Critical Thresholds for Transcranial Doppler Indices of Cerebral Autoregulation in Traumatic Brain Injury
作者：Enrico Sorrentino ? Karol P. Budohoski ?Magdalena Kasprowicz ? Peter Smielewski ?Basil Matta ? John D. Pickard ? Marek Czosnyka
摘自：Neurocrit Care (2011) 14:188–193
經(jīng)顱多普勒衍生的腦自動調(diào)節(jié)指數(shù)與TBI患者預后有重要關聯(lián)。 我們回顧性分析了患者數(shù)據(jù)材料，以確定對這些指數(shù)的對預后結果進行判別的閾值。
方法：248名顱腦損傷后的鎮(zhèn)靜和通氣患者數(shù)據(jù)被選入該研究。用于評估自動調(diào)節(jié)的指數(shù)為Mx（血流速度與腦灌注壓相關系數(shù)）或Mxa（血流速度與動脈血壓相關系數(shù)）。 根據(jù)存活 - 死亡（有利 - 不利結果）和Mx和Mxa的變化閾值，創(chuàng)建2×2個表格。 我們計算了皮爾遜的卡方。在生存 - 死亡（有利 - 不利結果）之間返回最高卡方值的Mx或Mxa值被認為具有最佳判別性的閾值。
結論：Mx和Mxa證明較差的自動調(diào)節(jié)與較差的結果和較高的死亡率相關（Mx為P = 0.0033，Mxa為P = 0.047）。 這兩個指數(shù)對預測有利結果比死亡率更有效。 Mx的卡方顯示雙峰，閾值為0.05和0.3。 Mxa只有一個峰值為0.3。 Mx的峰值卡方（11.3）大于Mxa（8.7），表明Mx是比Mxa更好的判別指數(shù)。
討論：我們認為Mx大于0.3表示明確受損的自動調(diào)節(jié)并且低于0.05良好自動調(diào)節(jié)。 對于0.05和0.3之間的值，自動調(diào)節(jié)的狀態(tài)是不確定的。由經(jīng)顱多普勒測量的腦血流信號計算的自動調(diào)節(jié)指數(shù)Mx和Mxa似乎都具有預測價值，尤其是針對有利結果的預測。對較大樣本人群的研究將闡明這些閾值是否適用于所有患者或僅適用于其中一部分患者。
Abstract
Background Transcranial Doppler-derived indices of cerebral autoregulation are related to outcome after TBI.
We analyzed our retrospective material to identify thresholds discriminative of outcome for these indices.Methods 248 sedated and ventilated patients after head injury were eligible for the study. The indices of autoregulation derived from transcranial Doppler were calculated as correlation coefficients of blood flow velocity with cerebral perfusion pressure (index Mx) or arterial blood pressure (index Mxa). 2 9 2 tables were created grouping patients according to survival–death or favorable–unfavorable outcomes and varying thresholds for Mx and Mxa.Pearson’s chi-square was calculated. Thresholds returning the highest chi-square value were assumed to have the best discriminative value between survival–death and favorable–unfavorable outcomes.
Results Mx and Mxa demonstrated that worse autoregulation is associated with poorer outcome and greater mortality (P = 0.0033 for Mx and P = 0.047 for Mxa).
Both indices were more effective for prediction of favorable outcome than mortality. Chi-square for Mx showed a double peak with thresholds at 0.05 and 0.3. Mxa had only one peak at 0.3. Peak chi-square for Mx (11.3) was greater than for Mxa (8.7), indicating that Mx was a better discriminant of outcome than Mxa.
Conclusions We propose that Mx greater than 0.3 indicates definitely disturbed autoregulation and lower than 0.05 good autoregulation. For values between 0.05 and 0.3 the state of autoregulation is uncertain.
Introduction
The importance of the measurement of cerebral autoregulation has been highlighted in many studies over the past decades [1–3]. Continuous monitoring seems to be important as autoregulation status may change dynamically— e.g., during plateau waves of intracranial pressure (ICP) [4], incidental arterial hypotension [5], vasospasm,hyperemia [6], or refractory intracranial hypertension [7]. The mean flow velocity index (Mx) is a correlaion coefficient between slow fluctuations (whose average period ranges from 20 s to 3 min) of flow velocity (FV) in the middle cerebral artery (MCA), measured through TCD,and global cerebral perfusion pressure (CPP). It has been postulated that when there is a direct relationship between these two factors (index is positive), the cerebrovascular autoregulation is impaired [8]. Zero or negative index signifies intact autoregulation. Mxa is a similar index,derived from the correlation between FV and mean arterial
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