Coma Science Group, GIGA-Consciousness, University of Liège, Liège, Belgium; Centre du Cerveau, University of Liège, Liège, Belgium.
Coma Science Group, GIGA-Consciousness, University of Liège, Liège, Belgium; Centre du Cerveau, University of Liège, Liège, Belgium; Department of Neurology, University of Liège, Liège, Belgium.
Br J Anaesth. 2023 Oct;131(4):715-725. doi: 10.1016/j.bja.2023.05.030. Epub 2023 Aug 16.
Cortical excitability is higher in unconsciousness than in wakefulness, but it is unclear how this relates to anaesthesia. We investigated cortical excitability in response to dexmedetomidine, the effects of which are not fully known.
We recorded transcranial magnetic stimulation (TMS) and EEG in frontal and parietal cortex of 20 healthy subjects undergoing dexmedetomidine sedation in four conditions (baseline, light sedation, deep sedation, recovery). We used the first component (0-30 ms) of the TMS-evoked potential (TEP) to measure cortical excitability (amplitude), slope, and positive and negative peak latencies (collectively, TEP indices). We used generalised linear mixed models to test the effect of condition, brain region, and responsiveness on TEP indices.
Compared with baseline, amplitude in the frontal cortex increased by 6.52 μV (P<0.001) in light sedation, 4.55 μV (P=0.003) in deep sedation, and 5.03 μV (P<0.001) in recovery. Amplitude did not change in the parietal cortex. Compared with baseline, slope increased in all conditions (P<0.02) in the frontal but not parietal cortex. The frontal cortex showed 5.73 μV higher amplitude (P<0.001), 0.63 μV ms higher slope (P<0.001), and 2.2 ms shorter negative peak latency (P=0.001) than parietal areas. Interactions between dexmedetomidine and region had effects over amplitude (P=0.004) and slope (P=0.009), with both being higher in light sedation, deep sedation, and recovery compared with baseline.
Transcranial magnetic stimulation-evoked potential amplitude changes non-linearly as a function of depth of sedation by dexmedetomidine, with a region-specific paradoxical increase. Future research should investigate other anaesthetics to elucidate the link between cortical excitability and depth of sedation.
无意识状态下皮质兴奋性高于觉醒状态，但目前尚不清楚这与麻醉有何关系。我们研究了接受右美托咪定镇静的 20 名健康受试者的皮质兴奋性，但其作用尚不完全清楚。
我们在 20 名接受右美托咪定镇静的健康受试者的额区和顶区记录了经颅磁刺激（TMS）和脑电图，镇静条件包括基础状态、轻度镇静、深度镇静和恢复。我们使用 TMS 诱发电位（TEP）的第一个成分（0-30ms）来测量皮质兴奋性（幅度）、斜率以及正、负峰潜伏期（统称为 TEP 指数）。我们使用广义线性混合模型来检验条件、脑区和反应性对 TEP 指数的影响。
与基础状态相比，轻度镇静时额区的振幅增加了 6.52μV（P<0.001），深度镇静时增加了 4.55μV（P=0.003），恢复时增加了 5.03μV（P<0.001）。顶区的振幅没有变化。与基础状态相比，所有条件下（P<0.02）额区斜率均增加，但顶区无变化。与顶区相比，额区的振幅高 5.73μV（P<0.001），斜率高 0.63μV ms（P<0.001），负峰潜伏期短 2.2ms（P=0.001）。右美托咪定与脑区的相互作用对振幅（P=0.004）和斜率（P=0.009）有影响，与基础状态相比，在轻度镇静、深度镇静和恢复时两者均增加。
右美托咪定镇静深度的 TMS 诱发电位振幅呈非线性变化，额区出现区域特异性的反常增加。未来的研究应探讨其他麻醉剂，以阐明皮质兴奋性与镇静深度之间的关系。
