Lewis P M, Rosenfeld J V, Diehl R R, Mehdorn H M, Lang E W
Department of Neurosurgery, The Alfred Hospital, Melbourne, Australia.
Acta Neurochir (Wien). 2008 Feb;150(2):139-46; discussion 146-7. doi: 10.1007/s00701-007-1447-z. Epub 2008 Jan 23.
Impairment of cerebral autoregulation is known to adversely affect outcome following traumatic brain injury (TBI). The phase shift (PS) method of cerebral autoregulation (CA) assessment describes the time lag between fluctuations in arterial blood pressure (ABP) and cerebral blood flow velocity (CBFV) in the middle cerebral artery. An alternative method (Mx-ABP) is based on the statistical correlation between ABP and CBFV waveforms over time. We compared these two indices in a cohort of severely head injured patients undergoing controlled, 6-breaths-per-minute ventilation.
PS and Mx-ABP were calculated from 33 recordings of CBFV and MAP in 22 patients with TBI. Spearman's correlation coefficient was used to assess the agreement between PS and Mx-ABP. The relationship between ICP slow wave amplitude, MAP slow wave amplitude and mean ICP was also examined.
Mean values for Mx-ABP and PS were 0.44 +/- 0.27, and 49 +/- 26 (degrees), respectively. PS correlated significantly with Mx-ABP (r = -0.648, p < 0.001). A Bland-Altman plot of normalised Mx-ABP and Phase Shift values showed no significant bias or relationship (mean difference = 0.0004, r = -0.037, p = 0.852). During the test procedure, ICP fluctuated in an approximately sinusoidal fashion, with a mean amplitude of 4.96 +/- 2.72 mmHg (peak to peak). The magnitude of ICP fluctuation during deep breathing correlated weakly but significantly with mean ICP (r = 0.391, p < 0.05) and with the amplitude of ABP fluctuations (r = 0.625, p < 0.0005).
Phase shift and Mx-ABP in TBI are well correlated. Deep breathing presents as an effective tool with which to assess autoregulation using the phase shift method.
已知脑自动调节功能受损会对创伤性脑损伤（TBI）后的预后产生不利影响。脑自动调节（CA）评估的相移（PS）方法描述了动脉血压（ABP）波动与大脑中动脉脑血流速度（CBFV）波动之间的时间滞后。另一种方法（Mx-ABP）基于ABP和CBFV波形随时间的统计相关性。我们在一组接受每分钟6次呼吸的控制性通气的重度颅脑损伤患者中比较了这两个指标。
从22例TBI患者的33次CBFV和MAP记录中计算PS和Mx-ABP。使用Spearman相关系数评估PS和Mx-ABP之间的一致性。还检查了颅内压慢波幅度、平均动脉压慢波幅度与平均颅内压之间的关系。
Mx-ABP和PS的平均值分别为0.44±0.27和49±26（度）。PS与Mx-ABP显著相关（r = -0.648，p < 0.001）。标准化Mx-ABP和相移值的Bland-Altman图显示无显著偏差或相关性（平均差异 = 0.0004，r = -0.037，p = 0.852）。在测试过程中，颅内压以近似正弦的方式波动，平均幅度为4.96±2.72 mmHg（峰峰值）。深呼吸期间颅内压波动的幅度与平均颅内压呈弱但显著的相关性（r = 0.391，p < 0.05），与动脉血压波动幅度呈显著相关性（r = 0.625，p < 0.0005）。
TBI中的相移和Mx-ABP具有良好的相关性。深呼吸是使用相移方法评估自动调节的有效工具。
