目的 比较右美托咪定与丙泊酚应用于小儿MRI下脑立体定向中的有效性与安全性。方法 100例术前需在基础麻醉下行MRI脑立体定向的患儿，随机分为两组，右美托咪定组(组Ⅰ)和丙泊酚组(组Ⅱ)。患儿入手术室后缓慢静脉注射氯胺酮1~2 mg/kg，同时组Ⅰ以右美托咪定1.0 μg/(kg·h)维持，组Ⅱ以丙泊酚6 mg/(kg·h)维持，给氯胺酮并入睡后安放立体定向仪头架，入磁共振室前停用维持量的输注，出磁共振室后护送回手术室进行手术，检查过程中必要时单次追加丙泊酚。记录两组患儿多个时间点MBP、HR和SPO₂的变化，并记录各组需要单次追加丙泊酚的病例数、苏醒时间以及呼吸抑制、过早苏醒、检查后躁动等不良反应的发生率。结果 组Ⅰ中有1例需要追加丙泊酚，无呼吸抑制和需要吸氧的病例;组Ⅱ中有13例需追加丙泊酚，16例发生呼吸抑制，其中11例需要吸氧改善SPO₂，与组Ⅰ比较差异有统计学意义(P<0.01);组Ⅰ心率有所下降(P<0.05)，但仍在正常范围内。结论 在小儿MRI下脑立体定向检查的过程中，右美托咪定维持组不但可以明显减少追加丙泊酚的次数，还可保证患儿在检查全程安静不动，且无呼吸抑制。

Objective To evaluate the efficacy and safety of administration of dexmedetomidine and propofol in pediatric patients who need a preoperative stereotaxis procedure using magnetic resonance imaging (MRI). Methods 100 pediatric patients needing stereotaxic check by MRI under basic anesthesia were randomly divided into two groups. All subjects were given ketamine 1-2 mg/kg to get thorough sedation. The maintenance dose of dexmedetomidine in group Ⅰwas 1.0 μg/(kg·h), and propofol in group Ⅱwas 6 mg/(kg·h). After they fell asleep, all subjects were given local anesthesia to put on the stereotaxic instrument. Patients’ MBP, HR and SPO₂ were recorded at several necessary time points . Patients who needed additional propofol and patients’ recovery time were recored. Additionally, we also observed the incidence of adverse events such as respiratory depression, unexpected early recovery and postoperative agitation. Results Compaired with group Ⅰ,the cases who needed additional propofol and the subjects who had respiratory depression were significantly increased in group Ⅱ (P<0.01 ). The heart rate dropped somewhat during the checking time in group Ⅰ, but still within the normal range (P>0.05). There was no significant difference in postoperative recovery status between these two groups. Conclusions During stereotaxic checking period by MRI in pediatric patients, the maintenance dose 1 μk/(kg·h) of dexmedetomidine after a loading dose of ketamine 1-2 mg/kg can not only reduce the additional injection of propofol, but also ensure the children’s quietness and safety without respiratory depression.