Müller M, Bianchi O, Erülkü S, Stock C, Schwerdtfeger K
Department of Neurology, Saarland University Hospital, Homburg/Saar, Germany.
Stroke. 2003 May;34(5):1197-202. doi: 10.1161/01.STR.0000068409.81859.C5. Epub 2003 Apr 3.
We sought to describe the dynamic changes in the cerebrovascular system after traumatic brain injury by transfer function estimation and coherence.
In 42 healthy volunteers (mean+/-SD age, 37+/-17 years; range, 17 to 65 years), spontaneous fluctuations of middle cerebral artery blood flow velocity and of finger blood pressure (BP) were simultaneously recorded over a period of 10 minutes under normocapnic and hypocapnic conditions to generate normative spectra of coherence, phase shift, and gain over the frequency range of 0 to 0.25 Hz. Similar recordings were performed in 24 patients with severe traumatic brain injury (Glasgow Coma Scale score <or=8; mean+/-SD age, 50+/-20 years) serially on days 1, 3, 5, and 8 after trauma. Cranial perfusion pressure was kept at >70 mm Hg. Each blood flow velocity/BP recording was related to the presence or absence of middle cerebral artery territory brain parenchyma lesions on cranial CT performed within a close time frame.
In controls, hypocapnia decreased coherence (0.0 to 0.20 Hz), increased phase shift (0.0 to 0.17 Hz), and decreased gain in the frequency range of 0.0 to 0.11 Hz but increased gain at frequencies of 0.20 to 0.25 Hz (P<0.01 for all frequency ranges reported). In patients with traumatic brain injury, 102 investigations were possible. Compared with controls, coherence was increased in the frequency range <0.03 Hz and between 0.13 and 0.25 Hz in both normocapnia and hypocapnia, irrespective of the CT findings. Gain was unchanged in normocapnia and in the absence of a CT lesion. Gain was decreased in hypocapnia at frequencies >0.12 Hz irrespective of the presence/absence of a CT lesion. Phase shift decreased rapidly between 0.06 and 0.13 Hz under hypocapnic conditions and under normocapnic conditions in the presence of a CT lesion (P< 0.01).
Use of spontaneous fluctuations of blood flow velocity and BP to assess the cerebrovascular system dynamically requires consideration of the Paco2 level. In different conditions, including severe traumatic brain injury, the cerebrovascular system behaves linearly only in parts of the investigated frequency range.
我们试图通过传递函数估计和相干性来描述创伤性脑损伤后脑血管系统的动态变化。
在42名健康志愿者（平均±标准差年龄，37±17岁；范围，17至65岁）中，在正常碳酸血症和低碳酸血症条件下，同时记录大脑中动脉血流速度和手指血压（BP）的自发波动10分钟，以生成0至0.25赫兹频率范围内相干性、相移和增益的标准频谱。在24名重度创伤性脑损伤患者（格拉斯哥昏迷量表评分≤8；平均±标准差年龄，50±20岁）中，在创伤后第1、3、5和8天连续进行类似记录。颅内灌注压保持在>70毫米汞柱。每次血流速度/BP记录都与在相近时间内进行的头颅CT上大脑中动脉区域脑实质病变的有无相关。
在对照组中，低碳酸血症降低了相干性（0.0至0.20赫兹），增加了相移（0.0至0.17赫兹），并在0.0至0.11赫兹频率范围内降低了增益，但在0.20至0.25赫兹频率处增加了增益（所有报告的频率范围P<0.01）。在创伤性脑损伤患者中，进行了102次检查。与对照组相比，无论CT结果如何，在正常碳酸血症和低碳酸血症中，<0.03赫兹频率范围以及0.13至0.25赫兹频率范围内的相干性均增加。在正常碳酸血症且无CT病变时，增益不变。无论有无CT病变，在低碳酸血症中，>0.12赫兹频率处的增益均降低。在低碳酸血症条件下以及存在CT病变的正常碳酸血症条件下，相移在0.06至0.13赫兹之间迅速降低（P<0.01）。
利用血流速度和BP的自发波动动态评估脑血管系统需要考虑动脉血二氧化碳分压水平。在不同条件下，包括重度创伤性脑损伤，脑血管系统仅在部分研究频率范围内呈线性表现。
