Glass P S, Bloom M, Kearse L, Rosow C, Sebel P, Manberg P
Department of Anesthesiology, Duke University, Durham, North Carolina 27710, USA.
Anesthesiology. 1997 Apr;86(4):836-47. doi: 10.1097/00000542-199704000-00014.
The bispectral index (BIS), a value derived from the electroencephalograph (EEG), has been proposed as a measure of anesthetic effect. To establish its utility for this purpose, it is important to determine the relation among BIS, measured drug concentration, and increasing levels of sedation. This study was designed to evaluate this relation for four commonly used anesthetic drugs: propofol, midazolam, isoflurane, and alfentanil.
Seventy-two consenting volunteers were studied at four institutions. Volunteers were given either isoflurane, propofol, midazolam, or alfentanil. Each volunteer was administered a dose-ranging sequence of one of the study drugs to achieve predetermined target concentrations. A frontal montage was used for continuous recording of the EEG. At each pseudo-steady-state drug concentration, a BIS score was recorded, the participant was shown either a picture or given a word to recall, an arterial blood sample was obtained for subsequent analysis of drug concentration, and the participant was evaluated for level of sedation as determined by the responsiveness portion of the observer's assessment of the alertness/ sedation scale (OAAS). An OAAS score of 2 or less was considered unconscious. The BIS (version 2.5) score was recorded in real-time and the BIS (version 3.0) was subsequently derived off-line from the recorded raw EEG data. The relation among BIS, measured drug concentration, responsiveness score, and presence or absence of recall was determined by linear and logistic regression for both the individual drugs and, when appropriate, for the pooled results. The prediction probability was also calculated.
The BIS score (r = 0.883) correlated significantly better than the measured propofol concentration (r = -0.778; P < 0.05) with the responsiveness score. The BIS provided as effective correlation with responsiveness score of the OAAS as did the measured concentration for midazolam and isoflurane. None of the volunteers given alfentanil lost consciousness and thus were excluded from the pooled analysis. The pooled BIS values at which 50% and 95% of participants were unconscious were 67 and 50, respectively. The prediction probability values for BIS ranged from 0.885-0.976, indicating a very high predictive performance for correctly indicating probability of loss of consciousness.
The BIS both correlated well with the level of responsiveness and provided an excellent prediction of the loss of consciousness. These results imply that BIS may be a valuable monitor of the level of sedation and loss of consciousness for propofol, midazolam, and isoflurane.
脑电双频指数（BIS）是从脑电图（EEG）得出的值，已被提议作为麻醉效果的一种衡量指标。为确定其在此方面的效用，确定BIS、测得的药物浓度以及不断加深的镇静水平之间的关系很重要。本研究旨在评估四种常用麻醉药物（丙泊酚、咪达唑仑、异氟烷和阿芬太尼）的这种关系。
在四个机构对72名同意参与的志愿者进行了研究。给志愿者使用异氟烷、丙泊酚、咪达唑仑或阿芬太尼中的一种。给每位志愿者给予一种研究药物的剂量递增序列，以达到预定的目标浓度。采用额部导联连续记录脑电图。在每个伪稳态药物浓度下，记录BIS评分，向参与者展示一张图片或给出一个单词让其回忆，采集动脉血样用于后续药物浓度分析，并根据观察者对警觉/镇静量表（OAAS）的反应部分评估参与者的镇静水平。OAAS评分为2或更低被认为是无意识状态。实时记录BIS（2.5版）评分，随后从记录的原始脑电图数据离线得出BIS（3.0版）。通过线性和逻辑回归确定个体药物以及在适当情况下汇总结果时BIS、测得的药物浓度、反应评分以及是否能回忆之间的关系。还计算了预测概率。
BIS评分（r = 0.883）与反应评分的相关性显著优于测得的丙泊酚浓度（r = -0.778；P < 0.05）。BIS与OAAS反应评分的相关性与咪达唑仑和异氟烷测得的浓度一样有效。接受阿芬太尼的志愿者均未失去意识，因此被排除在汇总分析之外。50%和95%的参与者失去意识时的汇总BIS值分别为67和50。BIS的预测概率值范围为0.885 - 0.976，表明在正确指示意识丧失概率方面具有非常高的预测性能。
BIS与反应水平相关性良好，并能出色地预测意识丧失。这些结果表明，BIS可能是丙泊酚、咪达唑仑和异氟烷镇静水平和意识丧失的有价值监测指标。
