Background

Postoperative delirium is a serious complication of surgery associated with prolonged hospitalisation, long-term cognitive decline, and mortality. This study aimed to determine whether targeting bispectral index (BIS) readings of 50 (light anaesthesia) was associated with a lower incidence of POD than targeting BIS readings of 35 (deep anaesthesia).

Methods

This multicentre randomised clinical trial of 655 at-risk patients undergoing major surgery from eight centres in three countries assessed delirium for 5 days postoperatively using the 3 min confusion assessment method (3D-CAM) or CAM-ICU, and cognitive screening using the Mini-Mental State Examination at baseline and discharge and the Abbreviated Mental Test score (AMTS) at 30 days and 1 yr. Patients were assigned to light or deep anaesthesia. The primary outcome was the presence of postoperative delirium on any of the first 5 postoperative days. Secondary outcomes included mortality at 1 yr, cognitive decline at discharge, cognitive impairment at 30 days and 1 yr, unplanned ICU admission, length of stay, and time in electroencephalographic burst suppression.

Results

The incidence of postoperative delirium in the BIS 50 group was 19% and in the BIS 35 group was 28% (odds ratio 0.58 [95% confidence interval: 0.38–0.88]; P=0.010). At 1 yr, those in the BIS 50 group demonstrated significantly better cognitive function than those in the BIS 35 group (9% with AMTS ≤6 vs 20%; P<0.001).

Conclusions

Among patients undergoing major surgery, targeting light anaesthesia reduced the risk of postoperative delirium and cognitive impairment at 1 yr.

Clinical trial registration

ACTRN12612000632897.

中文翻译：

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大手术后麻醉深度和谵妄：一项随机临床试验

 背景

术后谵妄是一种严重的手术并发症，与长期住院、长期认知能力下降和死亡有关。本研究旨在确定双频指数 (BIS) 读数为 50（浅麻醉）是否比 BIS 读数为 35（深麻醉）与较低的 POD 发生率相关。

 方法

这项多中心随机临床试验对来自三个国家的 8 个中心的 655 名接受大手术的高危患者进行了使用 3 分钟意识模糊评估法 (3D-CAM) 或 CAM-ICU 评估术后 5 天的谵妄状态，并使用 Mini-ICU 进行认知筛查。基线和出院时的精神状态检查以及 30 天和 1 年的简略精神测试评分 (AMTS)。患者被分配接受浅麻醉或深麻醉。主要结果是术后前 5 天中任意一天出现术后谵妄。次要结局包括 1 年死亡率、出院时认知能力下降、30 天和 1 年认知障碍、计划外 ICU 入住、住院时间和脑电图突发抑制时间。

 结果

BIS 50 组术后谵妄的发生率为 19%，BIS 35 组为 28%（比值比 0.58 [95% 置信区间：0.38–0.88]； P = 0.010）。 1 年时，BIS 50 组的认知功能明显优于 BIS 35 组（AMTS ≤ 6 的 9% vs 20%； P <0.001）。

 结论

在接受大手术的患者中，轻度麻醉可降低术后一年内发生谵妄和认知障碍的风险。

临床试验注册

 ACTRN12612000632897。