Asymmetric dynamic cerebral autoregulatory response to cyclic stimuli
Asymmetric dynamic cerebral autoregulatory response to cyclic stimuli
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DOI：
10.1161/strokeaha.106.473462
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发表时间：
2007-05-01
期刊：
影响因子：
8.3
通讯作者：
Newell, David W.
中科院分区：
文献类型：
--
作者：
Aaslid, Rune;Blaha, Martin;Newell, David W.
背景和目的-动态脑自动调节被证明是快速有效的，但其机制是否对称尚不清楚，也就是说，与动脉血压的向下突变相比，它对向上具有同等的代偿作用。方法14例颅脑损伤患者和10例正常人进行了双侧经颅多普勒和连续的ABP记录。循环ABP刺激是由大腿袖带产生的，大腿袖带在收缩压以上快速膨胀15秒，然后交替收缩15秒。至少8个这样的周期被集合平均，动态自动调节增益(AG(UP)和AG(DN))分别针对ABP的向上和向下变化进行估计。结果：正常受试者AGdn为0.74+/-0.18，AG(UP)为0.77+/-0.17(平均+/-SD)，差异无统计学意义。AG(DN)和AG(Up)之间的相关性较弱(r=0.24)。在颅脑损伤患者中，AG(DN)为0.30±/-0.21，AG(UP)为1.27+/-0.76，差异有高度显著性(P<；0.001)。AG(DN)与AG(Up)呈负相关(r=-0.33)。脑自动调节指数与AG(DN)呈正相关(r=0.79)，与AG(Up)呈弱负相关(r=-0.47)。它也可能在正常受试者中存在，尽管程度较小。这一发现表明，脑自动调节机制的运行可能存在非线性效应。
Background and Purpose - Dynamic cerebral autoregulation has been shown to be fast and effective, but it is not well known if the mechanism is symmetric, that is to say, it acts with equal compensatory action to upward as compared with downward abrupt changes in arterial blood pressure (ABP).Methods - Fourteen patients with head injuries and 10 normal subjects had bilateral transcranial Doppler and continuous ABP recording. Cyclic ABP stimuli were generated by large thigh cuffs, which were rapidly inflated above systolic pressure for 15 seconds alternating with 15 seconds of deflation. At least 8 such cycles were ensemble-averaged and the dynamic autoregulatory gain (AG(up) and AG(dn)) was estimated separately for upward and downward changes in ABP. The results were compared with the autoregulation index using conventional leg cuff releases.Results - In normal subjects, AGdn was 0.74 +/- 0.18 and AG(up) was 0.77 +/- 0.17 ( mean +/- SD); the difference was insignificant. The correlation between AG(dn) and AG(up), however, was weak ( r = 0.24). In the patients with head injury, AG(dn) was 0.30 +/- 0.21 and AG(up) was 1.27 +/- 0.76, the difference being highly significant ( P < 0.001). There was a negative relationship between AG(dn) and AG(up) ( r = - 0.33). Autoregulation index correlated well with AG(dn) ( r = 0.79) and weakly negatively with AG(up) ( r = - 0.47).Conclusions - A strongly asymmetric dynamic response of the cerebral autoregulation was seen the majority of patients with head injury. It might also have been present, albeit to a lesser degree, in the normal subjects. The findings suggest that nonlinear effects may be present in the operation of the cerebral autoregulation mechanism.