2 Division of Anaesthesia, Addenbrooke's Hospital, University of Cambridge , Cambridge, United Kingdom .
3 Section of Surgery, Rady Faculty of Health Sciences, University of Manitoba , Winnipeg, Manitoba, Canada .
J Neurotrauma. 2018 Dec 1;35(23):2812-2819. doi: 10.1089/neu.2017.5604. Epub 2018 Aug 10.
The aim of this work was to explore the relationship between intracranial pressure (ICP)-derived indices of cerebrovascular reactivity and the lower limit of autoregulation (LLA) during arterial hypotension. We retrospectively reviewed recorded physiological data from piglets that underwent controlled hypotension. Hypotension was induced by inflation of a balloon catheter in the inferior vena cava. ICP, cortical laser Doppler flowmetry (LDF), and arterial blood pressure (ABP) monitoring was conducted. ICP-derived indices were calculated: pressure reactivity index (PRx; correlation between ICP and mean arterial pressure [MAP]); pulse amplitude index (PAx; correlation between pulse amplitude of ICP [AMP] and MAP); and RAC (correlation between AMP and cerebral perfusion pressure [CPP]). LLA was estimated by piece-wise linear regression of CPP versus LDF. We produced error bar plots for PRx, PAx, and RAC against 5-mm Hg bins of CPP, displaying the relationship with the LLA. We compared CPP values at clinically relevant thresholds of PRx, PAx, and RAC to CPP measured at the LLA. Receiver operating curve (ROC) analysis was performed for each index across the LLA using 5-mm Hg bins for CPP. Mean LLA was 36.2 ± 10.5 mm Hg. Error bar plots demonstrated that PRx, PAx, and RAC increased, with CPP decreasing below the LLA. CPP at clinically relevant thresholds for PRx, PAx, and RAC displayed weak associations with the LLA, indicating that thresholds defined in TBI may not apply to a model of arterial hypotension. ROC analysis indicated that PRx, PAx, and RAC predicted the LLA, with AUCs of: 0.806 (95% confidence interval [CI], 0.750-0.863; p < 0.0001), 0.726 (95% CI, 0.664-0.789; p < 0.0001), and 0.710 (95% CI, 0.646-0.775; p < 0.0001), respectively. Three ICP-derived continuous indices of cerebrovascular reactivity, PRx, PAx, and RAC, were validated against the LLA within this experimental model of arterial hypotension, with PRx being superior.
本研究旨在探讨在动脉低血压期间，颅内压（ICP）衍生的脑血管反应性指标与自动调节下限（LLA）之间的关系。我们回顾性分析了接受控制性低血压的小猪记录的生理数据。低血压通过下腔静脉球囊充气诱导。进行 ICP、皮质激光多普勒流量测定（LDF）和动脉血压（ABP）监测。计算了 ICP 衍生指数：压力反应性指数（PRx；ICP 与平均动脉压 [MAP] 之间的相关性）；脉搏振幅指数（PAx；ICP 脉搏振幅 [AMP] 与 MAP 之间的相关性）；和 RAC（AMP 与脑灌注压 [CPP] 之间的相关性）。通过 CPP 与 LDF 的分段线性回归估计 LLA。我们以 CPP 为 5mmHg 间隔的 PRx、PAx 和 RAC 生成误差棒图，显示与 LLA 的关系。我们比较了 PRx、PAx 和 RAC 的临床相关阈值时的 CPP 值与 LLA 时测量的 CPP 值。对每个指数进行了 ROC 分析，使用 CPP 的 5mmHg 间隔进行了分析。平均 LLA 为 36.2±10.5mmHg。误差棒图表明，PRx、PAx 和 RAC 随着 CPP 低于 LLA 而增加。PRx、PAx 和 RAC 的临床相关阈值时的 CPP 值与 LLA 显示出较弱的关联，表明 TBI 中定义的阈值可能不适用于动脉低血压模型。ROC 分析表明，PRx、PAx 和 RAC 预测了 LLA，其 AUC 分别为：0.806（95%置信区间 [CI]，0.750-0.863；p<0.0001）、0.726（95% CI，0.664-0.789；p<0.0001）和 0.710（95% CI，0.646-0.775；p<0.0001）。三个 ICP 衍生的脑血管反应性连续指数 PRx、PAx 和 RAC 在动脉低血压的实验模型中与 LLA 进行了验证，PRx 表现更优。
