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不同浓度异丙酚镇静时患者听觉稳态诱发反应指数的变化及其临床意义
时间：2010-08-24 09:09:23 来源： 作者：
【摘要】 目的 评价听觉稳态诱发反应(ASSR) 指数对异丙酚镇静深度的监测作用。方法 对30 例美国麻醉医师协会病情估计分级(ASA) 为Ⅰ～Ⅱ级的择期手术病人,通过计算机靶控输注系统(TCI) 经静脉输入异丙酚。按顺序维持4 种目标浓度:0.5μg/ ml 、1.0μg/ ml 、1.5μg/ ml 及2.0μg/ ml ,待效应室浓度与血浆浓度平衡2 min 后记录40 Hz ASSR 曲线,并依照OAA/ S 评分表判断病人的镇静深度。停止输注异丙酚,待病人对正常语调呼唤睁眼有反应时再次记录40 Hz ASSR 曲线。ASSR 指数的计算方法为ASSR 波上每隔5 ms 的两点波幅绝对差值的平方根之和。结果 Pa、Pb 波幅及ASSR 指数与目标浓度呈现良好的剂量相关性,相关系数分别为r = 0.780 , r = 0.826 , r = 0.759 , P < 0.01 ,它们相应的回归方程分别为Pa = - 0.354 ×目标浓度+ 1.018 , Pb = - 0.468 ×目标浓度+ 1.247 , ASSR 指数= - 2.924 ×目标浓度+ 11.78 ;ASSR 指数可准确反应Pa、Pb 波幅的变化,尤其与Pa 存在更好的相关性,相关系数分别为r = 0.811 和r = 0.735 , P < 0.01 ;ASSR 指数与病人镇静深度(OAA/ S 评分) 存在良好的相关性,相关系数为r = 0.815 , P < 0.01 ;病人由嗜睡状态转入睡眠状态时,Pa 波幅由0.88μv降低到0.60μv , ASSR 指数由10.52 降低到8.58 ,两者的降低均有显著意义, P < 0.05。本实验中ASSR指数降低到8.5 左右时病人即可能入睡,而意识消失需ASSR 指数下降到5.6 以下。结论ASSR 指数可用于监测异丙酚镇静深度的变化。与传统观测Pa、Pb 波幅的方法相比较,ASSR 指数具有可靠、简便的优点。 【关键词】 诱发电位,听觉; 二异丙酚; 麻醉 Indexes of auditory steady state response initiated by propofol of different concentrations 【Abstract】 Objective To assess the usefulness of auditory steady state response index (ASSR index) in monitoring the depth of sedation with propofol. Methods Propofol at the target plasma concentrations of 0. 5 , 1.0 ,1. 5 and 2. 0μg/ ml respectively was administered to 30 ASA grade Ⅰ～Ⅱadult patients to be operated on by computer controlled infusion technique. Two minutes after equilibration of the effect compartment′s concentration electively the plasma propofol concentration , the 40 Hz ASSR was recorded immediately at every concentration. Then the infusion was discontinued. When the patients opened their eyes to verbal commands of normal intonation , the 40 Hz ASSR was recorded again. The ASSR index was calculated as the sum of the square root of the absolute difference between every two successive 0. 5 ms segments of the auditory steady state response′s waveform. Thelevel of sedation was determined by the observer′s assessment based on the alertness/ sedation scale (OAA/ S) . The OAA/ S score of 2 or less was considered unconscious. Result The amplitudes of Pa and Pb waves and the ASSR index were linearly decreasing with the increase of propofol target concentration and the deepening of level of sedation dose-dependently with the association coefficients as r = 0. 780 , r = 0. 826 , and r = 0. 759 respectively ,P < 0.01. The corresponding regression equations are as follows : Pa = - 0. 354×target concentration + 1. 018 ,and Pb = - 0. 468 ×target concentration + 1. 247 , ASSR index = - 2. 924 ×target concentration + 11. 78. The ASSR index reflected the amplitudes of Pa and Pb , especially the amplitude of Pa ( r = 0. 811 and 0. 735 respectively , P < 0. 01) . In addition , ASSR index was correlated with the depth of patient′s sedation ( r = 0. 815 ,P < 0. 01) . When the patients fell asleep from drowsy state , the amplitude of Pa decreased from 0. 9μv to 0. 6μv , and the ASSR index decreased from 10. 5 to 8. 6 with statistical significance ( P < 0. 05) . The patients would not fall asleep until the ASSR index reduced to about 8. 5 , while reliable unconsciousness happened only when the ASSR index was lowerthan5.6. Conclusion ASSR index is useful in monitoring the depth of sedation with propofol. Compared with the amplitudes of Pa and Pb observed traditionally , ASSR index is more accurate and simple and convenient. 【Key words】 Evoked potentials ,auditory ; Propofol ; Anesthesia 为了将40 Hz 听觉稳态诱发反应(40 Hz ASSR)波形中所含的信息综合指数化,以达到类似脑电双频指数(BIS) 一目了然的直观效果,本研究中我们将40 Hz 听觉稳态诱发反应的波形综合量化,提出了听觉稳态诱发反应(ASSR) 指数的概念。并运用靶控输注(target controlled infusion , TCI) 技术,通过对不同异丙酚目标浓度下40 Hz ASSR 变化的比较,探讨其临床意义。 对象与方法 1. 对象: 美国麻醉医师协会病情估计分级(ASA) 为Ⅰ～Ⅱ级的病人30 例,男13 例,女17 例。年龄35 岁±13 岁,体重60 kg±11 kg ,拟在全身麻醉下行鼻内窥镜择期手术。既往均无大量镇静催眠药物使用史,有听力障碍、精神、神经疾患史及心肺、肝肾功能障碍的病人被排除在外。 2. 靶控输注(TCI) 系统:由Intel 486 计算机与佳士比3500 电脑注射泵和计算机与注射泵的接口组成。计算机控制软件为stelpump version 1.05 。程序采用Jacobs 等根据三室药代动力学模型、以效应室浓度为靶控目标的计算方法,药代动力学参数选用Tackley 等[2 ]提出的参数。 3.40 Hz 听觉稳态诱发反应的测定:仪器采用美国Nicolet 公司生产Spirit 听觉电生理测试系统。刺激声:500 Hz 短纯音(tone burst) ,升/ 降平台时间为2-1-2周期; 刺激强度: 80dBnHL ,经耳机左耳给声;刺激重复率:39.1 次/ s ;扫描时间:100 ms ; 叠加次数:500 次;带通滤波:5～100 Hz ;电极放置:3 枚银质盘形电极分别固定于国际标准脑电检测电极区的At1 (左耳乳突,参考电极) 、At2 (右耳乳突,接地电极) 、FPz 区位(前额,记录电极) ;极间阻抗: < 5 KΩ;环境噪声:40～50 dB。 4.ASSR 指数的计算方法:记录到的40 Hz 听觉稳态诱发反应的波形存于软盘中用于前两个正相波Pa 和Pb 波幅的测定及ASSR 指数的计算。ASSR 指数的计算方法为ASSR 波上每隔5 ms 的两点波幅绝对差值的平方根之和。 5.实验方法:病人术前常规禁食水8 h ,入手术室前30 min 肌肉注射阿托品0.5 mg。实验过程及目的均征得病人同意。入室后开放静脉通路,输入乳酸钠林格液500 ml/ h。平静休息10 min 后,记录平均动脉压(MAP) 、脉搏血氧饱和度(SpO2) 及心率(HR) ,同时获得40 Hz ASSR 波作为基础对照。利用目标浓度控制输注系统(TCI) 经一侧前臂静脉输入异丙酚,目标浓度依次设定为0.5、1.0、1.5 及2.0μg/ ml ,每一浓度均待血浆浓度与效应室浓度平衡2min 后,记录ASSR 波形及各观察指标。每次记录前均呼唤病人睁眼或推动其肩膀令其睁眼,以判断其镇静深度。镇静深度的判断参照OAA/ S 评分表[3 ] 。呼唤时病人可睁眼认为有意识存在,否则为意识消失(OAA/ S 评分2 分或以下) [4 ] 。为维持正常的SpO2 (大于95 %) ,必要时人工托下颌保持气道通畅并予以吸氧。停止输注异丙酚,待病人对正常语调呼唤睁眼有反应(OAA/ S 评分4 分) 时再次记录各观察值。实验结束后即刻进行麻醉诱导及插管。 参考文献 1 Jacobs JR , Williams EA. 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