Institute of Neuroscience, the Second Affiliated Hospital, Guangzhou Medical University, Guangzhou, P.R. China.
Ultrasound Med Biol. 2012 Jul;38(7):1244-50. doi: 10.1016/j.ultrasmedbio.2012.03.006. Epub 2012 Apr 13.
The aim of present study was to validate the assessment of lower limit of cerebral autoregulation (LLCA) as derived from mean artery blood pressure (MABP) and cerebral zero flow pressure (ZFP) by means of transcranial Doppler (TCD) and to determine the accurate relationship between LLCA and MABP in stroke-prone renovascular hypertensive rats (RHRSP). We studied two groups of rats: RHRSP and normal controls. Blood flow velocity of middle cerebral artery was monitored by TCD and arterial blood pressure was recorded in right femoral artery to compute the ZFP. The value of LLCA was determined as the difference between MABP and ZFP and validated by the value determined by blood withdrawal-induced cerebral autoregulation. In normal rats, the LLCA derived from the new method was 69.8 ± 8.7 mm Hg, from the change of blood velocity was 69.4 ± 9.8 mmHg and from blood volume flow after blood withdrawal was 68.8 ± 9.7 mmHg. In the RHRSP group, the corresponding values of LLCA were 109.1 ± 17.2 mm Hg, 110.0 ± 18.0 mm Hg and 109.0 ± 19.3 mm Hg, respectively. In each group, there was no statistically significant difference among the three values. LLCA in RHRSP began to increase 6 weeks after hypertension-induced operation, significantly higher than controls (p < 0.05), and stabilized at 110 mm Hg, 10 weeks after operation. The increase of LLCA was positively correlated with MABP, following an "S" curve, demonstrating that the change of LLCA was more obvious in the middle range of MABP in RHRSP (R(2) = 0.8848, p < 0.05). In conclusion, TCD is a valid and noninvasive method for determination of LLCA compared with the classic method in rats. Our data demonstrated that the change of LLCA may be correlated with MABP, following an "S" curve relationship.
本研究旨在验证通过经颅多普勒（TCD）从平均动脉压（MABP）和脑零血流压（ZFP）推导得出的脑自动调节下限（LLCA）的评估，并确定中风易发性肾血管性高血压大鼠（RHRSP）中 LLCA 与 MABP 之间的准确关系。我们研究了两组大鼠：RHRSP 和正常对照组。通过 TCD 监测大脑中动脉的血流速度，并通过右股动脉记录动脉血压以计算 ZFP。LLCA 的值被确定为 MABP 和 ZFP 之间的差值，并通过通过抽血诱导的脑自动调节确定的值进行验证。在正常大鼠中，新方法得出的 LLCA 值为 69.8 ± 8.7mmHg，从血流速度变化得出的 LLCA 值为 69.4 ± 9.8mmHg，从抽血后血流量得出的 LLCA 值为 68.8 ± 9.7mmHg。在 RHRSP 组中，相应的 LLCA 值分别为 109.1 ± 17.2mmHg、110.0 ± 18.0mmHg 和 109.0 ± 19.3mmHg。在每组中，这三个值之间没有统计学上的显著差异。在高血压诱导手术后 6 周，RHRSP 中的 LLCA 开始增加，明显高于对照组（p<0.05），并在手术后 10 周稳定在 110mmHg。LLCA 的增加与 MABP 呈正相关，呈“S”曲线，表明在 RHRSP 中 MABP 的中间范围，LLCA 的变化更为明显（R²=0.8848，p<0.05）。总之，与经典方法相比，TCD 是一种有效的、非侵入性的确定大鼠 LLCA 的方法。我们的数据表明，LLCA 的变化可能与 MABP 相关，呈“S”曲线关系。
