Moderate-to-severe traumatic brain injury (TBI) has a global mortality rate of about 30%, resulting in acquired life-long disabilities in many survivors. To potentially improve outcomes in this TBI population, the management of secondary injuries, particularly the failure of cerebrovascular reactivity (assessed via the pressure reactivity index; PRx, a correlation between intracranial pressure (ICP) and mean arterial blood pressure (MAP)), has gained interest in the field. However, derivation of PRx requires high-resolution data and expensive technological solutions, as calculations use a short time-window, which has resulted in it being used in only a handful of centers worldwide. As a solution to this, low resolution (longer time-windows) PRx has been suggested, known as Long-PRx or LPRx. Though LPRx has been proposed little is known about the best methodology to derive this measure, with different thresholds and time-windows proposed. Furthermore, the impact of ICP monitoring on cerebrovascular reactivity measures is poorly understood. Hence, this observational study establishes critical thresholds of LPRx associated with long-term functional outcome, comparing different time-windows for calculating LPRx as well as evaluating LPRx determined through external ventricular drains (EVD) vs intraparenchymal pressure device (IPD) ICP monitoring. The study included a total of n = 435 TBI patients from the Karolinska University Hospital. Patients were dichotomized into alive vs. dead and favorable vs. unfavorable outcomes based on 1-year Glasgow Outcome Scale (GOS). Pearson’s chi-square values were computed for incrementally increasing LPRx or ICP thresholds against outcome. The thresholds that generated the greatest chi-squared value for each LPRx or ICP parameter had the highest outcome discriminatory capacity. This methodology was also completed for the segmentation of the population based on EVD, IPD, and time of data recorded in hospital stay. LPRx calculated with 10–120-min windows behaved similarly, with maximal chi-square values ranging at around a LPRx of 0.25–0.35, for both survival and favorable outcome. When investigating the temporal relations of LPRx derived thresholds, the first 4 days appeared to be the most associated with outcomes. The segmentation of the data based on intracranial monitoring found limited differences between EVD and IPD, with similar LPRx values around 0.3. Our work suggests that the underlying prognostic factors causing impairment in cerebrovascular reactivity can, to some degree, be detected using lower resolution PRx metrics (similar found thresholding values) with LPRx found clinically using as low as 10 min-by-minute samples of MAP and ICP. Furthermore, EVD derived LPRx with intermittent cerebrospinal fluid draining, seems to present similar outcome capacity as IPD. This low-resolution low sample LPRx method appears to be an adequate substitute for the clinical prognostic value of PRx and may be implemented independent of ICP monitoring method when PRx is not feasible, though further research is warranted.

中文翻译：

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长压反应指数临界阈值及颅内压监测方法对颅脑损伤的影响


中度至重度创伤性脑损伤 (TBI) 的全球死亡率约为 30%，导致许多幸存者出现后天性终身残疾。为了潜在地改善 TBI 人群的预后，继发性损伤的管理，特别是脑血管反应性失败（通过压力反应性指数评估；PRx，颅内压（ICP）和平均动脉压（MAP）之间的相关性），已经对该领域产生了兴趣。然而，PRx 的推导需要高分辨率数据和昂贵的技术解决方案，因为计算使用的时间窗口很短，这导致它仅在全球少数几个中心使用。作为解决方案，有人建议使用低分辨率（较长时间窗口）PRx，称为长 PRx 或 LPRx。尽管 LPRx 已经被提出，但对于导出该度量的最佳方法知之甚少，并提出了不同的阈值和时间窗口。此外，ICP 监测对脑血管反应性测量的影响知之甚少。因此，这项观察性研究建立了与长期功能结果相关的 LPRx 关键阈值，比较了计算 LPRx 的不同时间窗口，并评估了通过心室外引流 (EVD) 与实质内压力装置 (IPD) ICP 监测确定的 LPRx。该研究总共纳入了来自卡罗林斯卡大学医院的 435 名 TBI 患者。根据一年期格拉斯哥结果量表 (GOS)，将患者分为存活与死亡、有利与不利结果。皮尔逊卡方值的计算是针对结果逐渐增加的 LPRx 或 ICP 阈值。 为每个 LPRx 或 ICP 参数生成最大卡方值的阈值具有最高的结果辨别能力。该方法还根据 EVD、IPD 和住院期间记录的数据时间进行人群细分。使用 10-120 分钟窗口计算的 LPRx 表现相似，对于生存和良好的结果，最大卡方值范围在 LPRx 0.25-0.35 左右。在调查 LPRx 衍生阈值的时间关系时，前 4 天似乎与结果最相关。基于颅内监测的数据分割发现 EVD 和 IPD 之间的差异有限，相似的 LPRx 值约为 0.3。我们的工作表明，在某种程度上，可以使用较低分辨率的 PRx 指标（相似的发现阈值）来检测导致脑血管反应性受损的潜在预后因素，而临床上发现的 LPRx 使用低至 10 分钟的 MAP 样本和ICP。此外，EVD 衍生的 LPRx 具有间歇性脑脊液引流，似乎具有与 IPD 相似的结果能力。这种低分辨率低样本 LPRx 方法似乎可以充分替代 PRx 的临床预后价值，并且当 PRx 不可行时，可以独立于 ICP 监测方法实施，但需要进一步研究。