氯胺酮和依托咪酯的BIS_(50)及其对脑电双频指数的影响

The BIS_(50) of ketamine and etomidate and their effects on BIS

目的 分别测定氯胺酮和依托咪酯诱导时半数患者入睡时的脑电双频指数(BIS)即BIS_(50)和半数有效量(ED_(50)),比较他们对BIS的影响。方法 选择40例无服用精神药物和镇静催眠药、无术前用药的择期手术患者(ASA Ⅰ～Ⅱ级),随机分为氯胺酮组(K组,n=20)和依托咪酯组(E组,n=20),以半数效量序贯法分别进行氯胺酮和依托咪酯诱导的睡眠观察,以对语言指令不应和睫毛反射消失为入睡指标,同时记录BIS的变化。对取得的数据以直线回归的方法和加权均数法分别求得氯胺酮、依托咪酯的BIS_(50)和ED_(50)。结果 氯胺酮和依托咪酯诱导后,BIS明显下降(P=0.000983),但两者各自BIS下降幅度在入睡与未睡患者之间没有明显差异(P=0.920501和0.956263)。氯胺酮的BIS_(50)和ED_(50)分别是78.81(95％可信区间67.27～97.10)和0.757 mg/kg(95％可信区间0.535～1.071mg/kg),依托咪酯的BIS_(50)和ED_(50)分别是60.00(95％可信区间49.74～76.95)和0.089mg/kg(95％可信区间0.073～0.107mg/kg)。结论 氯胺酮和依托咪酯皆显著降低BIS,但仅凭BlS难以准确预计是否进入睡眠状态。

Objective To compare the effects of ketamine and etomidate on bispectral index (BIS) by determining their value of bispectral index and dosage at which 50% of patients falls into unconsciousness(BIS_(50) and ED_(50)) during induction. Methods Forty selective unpremedicated adult surgical patients(ASA Ⅰ-Ⅱ)without history of having any hypnotics and sedatives or psychiatric diseases were randomly allocated to one of two groups with 20 cases each. Ketamine was used for induction in group K and etomidate in group E. With sequential experimental method,a serial doses of ketamine or etomidate was given for the observation of loss of consciousness and changes in BIS. The loss of response to verbal command and eyelash stimulation was used as a standard identifying unconsciousness during BIS recording. The data were analyzed with linear regression and calculated with weighted averaging for obtaining BIS_(50) and ED_(50). Results Either ketamine or etomidate could markedly decrease BIS. However, there was no significant difference in BIS values between sleepers and nonsleepers between group K and E. The values of BIS_(50) and ED_(50) for ketamine were 78.81 and 0.757mg/kg and for etiomdate were 60.00 and 0.089 mg/kg respectively. Conclusion Both ketamine and etomidate decrease BIS significantly,but it is hard to predict the unconsciousness only by BIS. The value of BIS_(50) appears to be useful to judge the depth of unconsciousness.