Current neurointensive care guidelines recommend intracranial pressure (ICP) and cerebral perfusion pressure (CPP) centered management for moderate-severe traumatic brain injury (TBI) because of their demonstrated associations with patient outcome. Cerebrovascular reactivity metrics, such as the pressure reactivity index (PRx), pulse amplitude index (PAx), and RAC index, have also demonstrated significant prognostic capabilities with regard to outcome. However, critical thresholds for cerebrovascular reactivity indices have only been identified in two studies conducted at the same center. In this study, we aim to determine the critical thresholds of these metrics by leveraging a unique multi-center database. The study included a total of 354 patients from the CAnadian High-Resolution TBI (CAHR-TBI) Research Collaborative. Based on 6-month Glasgow Outcome Scores, patients were dichotomized into alive versus dead and favorable versus unfavorable. Chi-square values were then computed for incrementally increasing values of each physiological parameter of interest against outcome. The values that generated the greatest chi-squares for each parameter were considered to be the thresholds with the greatest outcome discriminatory capacity. To confirm that the identified thresholds provide prognostic utility, univariate and multivariable logistical regression analyses were performed adjusting for the International Mission for Prognosis and Analysis of Clinical Trials (IMPACT) variables. Through the chi-square analysis, a lower limit CPP threshold of 60 mm Hg and ICP thresholds of 18 mm Hg and 22 mm Hg were identified for both survival and favorable outcome predictions. For the cerebrovascular reactivity metrics, different thresholds were identified for the two outcome dichotomizations. For survival prediction, thresholds of 0.35, 0.25, and 0 were identified for PRx, PAx, and RAC, respectively. For favorable outcome prediction, thresholds of 0.325, 0.20, and 0.05 were found. Univariate logistical regression analysis demonstrated that the time spent above/below thresholds were associated with outcome. Further, multivariable logistical regression analysis found that percent time above/below the identified thresholds added additional variance to the IMPACT core model for predicting both survival and favorable outcome. In this study, we were able to validate the results of the previous two works as well as to reaffirm the ICP and CPP guidelines from the Brain Trauma Foundation (BTF) and the Seattle International Severe Traumatic Brain Injury Consensus Conference (SIBICC).

中文翻译：

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颅内压衍生的脑血管反应指数及其临界阈值：加拿大高分辨率创伤性脑损伤验证研究。

目前的神经重症监护指南建议对中重度创伤性脑损伤（TBI）以颅内压（ICP）和脑灌注压（CPP）为中心进行治疗，因为它们已被证明与患者的预后相关。脑血管反应性指标，例如压力反应性指数 (PRx)、脉搏振幅指数 (PAx) 和 RAC 指数，也显示出与结果相关的显着预后能力。然而，脑血管反应指数的关键阈值仅在同一中心进行的两项研究中确定。在本研究中，我们的目标是通过利用独特的多中心数据库来确定这些指标的关键阈值。该研究共纳入了加拿大高分辨率 TBI (CAHR-TBI) 研究合作组织的 354 名患者。根据 6 个月的格拉斯哥结果评分，患者被分为存活与死亡、有利与不利。然后计算卡方值，以针对结果逐步增加每个感兴趣的生理参数的值。为每个参数生成最大卡方的值被认为是具有最大结果辨别能力的阈值。为了确认确定的阈值提供预后效用，进行了单变量和多变量逻辑回归分析，调整了国际临床试验预后和分析任务 (IMPACT) 变量。通过卡方分析，确定了生存和有利结果预测的下限 CPP 阈值 60 mm Hg 以及 ICP 阈值 18 mm Hg 和 22 mm Hg。对于脑血管反应性指标，为两种结果二分法确定了不同的阈值。对于生存预测，PRx、PAx 和 RAC 的阈值分别为 0.35、0.25 和 0。对于有利的结果预测，找到了 0.325、0.20 和 0.05 的阈值。单变量逻辑回归分析表明，高于/低于阈值的时间与结果相关。此外，多变量逻辑回归分析发现，高于/低于确定阈值的时间百分比为预测生存率和有利结果的 IMPACT 核心模型增加了额外的方差。在这项研究中，我们能够验证前两项工作的结果，并重申脑外伤基金会 (BTF) 和西雅图国际严重外伤性脑损伤共识会议 (SIBICC) 的 ICP 和 CPP 指南。