Refractory intracranial hypertension (RIH) is a dramatic increase in intracranial pressure (ICP) that cannot be controlled by treatment. Recent reports suggest that the autonomic nervous system (ANS) activity may be altered during changes in ICP. Our study aimed to assess ANS activity during RIH and the causal relationship between rising in ICP and autonomic activity. We reviewed retrospectively 24 multicenter (Cambridge, Tromso, Berlin) patients in whom RIH developed as a pre-terminal event after acute brain injury (ABI). They were monitored with ICP, arterial blood pressure (ABP), and electrocardiography (ECG) using ICM+ software. Parameters reflecting autonomic activity were computed in time and frequency domain through the measurement of heart rate variability (HRV) and baroreflex sensitivity (BRS). Our results demonstrated that a rise in ICP was associated to a significant rise in HRV and BRS with a higher significance level in the high-frequency HRV (p < 0.001). This increase was followed by a significant decrease in HRV and BRS above the upper-breakpoint of ICP where ICP pulse-amplitude starts to decrease whereas the mean ICP continues to rise. Temporality measured with a Granger test suggests a causal relationship from ICP to ANS. The above results suggest that a rise in ICP interacts with ANS activity, mainly interfacing with the parasympathetic-system. The ANS seems to react to the rise in ICP with a response possibly focused on maintaining the cerebrovascular homeostasis. This happens until the critical threshold of ICP is reached above which the ANS variables collapse, probably because of low perfusion of the brain and the central autonomic network.

中文翻译：

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颅内压难治性上升期间的自主神经系统活动

难治性颅内高压（RIH）是指无法通过治疗控制的颅内压（ICP）急剧升高。最近的报告表明，自主神经系统 (ANS) 活动可能会在 ICP 变化期间发生改变。我们的研究旨在评估 RIH 期间的 ANS 活动以及 ICP 上升与自主活动之间的因果关系。我们回顾性回顾了 24 名多中心（剑桥、特罗姆瑟、柏林）患者，这些患者在急性脑损伤 (ABI) 后发生了 RIH 作为临终事件。使用 ICM+ 软件对他们进行 ICP、动脉血压 (ABP) 和心电图 (ECG) 监测。通过测量心率变异性（HRV）和压力反射敏感性（BRS），在时域和频域中计算反映自主活动的参数。我们的结果表明，ICP 的升高与 HRV 和 BRS 的显着升高相关，其中高频 HRV 的显着性水平更高 ( p  < 0.001)。这种增加之后，HRV 和 BRS 在 ICP 上断点以上显着下降，此时 ICP 脉冲幅度开始下降，而平均 ICP 继续上升。用 Granger 检验测量的时间性表明 ICP 与 ANS 之间存在因果关系。上述结果表明 ICP 的升高与 ANS 活动相互作用，主要与副交感神经系统相互作用。ANS 似乎对 ICP 的升高做出反应，其反应可能集中于维持脑血管稳态。这种情况会发生，直到达到 ICP 的临界阈值，超过该阈值 ANS 变量就会崩溃，这可能是因为大脑和中枢自主网络的灌注不足。