent of age and times of additional doses.