右美托咪定与咪达唑仑对老年患者呼吸抑制时异丙酚EC_(50)的影响

目的研究右美托咪定与咪达唑仑对老年患者呼吸抑制时异丙酚的半数有效浓度(EC50)的影响。方法选择硬膜外麻醉下行下肢手术的老年患者,年龄65⁸0岁,性别不限,ASAⅠ80岁,性别不限,ASAⅠ^Ⅱ级,随机分为三组,D组、M组和C组分别静脉泵注右美托咪定0.4μg/kg、咪达唑仑0.03 mg/kg和生理盐水。之后开启靶控输注(TCI)异丙酚,D组、M组和C组第1例患者的血浆靶浓度分别设定为1.4μg/ml、1.2μg/ml和2.2μg/ml。根据呼吸抑制的发生情况确定下1例血浆靶浓度,相邻靶浓度的比值为1.1。计算出三组异丙酚TCI时患者呼吸抑制的EC50。结果 D组、M组和C组呼吸抑制时异丙酚EC50分别为1.64μg/ml(95%可信区间为1.52Ⅱ级,随机分为三组,D组、M组和C组分别静脉泵注右美托咪定0.4μg/kg、咪达唑仑0.03 mg/kg和生理盐水。之后开启靶控输注(TCI)异丙酚,D组、M组和C组第1例患者的血浆靶浓度分别设定为1.4μg/ml、1.2μg/ml和2.2μg/ml。根据呼吸抑制的发生情况确定下1例血浆靶浓度,相邻靶浓度的比值为1.1。计算出三组异丙酚TCI时患者呼吸抑制的EC50。结果 D组、M组和C组呼吸抑制时异丙酚EC50分别为1.64μg/ml(95%可信区间为1.52¹.78μg/ml)、1.18μg/ml(95%可信区间为1.151.78μg/ml)、1.18μg/ml(95%可信区间为1.15¹.21μg/ml)和2.35μg/ml(95%可信区间为2.191.21μg/ml)和2.35μg/ml(95%可信区间为2.19².51μg/ml)。D组、M组的EC50明显低于C组,M组低于D组。结论右美托咪定和咪达唑仑均能降低老年患者呼吸抑制时异丙酚的EC50,右美托咪定降低异丙酚的EC50的幅度显著小于咪达唑仑。

Effect of dexmedetomidine and midazolam on median effective concentration of propofol for respiratory depression in aged patients

Objective To investigate dexmedetomidine and midazolam for the effect on the median effective concentration（EC50） of propofol for respiratory depression in aged patients. Methods ASAⅠor Ⅱgrade patients, aged 65-80 years, scheduled for lower limb surgery under epidural anesthesia were randomly allocated to 3 groups： group D received 0.4 μg/kg dexmedetomidine, group M received 0.03mg/kg midazolam and group C received 10 ml sodium chloride. The propofol TCI was started after infusing the experimental medicine. The target plasma concentration of the first patient in group D was set to 1.4 μg/ml, 1.2 μg/ml in group M and 2.2 μg/ml in group C. The following patient＇s target plasma concentration was determined based on the reaction of respiratory depression in the previous patient. The ratio of the adjacent target concentration was 1.1. Results EC50 of propofol TCI for respiratory depression was 1.64 μg/ml（95% CI was 1.52-1.78 μg/ml） in group D, 1.18 μg/ml（95% CI was 1.15- 1.21 μg/ml） in group M and 2.35 μg/ml（95% CI was 2.19-2.51 μg/ml） in group C. The EC50 was lower in group D and M than that in group C, and it was lower in group M than in group D. Conclusions Both dexmedetomidine and midazolam can decrease the EC50 of propofol TCI for respiratory depression in aged patients. The extent of reduction in the EC50 of propofol caused by dexmedetomidine is significantly smaller than midazolam.