Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO 63110, USA.
N Engl J Med. 2011 Aug 18;365(7):591-600. doi: 10.1056/NEJMoa1100403.
Unintended intraoperative awareness, which occurs when general anesthesia is not achieved or maintained, affects up to 1% of patients at high risk for this complication. We tested the hypothesis that a protocol incorporating the electroencephalogram-derived bispectral index (BIS) is superior to a protocol incorporating standard monitoring of end-tidal anesthetic-agent concentration (ETAC) for the prevention of awareness.
We conducted a prospective, randomized, evaluator-blinded trial at three medical centers. We randomly assigned 6041 patients at high risk for awareness to BIS-guided anesthesia (with an audible alert if the BIS value was <40 or >60, on a scale of 0 to 100, with 0 indicating the suppression of detectable brain electrical activity and 100 indicating the awake state) or ETAC-guided anesthesia (with an audible alert if the ETAC was <0.7 or >1.3 minimum alveolar concentration). In addition to audible alerts, the protocols included structured education and checklists. Superiority of the BIS protocol was assessed with the use of a one-sided Fisher's exact test.
A total of 7 of 2861 patients (0.24%) in the BIS group, as compared with 2 of 2852 (0.07%) in the ETAC group, who were interviewed postoperatively had definite intraoperative awareness (a difference of 0.17 percentage points; 95% confidence interval [CI], -0.03 to 0.38; P=0.98). Thus, the superiority of the BIS protocol was not demonstrated. A total of 19 cases of definite or possible intraoperative awareness (0.66%) occurred in the BIS group, as compared with 8 (0.28%) in the ETAC group (a difference of 0.38 percentage points; 95% CI, 0.03 to 0.74; P=0.99), with the superiority of the BIS protocol again not demonstrated. There was no difference between the groups with respect to the amount of anesthesia administered or the rate of major postoperative adverse outcomes.
The superiority of the BIS protocol was not established; contrary to expectations, fewer patients in the ETAC group than in the BIS group experienced awareness. (Funded by the Foundation for Anesthesia Education and Research and others; BAG-RECALL ClinicalTrials.gov number, NCT00682825.).
术中知晓是指全麻未能达到或维持的情况下发生的意识，在高危患者中发生率高达 1%。我们假设一种包含脑电双频指数（BIS）的方案优于一种包含呼气末麻醉药浓度（ETAC）标准监测的方案，以预防术中知晓。
我们在三个医疗中心进行了一项前瞻性、随机、评估者盲法试验。我们将 6041 名高危意识的患者随机分配至 BIS 指导麻醉组（BIS 值＜40 或＞60 时会发出声音警报，BIS 值范围为 0 至 100，0 表示可检测脑电活动抑制，100 表示清醒状态）或 ETAC 指导麻醉组（ETAC＜0.7 或＞1.3 时会发出声音警报，最低肺泡浓度）。除声音警报外，方案还包括结构化教育和检查表。采用单侧 Fisher 精确检验评估 BIS 方案的优越性。
术后接受访谈的患者中，BIS 组有 7 例（0.24%），ETAC 组有 2 例（0.07%），明确发生术中知晓（差异 0.17 个百分点；95%置信区间[CI]，-0.03 至 0.38；P=0.98）。因此，BIS 方案的优越性未得到证实。BIS 组共有 19 例（0.66%）明确或可能发生术中知晓，而 ETAC 组有 8 例（0.28%）（差异 0.38 个百分点；95%CI，0.03 至 0.74；P=0.99），BIS 方案的优越性也未得到证实。两组麻醉用药量或主要术后不良结局发生率无差异。
BIS 方案的优越性未得到证实；与预期相反，ETAC 组经历意识的患者比 BIS 组少。（由麻醉教育与研究基金会等资助；BAG-RECALL 临床试验.gov 编号，NCT00682825。）
