BACKGROUND The ability of current depth-of-anaesthesia monitors to differentiate subtle changes in the conscious state has not been well characterised. We examine the variability in bispectral index (BIS) scores associated with disconnected conscious and unconscious states as confirmed by a novel serial awakening paradigm. METHODS Seventy adult participants, given propofol or dexmedetomidine, had a cumulative 1381 electroencephalographic (EEG) recordings across two centres. Participants were awakened periodically, and their recent conscious experience interrogated by structured questioning. BIS were reconstructed from EEG using openibis, and the distribution of BIS scores were compared using linear mixed effects modelling. The predictive capacity of BIS across states of consciousness was also examined. RESULTS Reconstructed BIS scores correlated significantly with blood concentrations of propofol and dexmedetomidine (all P<0.001). However, while the average BIS was different between baseline wakefulness (mean BIS=95.1 [standard deviation=3.5]); connected consciousness with drug present (84.0 [10.9]); disconnected consciousness (70.0 [16.9]); and unconsciousness (68.1 [16.1]), the interquartile range of these states (3.6, 15.1, 23.3 and 26.8, respectively) indicated high degrees of overlap and individual variability. Connected consciousness could be differentiated from either disconnected consciousness or unconsciousness with 86% accuracy (i.e. 14% error rate), and disconnected consciousness differentiated from unconsciousness with 74% accuracy. CONCLUSIONS These results agree with previous studies that BIS scores fail to reliably differentiate between states of consciousness, exacerbated by segregating connected, disconnected, and unconscious states. To develop a method that reliably identifies the conscious state of an individual (not an average), work is needed to establish the causal mechanisms of disconnection and unconsciousness.

中文翻译：

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双频指数值与意识状态的关系：两项志愿者队列研究的分析。


背景 目前的麻醉深度监测仪区分意识状态细微变化的能力尚未得到很好的表征。我们检查了与断开连接的有意识和无意识状态相关的双频指数 （BIS） 评分的变异性，这被一种新的连续觉醒范式所证实。方法 70 名成年参与者，给予异丙酚或右美托咪定，在两个中心累积了 1381 次脑电图 （EEG） 记录。参与者会定期被唤醒，他们最近的意识经历会通过结构化的提问来询问。使用 openibis 从 EEG 重建 BIS，并使用线性混合效应模型比较 BIS 分数的分布。还检查了 BIS 对意识状态的预测能力。结果 重建的 BIS 评分与异丙酚和右美托咪定的血药浓度显著相关 （均 P<0.001）。然而，虽然基线觉醒度之间的平均 BIS 不同（平均 BIS=95.1 [标准差=3.5]）;与存在药物的意识相连 （84.0 [10.9]）;意识断开 （70.0 [16.9]）;和无意识 （68.1 [16.1]），这些状态的四分位距 （分别为 3.6、15.1、23.3 和 26.8） 表明高度重叠和个体变异性。连接意识可以以 86% 的准确率（即 14% 的错误率）与断开连接的意识或无意识区分开来，以 74% 的准确率区分断开连接的意识与无意识的区分。结论 这些结果与以前的研究一致，即 BIS 分数无法可靠地区分意识状态，分离连接、断开和无意识状态加剧了这种情况。 为了开发一种能够可靠地识别个人意识状态（而不是平均值）的方法，需要努力建立断开连接和无意识的因果机制。