Avidan Michael S, Zhang Lini, Burnside Beth A, Finkel Kevin J, Searleman Adam C, Selvidge Jacqueline A, Saager Leif, Turner Michelle S, Rao Srikar, Bottros Michael, Hantler Charles, Jacobsohn Eric, Evers Alex S
Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO 63110, USA.
N Engl J Med. 2008 Mar 13;358(11):1097-108. doi: 10.1056/NEJMoa0707361.
Awareness during anesthesia is a serious complication with potential long-term psychological consequences. Use of the bispectral index (BIS), developed from a processed electroencephalogram, has been reported to decrease the incidence of anesthesia awareness when the BIS value is maintained below 60. In this trial, we sought to determine whether a BIS-based protocol is better than a protocol based on a measurement of end-tidal anesthetic gas (ETAG) for decreasing anesthesia awareness in patients at high risk for this complication.
We randomly assigned 2000 patients to BIS-guided anesthesia (target BIS range, 40 to 60) or ETAG-guided anesthesia (target ETAG range, 0.7 to 1.3 minimum alveolar concentration [MAC]). Postoperatively, patients were assessed for anesthesia awareness at three intervals (0 to 24 hours, 24 to 72 hours, and 30 days after extubation).
We assessed 967 and 974 patients from the BIS and ETAG groups, respectively. Two cases of definite anesthesia awareness occurred in each group (absolute difference, 0%; 95% confidence interval [CI], -0.56 to 0.57%). The BIS value was greater than 60 in one case of definite anesthesia awareness, and the ETAG concentrations were less than 0.7 MAC in three cases. For all patients, the mean (+/-SD) time-averaged ETAG concentration was 0.81+/-0.25 MAC in the BIS group and 0.82+/-0.23 MAC in the ETAG group (P=0.10; 95% CI for the difference between the BIS and ETAG groups, -0.04 to 0.01 MAC).
We did not reproduce the results of previous studies that reported a lower incidence of anesthesia awareness with BIS monitoring, and the use of the BIS protocol was not associated with reduced administration of volatile anesthetic gases. Anesthesia awareness occurred even when BIS values and ETAG concentrations were within the target ranges. Our findings do not support routine BIS monitoring as part of standard practice. (ClinicalTrials.gov number, NCT00281489 [ClinicalTrials.gov].).
麻醉期间知晓是一种严重并发症，可能产生长期心理后果。据报道，使用基于处理后的脑电图开发的脑电双频指数（BIS），当BIS值维持在60以下时，可降低麻醉期间知晓的发生率。在本试验中，我们试图确定基于BIS的方案在降低发生该并发症高风险患者的麻醉期间知晓方面是否优于基于呼气末麻醉气体（ETAG）测量的方案。
我们将2000例患者随机分配至BIS引导麻醉组（目标BIS范围为40至60）或ETAG引导麻醉组（目标ETAG范围为0.7至1.3最低肺泡浓度[MAC]）。术后，在三个时间点（拔管后0至24小时、24至72小时和30天）评估患者的麻醉期间知晓情况。
我们分别评估了BIS组的967例患者和ETAG组的974例患者。每组均发生2例明确的麻醉期间知晓（绝对差异为0%；95%置信区间[CI]，-0.56至0.57%）。在1例明确的麻醉期间知晓病例中BIS值大于60，在3例病例中ETAG浓度低于0.7 MAC。对于所有患者，BIS组平均（±标准差）时间平均ETAG浓度为0.81±0.25 MAC，ETAG组为0.82±0.23 MAC（P = 0.10；BIS组与ETAG组差异的95% CI，-0.04至0.01 MAC）。
我们未能重现先前研究中报道的BIS监测可降低麻醉期间知晓发生率的结果，且使用BIS方案与挥发性麻醉气体的给药减少无关。即使BIS值和ETAG浓度在目标范围内，仍发生了麻醉期间知晓。我们的研究结果不支持将常规BIS监测作为标准操作的一部分。（临床试验注册号，NCT00281489 [ClinicalTrials.gov]。）
