Department of Anesthesiology and Critical Care Medicine, School of Medicine, Johns Hopkins University, Baltimore, MD, USA.
Department of Anesthesiology and Critical Care Medicine, School of Medicine, Johns Hopkins University, Baltimore, MD, USA; Saitama Medical Center, Jichi Medical University, Saitama 330-8503, Japan.
J Clin Anesth. 2021 Nov;74:110395. doi: 10.1016/j.jclinane.2021.110395. Epub 2021 Jun 17.
Low bispectral index (BIS) values have been associated with adverse postoperative outcomes. However, trials of optimizing BIS by titrating anesthetic administration have reported conflicting results. One potential explanation is that cerebral perfusion may also affect BIS, but the extent of this relationship is not clear. Therefore, we examined whether BIS would be associated with cerebral perfusion during cardiopulmonary bypass, when anesthetic concentration was constant.
Observational cohort study.
Cardiac operating room.
Seventy-nine patients with cardiopulmonary bypass surgery were included.
Continuous BIS, mean arterial blood pressure (MAP), cerebral blood flow velocity (CBFV), and regional cerebral oxygen saturation (rSO) were monitored, with analysis during a period of constant anesthetic. Mean flow index (Mx) was calculated as Pearson correlation between MAP and CBFV. The lower limit of autoregulation (LLA) was identified as the MAP value at which Mx increased >0.4 with decreasing blood pressure. Postoperative delirium was assessed using the 3D-Confusion Assessment Method.
Mean BIS was lower during periods of MAP < LLA compared with BIS when MAP>LLA (mean 49.35 ± 10.40 vs. 50.72 ± 10.04, p = 0.002, mean difference = 1.38 [standard error: 0.42]). There was a dose response effect, with the BIS proportionately decreasing as MAP decreased below LLA (β = 0.15, 95% CI for the average slope across all patients 0.07 to 0.23, p < 0.001). In contrast, BIS was relatively unchanged when MAP was above LLA (β = 0.03, 95% CI for the average slope across all patients -0.02 to 0.09, p = 0.22). Additionally, increasing CBFV and rSO were associated with increasing BIS. Patients with postoperative delirium had lower mean BIS and higher percentage of time duration with BIS <45 compared to patients without delirium.
There was an association of BIS and metrics of cerebral perfusion during a period of constant anesthetic administration, but the absolute magnitude of change in BIS as MAP decreased below the LLA was small.
低双谱指数（BIS）值与术后不良结局相关。然而，通过滴定麻醉药物来优化 BIS 的试验报告结果相互矛盾。一个潜在的解释是脑灌注也可能影响 BIS，但这种关系的程度尚不清楚。因此，我们研究了当麻醉浓度恒定时，体外循环期间 BIS 是否与脑灌注相关。
观察性队列研究。
心脏手术室。
纳入 79 例体外循环手术患者。
连续监测 BIS、平均动脉血压（MAP）、脑血流速度（CBFV）和局部脑氧饱和度（rSO），并在麻醉恒定期间进行分析。平均流量指数（Mx）作为 MAP 与 CBFV 的 Pearson 相关系数计算得出。下自动调节下限（LLA）定义为 MAP 值，在此值下，随着血压降低，Mx 增加>0.4。术后谵妄采用三维意识模糊评估法进行评估。
MAP<LLA 时的平均 BIS 低于 MAP>LLA 时的 BIS（平均 49.35±10.40 与 50.72±10.04，p=0.002，平均差值 1.38[标准误差：0.42]）。存在剂量反应效应，随着 MAP 低于 LLA，BIS 成比例降低（β=0.15，95%CI 为所有患者的平均斜率 0.07 至 0.23，p<0.001）。相反，当 MAP 高于 LLA 时，BIS 相对不变（β=0.03，95%CI 为所有患者的平均斜率 -0.02 至 0.09，p=0.22）。此外，CBFV 和 rSO 的增加与 BIS 的增加相关。与无谵妄的患者相比，术后谵妄患者的平均 BIS 较低，BIS<45 的时间百分比较高。
在麻醉药物恒定给药期间，BIS 与脑灌注指标之间存在关联，但 MAP 低于 LLA 时 BIS 变化的绝对值较小。
