Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, Cambridge, UK.
Neurosurgery. 2012 Sep;71(3):652-60; discussion 660-1. doi: 10.1227/NEU.0b013e318260feb1.
Cerebrovascular pressure reactivity is the principal mechanism of cerebral autoregulation. Assessment of cerebral autoregulation can be performed by using the mean flow index (Mx) based on transcranial Doppler ultrasonography. Cerebrovascular pressure reactivity can be monitored by using the pressure reactivity index (PRx), which is based on intracranial pressure monitoring. From a practical point of view, PRx can be monitored continuously, whereas Mx can only be monitored in short periods when transcranial Doppler probes can be applied.
To assess to what degree impairment in pressure reactivity (PRx) is associated with impairment in cerebral autoregulation (Mx).
A database of 345 patients with traumatic brain injury was screened for data availability including simultaneous Mx and PRx monitoring. Absolute differences, temporal changes, and association with outcome of the 2 indices were analyzed.
A total of 486 recording sessions obtained from 201 patients were available for analysis. Overall a moderate correlation between Mx and PRx was found (r = 0.58; P < .001). The area under the receiver operator characteristic curve designed to detect the ability of PRx to predict impaired cerebral autoregulation was 0.700 (95% confidence interval: 0.607-0.880). Discrepancies between Mx and PRx were most pronounced at an intracranial pressure of 30 mm Hg and they were significantly larger for patients who died (P = .026). Both Mx and PRx were significantly lower at day 1 postadmission in patients who survived than in those who died (P < .01).
There is moderate agreement between Mx and PRx. Discrepancies between Mx and PRx are particularly significant in patients with sustained intracranial hypertension. However, for clinical purposes, there is only limited interchangeability between indices.
脑血管压力反应性是脑自动调节的主要机制。可通过经颅多普勒超声的平均血流指数 (Mx) 评估脑自动调节。可通过基于颅内压监测的压力反应指数 (PRx) 监测脑血管压力反应性。从实际角度来看，PRx 可以连续监测，而 Mx 只能在可以应用经颅多普勒探头的短时间内监测。
评估压力反应性 (PRx) 的损伤与脑自动调节 (Mx) 的损伤相关的程度。
筛选了 345 例创伤性脑损伤患者的数据库，以获取包括同时监测 Mx 和 PRx 的数据可用性。分析了 2 个指数的绝对差异、时间变化和与结果的相关性。
从 201 例患者中获得了总共 486 次记录，可用于分析。总体而言，Mx 和 PRx 之间存在中度相关性 (r = 0.58；P <.001)。设计用于检测 PRx 预测脑自动调节受损能力的接收者操作特征曲线下面积为 0.700(95%置信区间：0.607-0.880)。在颅内压为 30 mmHg 时，Mx 和 PRx 之间的差异最为明显，在死亡患者中差异显著更大 (P =.026)。与死亡患者相比，存活患者入院后第 1 天的 Mx 和 PRx 均显著降低 (P <.01)。
Mx 和 PRx 之间存在中度一致性。在持续颅内高压的患者中，Mx 和 PRx 之间的差异尤其显著。然而，对于临床目的，指数之间只有有限的可互换性。
