Froese Logan, Gomez Alwyn, Sainbhi Amanjyot Singh, Batson Carleen, Slack Trevor, Stein Kevin Y, Mathieu Francois, Zeiler Frederick A
Biomedical Engineering, Price Faculty of Engineering, University of Manitoba, Winnipeg, Canada.
Section of Neurosurgery, Department of Surgery, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, MB, Canada.
Intensive Care Med Exp. 2022 Aug 13;10(1):33. doi: 10.1186/s40635-022-00460-9.
Impaired cerebral autoregulation has been linked with worse outcomes, with literature suggesting that current therapy guidelines fail to significantly impact cerebrovascular reactivity. The cerebral oximetry index (COx_a) is a surrogate measure of cerebrovascular reactivity which can in theory be obtained non-invasively using regional brain tissue oxygen saturation and arterial blood pressure. The goal of this study was to assess the relationship between objectively measured depth of sedation through BIS and autoregulatory capacity measured through COx_a.
In a prospectively maintained observational study, we collected continuous regional brain tissue oxygen saturation, intracranial pressure, arterial blood pressure and BIS in traumatic brain injury patients. COx_a was obtained using the Pearson's correlation between regional brain tissue oxygen saturation and arterial blood pressure and ranges from - 1 to 1 with higher values indicating impairment of cerebrovascular reactivity. Using BIS values and COx_a, a curve-fitting method was applied to determine the minimum value for the COx_a. The associated BIS value with the minimum COx_a is called BISopt. This BISopt was both visually and algorithmically determined, which were compared and assessed over the whole dataset.
Of the 42 patients, we observed that most had a parabolic relationship between BIS and COx_a. This suggests a potential "optimal" depth of sedation where COx_a is the most intact. Furthermore, when comparing the BISopt algorithm with visual inspection of BISopt, we obtained similar results. Finally, BISopt % yield (determined algorithmically) appeared to be independent from any individual sedative or vasopressor agent, and there was agreement between BISopt found with COx_a and the pressure reactivity index (another surrogate for cerebrovascular reactivity).
This study suggests that COx_a is capable of detecting disruption in cerebrovascular reactivity which occurs with over-/under-sedation, utilizing a non-invasive measure of determination and assessment. This technique may carry implications for tailoring sedation in patients, focusing on individualized neuroprotection.
脑自动调节功能受损与更差的预后相关，文献表明当前的治疗指南未能显著影响脑血管反应性。脑氧饱和度指数（COx_a）是脑血管反应性的替代指标，理论上可通过局部脑组织氧饱和度和动脉血压无创获取。本研究的目的是评估通过脑电双频指数（BIS）客观测量的镇静深度与通过COx_a测量的自动调节能力之间的关系。
在一项前瞻性的观察性研究中，我们收集了创伤性脑损伤患者的连续局部脑组织氧饱和度、颅内压、动脉血压和BIS。COx_a通过局部脑组织氧饱和度与动脉血压之间的皮尔逊相关性获得，范围为-1至1，值越高表明脑血管反应性受损。使用BIS值和COx_a，应用曲线拟合方法确定COx_a的最小值。与最小COx_a相关的BIS值称为BISopt。通过视觉和算法确定该BISopt，并在整个数据集中进行比较和评估。
在42例患者中，我们观察到大多数患者的BIS与COx_a之间呈抛物线关系。这表明存在一个潜在的“最佳”镇静深度，此时COx_a最为完整。此外，将BISopt算法与BISopt的视觉检查进行比较时，我们得到了相似的结果。最后，BISopt%产量（通过算法确定）似乎与任何个体镇静剂或血管升压药无关，并且通过COx_a发现的BISopt与压力反应指数（脑血管反应性的另一个替代指标）之间存在一致性。
本研究表明，COx_a能够利用无创测定和评估方法检测过度/不足镇静时发生的脑血管反应性破坏。该技术可能对患者的镇静调整具有启示意义，重点是个体化的神经保护。
