Schneider G, Gelb A W, Schmeller B, Tschakert R, Kochs E
Department of Anaesthesiology, Klinikum rechts der Isar, Technische Universität München, Ismaningerstrasse 22, D-81675 Munich, Germany.
Br J Anaesth. 2003 Sep;91(3):329-35. doi: 10.1093/bja/aeg188.
Patient state index (PSI) and bispectral index (BIS) are values derived from the EEG, which can measure the hypnotic component of anaesthesia. We measured the ability of PSI and BIS to distinguish consciousness from unconsciousness during induction and emergence from anaesthesia and a period of awareness in surgical patients.
Forty unpremedicated patients were randomized to receive: (1) sevoflurane/remifentanil (< or =0.1 microg kg(-1) min(-1)), (2) sevoflurane/remifentanil (> or = 0.2 microg kg(-1) min(-1)), (3) propofol/remifentanil (< or =0.1 microg kg(-1) min(-1)), (4) propofol/remifentanil (> or = 0.2 microg kg(-1) min(-1)). Every 30 s after the start of the remifentanil, patients were asked to squeeze the investigator's hand. Sevoflurane or propofol were given until loss of consciousness (LOC1). Tunstall's isolated forearm technique was used during neuromuscular block with succinylcholine. After tracheal intubation, propofol or sevoflurane were stopped until return of consciousness (ROC1). Propofol or sevoflurane were re-started to induce LOC2. After surgery, drugs were discontinued and recovery (ROC2) was observed. PSI and BIS at LOC (LOC1 and LOC2) were compared with those at ROC (ROC1 and ROC2) (t-test). Prediction probability (P(k)) was calculated from values at the last command before and at LOC and ROC. Values are mean (SD).
At non-responsiveness, BIS (66 (17)) and PSI (55 (23)) were significantly less than at responsiveness (BIS, 79 (14); PSI, 77 (18); P<0.05). The wide variation with both BIS and PSI measurements of the 80 'awareness' values led to an erroneous classification as unconscious in some cases (BIS, six patients; PSI, nine patients). P(k) was 0.68 (0.03) (BIS) and 0.69 (0.03) (PSI).
Despite significant differences between mean values at responsiveness and non-responsiveness for BIS and PSI, neither measure may be sufficient to detect awareness in an individual patient, reflected by a P(k) less than below 70%.
患者状态指数（PSI）和脑电双频指数（BIS）是从脑电图得出的值，可测量麻醉的催眠成分。我们测量了PSI和BIS在麻醉诱导期、苏醒期以及手术患者的一段知晓期内区分意识与无意识状态的能力。
40例未用术前药的患者被随机分为四组，分别接受：（1）七氟烷/瑞芬太尼（≤0.1微克·千克⁻¹·分钟⁻¹）；（2）七氟烷/瑞芬太尼（≥0.2微克·千克⁻¹·分钟⁻¹）；（3）丙泊酚/瑞芬太尼（≤0.1微克·千克⁻¹·分钟⁻¹）；（4）丙泊酚/瑞芬太尼（≥0.2微克·千克⁻¹·分钟⁻¹）。瑞芬太尼开始输注后每30秒，要求患者挤压研究者的手。给予七氟烷或丙泊酚直至意识消失（LOC1）。在使用琥珀酰胆碱进行神经肌肉阻滞期间采用滕斯托尔孤立前臂技术。气管插管后，停用丙泊酚或七氟烷直至意识恢复（ROC1）。重新开始输注丙泊酚或七氟烷以诱导第二次意识消失（LOC2）。术后，停用药物并观察苏醒情况（ROC2）。比较意识消失时（LOC1和LOC2）与意识恢复时（ROC1和ROC2）的PSI和BIS（t检验）。根据最后指令前、意识消失时和意识恢复时的值计算预测概率（P(k)）。数据以均值（标准差）表示。
在无反应状态时，BIS（66（17））和PSI（55（23））显著低于有反应状态时（BIS，79（14）；PSI，77（18）；P<0.05）。80个“知晓”值的BIS和PSI测量值变化很大，导致在某些情况下被错误分类为无意识（BIS，6例患者；PSI，9例患者）。P(k)为0.68（0.03）（BIS）和0.69（0.03）（PSI）。
尽管BIS和PSI在有反应和无反应状态时的均值存在显著差异，但两种测量方法可能都不足以检测个体患者的知晓情况，这表现为P(k)低于70%。
