短暂性脑缺血发作病人脑循环中微栓子信号与脑卒中的危险性研究

目的 对短暂性脑缺血发作（TIAs)病人观察脑循环微栓子信号（MES）发生率及其发生脑卒中的危险率。方法 用经颅多普勒（TCD）监测TIAs病人双侧大脑中动脉（MCA）微栓子信号（MES）,并跟踪观察12个月。结果 25例短暂脑缺血发作病人有5例记录到MES（阳性率20％）,跟踪观察12个月,5例MES阳性病例中的3例（60％）发生脑梗死;而20例未记录到MES的病人中,仅有2例（10％）发展为脑梗死。结论 可检测到MES的TIAs病人发生梗死的危险性比无MES病人高。     

大鼠脑微栓塞模型的建立

目的建立重复性好、稳定性高的大鼠脑微栓塞模型,为研究微栓子引起的神经细胞缺血性损害提供依据。方法54只SD大鼠随机分为假手术组(10只)和动脉粥样硬化斑块微栓塞模型组(44只),后者又按微栓子的大小分为106~150μm组(20只)、75~105μm组(12只)和55~74μm组(12只)。在手术显微镜下将静脉留置针外套管从颈外动脉逆行插管至颈内动脉,注入相应大小的动脉粥样硬化斑块微栓子,100个/只。24 h后处死大鼠,采用HE染色、原位缺口末端标记(TUNEL)法及Caspase-3蛋白免疫组化染色观察神经细胞缺血性损伤程度。结果假手术组大鼠脑组织病理切片均未发现梗死灶。在106~150μm组、75~105μm组和55~74μm组中,大鼠脑梗死灶出现的比例分别为15/17、11/12和5/12;TUNEL阳性细胞数分别为(33.3±10.9)、(25.9±9.7)和(18.0±6.9)个/HP,明显高于假手术组的(5.7±2.7)个/HP(均P<0.01);Caspase-3阳性细胞数分别为(67±11)、(59±12)和(46±11)个/HP,明显高于假手术组的(7.8±3.1)个/HP(均P<0.01)。结论55~150μm的动脉粥样硬化斑块微栓子能稳定地造成大鼠脑组织微梗死或神经细胞凋亡。     

A high blood level in the air trap reduces microemboli during hemodialysis

Previous studies have demonstrated the presence of air microemboli in the dialysis circuit and in the venous circulation of the patients during hemodialysis. In vitro studies indicate that a high blood level in the venous air trap reduces the extent of microbubble formation. The purpose of this study was to examine whether air microbubbles can be detected in the patient's access and if so, whether the degree of microbubble formation can be altered by changing the blood level in the venous air trap. This was a randomized, double‐blinded, interventional study of 20 chronic hemodialysis patients. The patients were assigned to hemodialysis with either an elevated or a low blood level in the air trap. The investigator and the patient were blinded to the settings. The numbers of microbubbles were measured at the site of the arteriovenous (AV) access for 2 min with the aid of an ultrasonic Doppler device. The blood level in the air trap was then altered to the opposite setting and a new measurement was carried out after an equilibration period of 30 min. Median (range) for the number of microbubbles measured with the high air trap level and the low air trap level in AV access was 2.5 (0–80) compared with 17.5 (0–77), respectively (P = 0.044). The degree of microbubble formation in hemodialysis patients with AV access was reduced significantly if the blood level in the air trap was kept high. The exposure of potentially harmful air microbubbles was thereby significantly reduced. This measure can be performed with no additional healthcare cost.     

Analysis of index modulation of doppler microembolic signals part II: in vitro discrimination

The purpose of this study was to validate through experiments that frequency modulation (FM) of microembolic signatures was principally due to the radiation force. Several experiments were required to prove that such a frequency modulation originates from microdisplacements induced by the radiation force acting on microbubbles. The first experiment was performed to verify that the diffraction effects due to the presence of a skull did not disturb the acoustic field appreciably and to validate that a radiation force in the brain was sufficient to create a detectable microdisplacement. A second in vitro experiment using a single gate transcranial Doppler (TCD) system was conducted to show discrimination feasibility and to check that microembolic frequency modulation signatures (FMS) and frequency modulation index (FMI) were the same as those observed in vivo and those calculated by simulation. A final in vitro experiment was performed using a multigate multichannel TCD system to confirm the second experiment by directly measuring the microdisplacement induced by the radiation force. A new parameter, to be known as the position modulation index (PMI), is proposed. We showed that the radiation force is sufficient to induce detectable microdisplacements despite the presence of the skull. We also showed that the diffraction effects due to the skull induced a decrease in the ultrasound beam of 7.6 dB. Finally, we showed by using FMI and PMI that it is possible to discriminate gaseous from formed elements (<100 microns) despite the presence of the skull. The discrimination based on the FMI is an off-line technique allowing the analysis of standard TCD recordings. However, discrimination based on the PMI requires recordings obtained exclusively from a multi-gate system. (E-mail: jean-marc.girault@univ-tours.fr)     

N-tert-butyl-α-phenylnitrone reduces the number of microinfarctions in the rabbit brain cortex

Dementia due to cerebral ischemic lesions is relatively common in the elderly. Since many of these lesions are probably caused by emboli, studying emboli-induced cerebral lesions in rabbits should, hopefully, provide information that is useful when searching for a means of preventing and treating vascular dementia in humans. Using magnetic resonance imaging we have found that N-tert-butyl-α-phenyl-nitrone (a free radical scavenger) reduced the number of emboli-induced cerebral microinfarctions in the rabbit cortex but did not have any impact on the number of infarctions found in the subcortical structures. The results suggest that significant amount of free radicals are produced in the ischemic foci located in the cortex, but not in the ischemic foci located in the subcortical structures. This finding may be of importance when considering treatments for cerebral ischemia in humans. Received: 20 January 1998 / Accepted: 7 October 1998     

TCD对无症状性颈动脉狭窄患者微栓子检测的临床研究

目的应用经颅多普勒(TCD)检查微栓子以识别无症状性(ACS)颈动脉狭窄患者中需要治疗的高危患者。方法收集本院神经内科常规体检人员,经多普勒超声检查发现颈动脉狭窄≥50%,而未发生缺血症状或至少在12个月内无症状者,应用TCD检查微栓子,每月1次,连续随访2a。结果入选213例患者,23例(10.8%)初次检查发现微栓子(TCD+),190例(89.2%)没有发现微栓子(TCD-)。随访1a,TCD+组2例(17.4%)发生卒中,而TCD-组5例(2.6%)发生卒中;2a时TCD+组1例(4.5%)发生卒中,TCD-组3例(1.6%)发生卒中。结论对无症状性颈动脉狭窄患者,TCD检查微栓子阳性者卒中发病率高,应给予药物或相应的手术治疗,预防卒中发生。     

基于中医症征积分探讨益气活血方调节微栓子对急性缺血性脑卒中患者生活质量的影响

目的:通过随机、对照的研究方法,运用中风中医症征积分量表客观地评价益气活血颗粒对急性缺血性卒中(AIS)并微栓子(MES)阳性的患者生活质量的影响。方法:将120例AIS患者分为益气活血颗粒试验组和安慰剂对照组,每组各60例。试验组在单纯西医常规治疗的基础上,给予益气活血颗粒联合西药为一体的中西医结合综合治疗方案; 对照组为西医常规治疗,疗程为14 d,客观评价中西医结合综合方案可明显缓解AIS患者中医症状的临床表征以及对患者个体日常生活能力改善的临床疗效。结果:益气活血颗粒在改善AIS患者中医症状积分及临床症状对日常生活影响程度积分方面明显优于对照组(P<0.05)。结论:益气活血颗粒能明显减少AIS患者颅内MES数目,有效改善患者的中医症征积分,并可能因此而改善患者的临床症状使其获益,此种中西医结合治疗AIS的方法值得应用。     

经颅多普勒应用于脑循环中微栓子监测方法学探讨

目的探讨经颅多普勒检测技术进行脑循环中微栓子(MES)监测的方法及其影响因素。方法采用德国DWL公司multi-DopX4TCD仪,对100例患者脑循环中微栓子监测。结果微栓子监测阈值设定在9dB时,其检出个数与3dB及6dB差异有显著性(P<0.05);选择30min的监测时间,微栓子检出个数与15min组比较,差异有显著性(P<0.05)。结论脑循环中微栓子监测选用9dB的阈值,15～30min的监测时间,可以有效的检出其存在。     

An ultrasonic detector for microgasemboli in a bloodflow line

A detector for small gas bubbles in the blood-flow line from a heart-lung machine was constructed and tested. The way in which a passing bubble forms a signal is analyzed. The relation between signal size and bubble size is established experimentally and confirmed by theoretical calculations. It is shown that solid and soft (tissuelike) particles give much smaller signals than gaseous particles. The influence of the measuring frequency on the detectability of particles is derived from theory and shown experimentally.