脑血流自动调节功能的三单元模型

目的建立一个三单元集中参数模型来模拟脑血流的自动调节功能。方法根据Bloor的实验数据拟合了一条在脑血流自动调节功能中,反映脑血流量和平均动脉压之间关系的三次曲线,然后利用这一拟合曲线来确定模型中的不定常电阻元件。结果利用这一模型,对不同压力变化情况下的脑血流量变化进行了数值模拟。通过与实验数据进行了对比,发现这一不定常三单元模型能够较为简单地模拟脑血流自动调节功能。结论经过改造的这一三单元集中参数模型可以为脑血流自动调节功能及脑血管疾病的研究提供帮助。     

2260米以上地区经颅多普勒超声脑血流正常值研究

目的：测定２２６０米地区健康人群ＴＣＤ正常参考值。方法：采用ＴＣＤ测定４６１例不同年龄性别世居或移居２２６０￣３８００米地区５年以上健康人颅底动脉血流速度。结果：各动脉血流速度以ＭＣＡ为最高，顺序ＭＣＡ〉ＡＣＡ〉ＢＡ〉ＶＡ〉ＰＣＡ。各动脉血流速度随年龄递减（Ｐ〈０．０１），其差率与国内外报告基本相同。脑血流速度ＭＣＡ的Ｖｄ，ＢＡ、ＶＡ的各期血流速度女性高于男性；ＰＩ偏低，ＰＩ、ＲＩ６０岁前男高于女     

颈动脉硬化的彩超表现与中风

目的：探讨颈动脉粥样硬化的好发部位、狭窄程度及与脑梗塞的关系。方法：对150例脑梗塞患者进行颈动脉超声检查，了解有无斑块形成及颈动脉狭窄程度。结果：150例中发现存在不同程度的颈动脉粥样斑块108例，斑块好部位依次为颈动脉分叉部(47．71％)、颈总动脉(39．45％)和颈内动脉(12．84％)。结论：颈动脉超声检查可早期发现颈动脉粥样硬化；颈动脉粥样斑块与脑梗塞有密切的相关性.     

上矢状窦引流桥静脉的彩色多普勒超声观察

目的：通过对上矢状窦引流桥静脉的彩色多普勒超声观察,为脑静脉血流动力学研究提供新的参考数据。方法：选择20例神经外科开颅术后1年的患者,经术后骨窗彩超观测上矢状窦引流桥静脉。结果：桥静脉呈节段性集中分布,分为前段组和后段组两组。前段组桥静脉数目为(3.1±1.4) 支,直径为(2.7±0.7) mm,注入角度为(96±33) °,平均血流速度为(10.0±2.8) cm/s。后段组桥静脉数目为(5.8±1.0) 支,直径为(3.2±1.2) mm,注入角度为(41±24) °,平均血流速度为(11.4±2.8) cm/s。与前段组相比较,后段组桥静脉的数目较多,直径较大,注入角度较小,血流速度较快。结论：彩色多普勒超声通过术后骨窗能够观测到上矢状窦引流桥静脉的形态和血流速度,为脑静脉血流动力学研究提供了新的参考数据,并为神经外科术后监测提供了新的方法。     

高血压患者脑血流动力学改变特征的MRI研究

目的：利用磁共振（MR）灌注成像（PWI）结合乙酰唑胺（ACZ）负荷试验评估高血压患者脑血流动力学改变的特征。方法:对13例无血管狭窄的高血压患者和12例正常对照在口服乙酰唑胺前后进行常规MR检查和PWI检查，测量两组受检者双侧尾状核、豆状核、额上回、颞上回、丘脑和楔叶的血流平均通过时间（MTT）、局部脑血容量（rCBV）并计算局部脑血流量（rCBF）后进行比较。结果:（1）ACZ负荷前：高血压组双侧尾状核、额上回、颞上回、丘脑和楔叶的MTT短于正常对照组（P＜0．05），但豆状核的MTT与对照组比较无显著差异；两组受检者各兴趣区（ROI）的rCBV及rCBF无显著差异；（2）ACZ负荷后：高血压组豆状核的MTT长于对照组（P＜0．05），其余各ROI的MTT相比较无显著差异；两组受检者各ROI的rCBV及rCBF之间无统计学差异。结论:高血压患者在发生血管狭窄之前，其脑血流动力学已经发生改变，而且各部位的改变程度不一致，豆状核可能是血液动力学改变发生最早的部位之一。     

癫痫患者脑血流速度改变与癫痫灶定侧的关系

目的：探讨癫痫发作间期脑血流变化对癫痫灶定侧的价值。方法：47例癫痫病人发作间期行经颅多普勒超声脑血流速度测定．并与临床、脑电图定位和MRI／CT病灶对比分析。结果：根据临床症状确定病灶侧的19例病人中。病灶侧脑血流速度改变(升高和降低)的比率显著高于双侧脑血流速度对称者；在脑电图确定病灶侧的24例病人中，病灶侧脑血流速度升高比率显著高于脑血流速度降低和双侧脑血流速度对称者；在MRI确定病灶侧的13例病人中，病灶侧脑血流速度增快7例，减慢2例，双侧血流速度对称4例。结论：癫痫病人一侧脑血流速度增高，高度提示癫痫病灶侧。     

内皮素与血压调节：高血压的内皮素机制研究

内皮素endothelin是Yanagisawa等于1988年从培养的猪主动脉内皮细胞中分离、纯化出的一种活性多肽,具有强烈收缩血管、加强心肌收缩力、促进神经内分泌等作用,对     

小型幼猪体外循环模型灌注流量对脑血流灌注的影响

目的建立幼猪体外循环(cardiopulmonary bypass,CPB)模型,观察CPB灌注流量发生改变期间,脑灌注流量和局部脑氧饱和度(regional cerebral oxygen saturation,rSO_2)的变化,从而探索CPB灌注流量对脑血流量自我调节的影响,以期为婴幼儿CPB合理的灌注管理、预防脑缺血提供理论依据。方法 12只幼猪按照随机表分为3组,对照组、高流量组(H组)、低流量组(L组)。建立单泵双管CPB灌注模型,用血流检测仪直接检测灌注管路流量反映不同流量下脑动脉内血液灌注的变化,并采用近红外分光广度检测技术(near infrared reflectance spectroscopy,NIRS)监测幼猪CPB模型中rSO_2的变化。在CPB开始前10 min、CPB开始后10 min、升主动脉阻断后30 min和升主动脉开放后10 min 4个时间点检测血清S100钙结合蛋白B(S100 B)浓度。分别进行苏木精-伊红(HE)染色、尼氏染色观察海马CA区组织学变化。结果在主动脉阻断期间,H组脑灌注流量[(30.8±9.9)mL/(kg·min)]较L组[(19.0±7.4)mL/(kg·min)]有增高趋势但无统计学差异(P=0.072),且该时间点H组rSO_2值(52.65%±3.1%)显著高于L组(47.3%±3.3%)(P0.05)。海马组织学变化及血清S100 B蛋白水平无组间差异。结论在小型猪体外循环灌注模型中,脑动脉内流量及局部脑氧饱和度监测提示脑血流压力/血流自我调节减弱,高流量组脑灌注效果优于低流量灌注。     

脑性瘫痪患儿脑血流动力学变化的研究

目的　研究脑性瘫痪患儿脑血流速度的变化。方法应用彩色多普勒超声对 5 5例脑性瘫痪儿检测脑血流参数 ,并与 4 0例正常小儿进行对照检测。结果　脑性瘫痪儿三个年龄段的大脑前动脉及大脑中动脉脑血流速度较同年龄段正常儿都有程度不一的减少。对于大脑前动脉 ,1岁以前的脑瘫患儿的舒张末血流速度 (Vd)、时间平均流速 (Vm)及 6个月以后收缩期峰值流速 (Vs)明显减少 (P <0 0 5 ) ,而 1岁以后的患儿血液动力Vm、Vd的变化更为显著 (P <0 0 1) ,并且各年龄段的脑血流阻力RI都有明显的增加 (P <0 0 5 )。对于大脑中动脉 ,6个月以内的患儿Vd、Vm减少明显 (P <0 0 5 ) ,到 6个月以后患儿的Vd、Vm变化更为显著 (P <0 0 1) ,同时 ,患儿的脑血流阻力的增加也随年龄的增加而变化越发显著 ,6个月以后的患儿的RI已有明显增加 (P <0 0 5 ) ,1岁以后的患儿增加更为显著 (P <0 0 1)。结论　脑性瘫痪儿脑血供减少 ,且随着年龄的增长患儿脑供血不足更趋显著 ,早期干预脑性瘫痪儿可改善预后。检测脑血流可有助于脑性瘫痪儿的早期诊断及治疗。     

导纳式双侧脑血流自动检测仪的研制

传统脑血流检测仪采用阻抗原理仅能描记脑阻抗波形，进行人工分析波形和几个参数的计算，由于波幅值受基础阻抗Ｚ０ 的影响导致重复性很差，远不能满足临床需求。我们研制开发的导纳式双侧脑血流自动检测仪即消除了Ｚ０ 的影响又可对二维脑导纳微分环的形态、面积大小及各相面积比值进行自动分析计算。据此可反映出颈内动脉颅内段和椎动脉的血管流量以及静脉回流阻力等定量指标。尤其采用了导纳频谱分析技术可对波形的改变进行定量分析，从而大大提高了该检测方法的临床应用价值。     

Effects of enalapril on cerebral blood flow and its autoregulation in hypertensive rats

The lower limit of cerebral blood flow autoregulation was shifted to a higher blood pressure in rats with renal and spontaneous hypertension. Enalapril decreased blood pressure and vascular resistance in the brain, stabilized cerebral blood flow, and potentiated autoregulatory response of cerebral vessels to blood pressure drop. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 127, No. 6, pp. 642–644, June, 1999     

Effects of alpha- and beta-adrenergic blockers on the lower limits of cerebral blood flow autoregulation in spontaneously hypertensive rats

The effects of alpha- and beta-adrenergic blockers (phenoxybenzamine, PBZ and propranolol, PPL, respectively) on the cerebral (CBF) and cerebellar (CeBF) blood flow autoregulations were examined in spontaneously hypertensive rats. CBF and CeBF were measured during stepwise hemorrhagic hypotension using hydrogen clearance method. The lower limits of autoregulation for CBF beyond which blood flow was decreased steeply were 72% of the resting blood pressure level in the control, 56% in the PBZ treated group, and 80% in the PPL group. Similar tendency was observed in CeBF. These results indicate that PBZ leads to a downward shift while PPL to a slight upward shift of the lower limits of CBF and CeBF autoregulations, suggesting that alpha-adrenergic blockade has a favorable effect for the maintenance of cerebral blood flow during acute reduction of blood pressure.     

Laser Doppler flowmetry is valid for measurement of cerebral blood flow autoregulation lower limit in rats

Laser Doppler flowmetry (LDF) is a recent technique that is increasingly being used to monitor relative changes in cerebral blood flow whereas the intra-arterial 133xenon injection technique is a well-established method for repeated absolute measurements of cerebral blood flow. The aim of this study was to validate LDF for assessment of cerebral autoregulation and CO2 reactivity with the 133xenon injection technique as the gold standard. Simultaneous measurements of cerebral blood flow (CBF) were collected by LDF (CBF(LDF)) and the 133xenon method (CBF(Xe)) while (1) cerebral autoregulation was challenged by controlled systemic haemorrhage, or (2) cerebral blood flow was varied by manipulating the arterial partial pressure of CO2 (P(a,CO2)). LDF slightly overestimated CBF under conditions of haemorrhagic shock and haemodilution caused by controlled haemorrhage (paired t test, P < 0.05). However for pooled data, the autoregulation lower limit was similar when determined with the 133xenon and the LDF techniques: 65 +/- 3.9 mmHg and 60 +/- 5.6 mmHg, respectively. Linear regression analysis yielded CBF(Xe) = (1.02 x CBF(LDF)) + 9.1 and r = 0.90. Even for substantial changes in P(a,CO2), the two methods resulted in similar results. We conclude that even though LDF overestimated CBF during haemorrhagic shock caused by controlled haemorrhage, the lower limit autoregulation was correctly identified. The laser Doppler technique provides a reliable method for detection of a wide range of cerebral blood flow changes under CO2 challenge. Haemodilution influences the two methods differently causing relative overestimation of blood flow by the laser Doppler technique compared to the 1(33)xenon method.     

The role of adenosine in autoregulation of cerebral blood flow

We have investigated the role of adenosine, a purine nucleoside and potent vasodilator of cerebral pial vessels, during both acute (0–60 sec) and sustained (2–5 min) changes in cerebral perfusion pressure. Brain adenosine concentrations are rapidly increased within 5 sec of the onset of systemic hypotension and parallel, in a temporal fashion, the changes in pial vessel diameter and alterations in cerebral vascular resistance. During sustained hypotension, brain levels of adenosine are increased even within the autoregulatory range. These data are constant with the hypothesis that adenosine is an important metabolic factor in cerebral autoregulation.     

Cognitive performance and cerebral blood flow in essential hypotension

In the present study cerebral blood flow was assessed in 40 subjects with chronically low blood pressure and 40 normotensive controls at resting conditions and during the execution of a cued reaction time task. Blood flow velocities were recorded by means of transcranial Doppler sonography in both middle cerebral arteries. In hypotensives flow velocity at rest was reduced bilaterally. During the anticipation of the stimuli, which the subjects had to respond to, a predominantly right hemispheric increase of flow velocity was observed in both groups. This increase was significantly less pronounced in the hypotensive group. Hypotensives showed longer reaction times, and there was a negative correlation between the extent of the flow velocity increase and the reaction times. This study is the first to demonstrate a reduced cerebral perfusion and maladaption of blood flow to cognitive demands due to essential hypotension.     

Changes in carotid blood flow and electrocardiogram in humans during and after walking on a treadmill

Blood flow velocity in the common carotid artery and the electrocardiogram were measured simultaneously by telemetry in seven male subjects during 20-min walking on a treadmill at an exercise intensity corresponding to a mean oxygen uptake of 26.0 (SD 2.9) ml · kg ^–1 · min ^–1. The mean cardiac cycle was shortened from 0.814 (SD 0.103) s to 0.452 (SD 0.054) s during this exercise. Of this shortening, 73% was due to shortening of the diastolic period and 27% to shortening of the systolic period. In the relatively small shortening of the mean systolic period [from 0.377 (SD 0.043) s to 0.268 (SD 0.029) s], the isovolumetric contraction time was shortened by 56%. During exercise, the heart rate (f _c) increased by 79.4% [from 74.3 (SD 9.3) beats · min ^–1 to 133.3 (SD 14.8) beats · min ^–1], and the peak blood velocity (S₁) in the common carotid artery increased by 56.1% [from 0.82 (SD 0.10) m · s^–1 to 1.28 (SD 0.11) m · s^–1]. After exercise, the S₁ decreased rapidly to the resting level. The f _c decreased more slowly, still being higher than the initial resting level 5 min after exercise. The diastolic velocity wave and the end-diastolic foot decreased during exercise. The blood flow rate in the carotid artery increased transiently by 13.5% at the beginning of exercise [from 5.62 (SD 0.63) ml · s^–1 to 6.38 (SD 0.85) ml · s^–1] and by 26.5% at the end of the exercise period [from 5.62 (SD 0.63) ml · s^–1 to 7.11 (SD 1.34) ml · s^–1]. The increase of blood flow in the carotid artery at the onset of exercise may have been mainly related to cerebral activation, and partly to an increase of blood flow to the skin of the head. The physiological significance for cerebral function of the increase of blood flow in the artery after the end of exercise is unknown.     

An on-line system for acquisition and processing of cerebral blood flow data

Regional cerebral blood flow is measured by monitoring the clearance from the brain of the gamma emitting radioisotope ¹³³Xe following an intracarotid artery bolus injection. On-line data analysis, which is performed on a PDP $\text{12}\text{30}$ digital computer, involves exponential stripping to isolate grey and white matter flows and integration of the clearance curves to infinity to enable the mean flow to be calculated. The data is displayed in real time and stored on the PDP 12 Linc tapes as a permanent record.     

Assessment of cerebral autoregulation using time-domain cross-correlation analysis

Time domain cross-correlation analysis of pre-filtered mean arterial blood pressure (MABP) and mean cerebral blood flow velocity (MCBFV) was applied to assess the cerebral autoregulation (CA). Beat-to-beat time series of spontaneous arterial blood pressure and cerebral blood flow velocity were obtained from 13 young normal volunteers with the Finapres device and the transcranial Doppler for periods of approximately 5 min in the supine position. Cross-correlation functions (CCFs) were estimated using a 64 beat wide moving window. Mean CCF patterns were obtained for each subject and for the entire population. The MABP and MCBFV signals were bandpass filtered in the very low-frequency range (VLF, 0.015–0.07 Hz), low-frequency range (LF, 0.07–0.15 Hz) and high-frequency range (HF, 0.15–0.40 Hz) before applying CCF for the purpose of studying the effect of different bandwidths on the resulting mean CCFs. Results revealed that the corresponding time lags of the peak values of the MABP–MCBFV CCFs increased significantly between the LF and HF frequency ranges (LF: −1.20±0.91 s, HF: −0.07±0.42 s, p<0.001; paired sign test). The left-shift (negative lag) of the CCF peak between MABP and MCBFV is a result of the phase-lead property. The increasing time lag of the CCF peak indicated evidence of the autoregulatory disturbance. The CCF of pre-filtered spontaneous MABP and MCBFV could be a useful tool to estimate the CA dynamic response.     

Deficient adjustment of cerebral blood flow to cognitive activity due to chronically low blood pressure

The present study aimed to investigate aberrances in the adjustment of cerebral blood flow to cognitive activity due to chronically low blood pressure. By means of transcranial Doppler sonography blood flow velocities in both middle cerebral arteries (MCA) were recorded during the execution of a serial subtraction task in 40 subjects with constitutional hypotension and 40 normotensive control persons. Additionally, blood pressure was continuously monitored. As a main result significant correlations between the task-induced changes in blood pressure and those in MCA blood flow velocities were found in hypotensives, but not in control subjects. The dependence of the regulation of cerebral blood flow on blood pressure points towards deficits in cerebral autoregulation in hypotension. Over the total sample the extent of the task-induced MCA flow velocity increase was positively related to cognitive performance. This underlines the importance of the adjustment of cerebral blood flow to current demands for optimal cognitive functioning.