脑组织氧分压监测技术的研究与应用进展

脑组织氧分压（brain tissue oxygen partial pressure,PbtiO2) 技术是进入90年代后逐渐成熟起来的脑氧代谢监测方法,与传统的脑氧监测方法相比具有微创,安全,准确的特点,应用这一技术可以对病人进行术中及术后的长期,动态监测,有助于正确判断脑血流量,颅内压,脑灌注压之间的关系,早期判断预后,但脑组织氧分压监测所获得的信息尚需结合其他监测手段获得的数据加以综合分析,才能得出准确结论。     

手术治疗急性重型颅脑损伤患者的意义及其脑组织氧分压变化

目的探求手术治疗重型颅脑损伤患者脑组织氧分压（PbtO2）变化的临床意义。方法对42例急性重型脑损伤患者（均在全麻下急诊行血肿清除术和/或去骨瓣减压术）,并且符合GCS≤8分,术前以及术后行PbtO2持续监测,同时行血电解质、动脉血氧分压（PaO2）、动脉血二氧化碳分压（PcaO2）测定;分析PbtO2变化的临床意义。结果预后良好及预后不良组经过手术的干预,8、24、48、72h后PbtO2均明显升高,与术前相比差异有统计学意义（P〈0.05）;而在预后死亡组中,术后8、24、48hPbtO2与术前相比差异均无统计学意义（P〉0.05）。没有发生与插入监测电极相关的并发症。结论脑组织氧分压测定是一种安全、灵敏、可靠的局部脑组织氧监测方法,可反映出重型脑损伤后的脑组织缺血缺氧情况,对临床治疗具有重要的指导作用。持续脑组织氧分压监测可判断重型脑外伤患者预后。     

应用高压氧治疗的护理体会

目的高压氧可以提高血液和组织的氧张力,增加血氧含量。方法给予常规神经营养、镇痛、止痛、活血、调节植物神经功能的神经外科常规处理和综合治疗。结果使脑组织脑脊液的氧分压相应地提高,增加脑组织氧的弥散距离,组织的储氧量增加,氧的扩散范围扩大,促进脑侧支循环的建立和疏通微循环。结论同时高压氧对血管的直接刺激作用可引起血管收缩,使颅内压降低、从而改善脑循环和脑组织的供养,使受损的神经组织重新获得丰富的氧供和营养,使脑组织的能量代谢得到改善,加速受损的脑组织的修复和脑功能的恢复。     

三维图像融合技术在有创脑电监测中的应用

 摘要 确认颅内电极置入的位置是否正确。方法：9例定位困难的癫痫患者,实施了颅内电极置入术。术前行头部MRI导航定位相扫描,术后行头部CT薄扫。将CT和MRI影像进行三维融合,在重建的图像上标记电极点的位置。结果：获得了颅内电极和脑组织关系的三维立体图像,可以清晰地判断电极位置,并为皮层功能定位（Mapping）和设计手术计划提供了直观的影像学资料。 结论：三维融合技术在有创脑电监测中可以确认电极触点和脑组织之间的准确位置关系。     

近红外分光仪在小儿体外循环中的应用

目的 探讨小儿体外循环中,近红外分光仪(NIRS)在监测脑氧合功能方面的价值.方法 心内直视手术病人24例,随机平均分为两组:中度低温体外循环(MHCPB)组(n=12) 和深低温停循环(DHCA)组(n=12),NIRS连续监测脑组织氧合血红蛋白(cere-HbO2),CPB开始、降温末、复温末以及术后6小时四个时点分别测定颈静脉球血测定乳酸值(Lact)和特异性神经源性烯醇化酶( NSE),术前、术后脑电图(EEG)检查各一次,并进行相关分析.结果 MHCPB组中,无脑电图异常,cere-HbO2指标变化不大,与生化指标也无显著相关;DHCA组中,两例患儿术后出现异常脑电图,cere-HbO2指标在停循环开始便显著下降,下降幅度和持续时间与复温末Lact及NSE值显著相关.结论 DHCA中,cere-HbO2与反映脑损害的其它指标显著相关,NIRS是一种崭新的,无创的脑氧合监测方法.     

体外循环围术期胃肠道粘膜PH监测

胃肠粘膜内pH(pHi)监测具有无创性,特异度及灵敏度高的特点,是判断早期组织氧摄取和氧利用能力的方便方法,也是了解胃肠道粘膜血供的特异性监测手段。pHi在体外循环(CPB)围术期的监测反映了CPB中胃肠道的病理生理变化,pHi的下降值与胃肠道损伤程度呈负相关。胃肠道pHi的监测对判断CPB病人的病情、预测术后并发症和死亡率具有重要的指导意义。     

脑电地形图在脑组织移植治疗顽固性癫痫术中的应用

应用病灶切除并胎脑组织移植术为１３例顽固性癫痫患儿进行治疗，从术前定位到疗效评价及追踪随访，均应用脑电地形图作为重要手段之一。认为脑电地形图作为检测手段可以较彻底切除病变组织，合理选择脑组织移植的方式，术后定期检查可以给临床疗效提供神经生理方面的客观指标和帮助判断远期疗效，因而脑电地形图在胎脑移植术治疗顽固性癫痫时，不论术前术后均应作为重要辅助手段。     

急性脑创伤脑组织介电特性

目的：研究家兔急性脑创伤脑组织介电特性（相对介电常数和电导率），为微波脑损伤检测技术提供依据。方法：实验组10只家兔以0.8 MPa压强撞击家兔颅顶部，建立急性脑创伤模型。在致伤部位开颅骨窗，采用开端同轴探针法在500 MHz～3 GHz频段范围内对致伤后30、45、60、75、90、105 min脑创伤部位脑组织进行介电特性测量。对照组10只家兔不撞击，其他步骤与实验组相同。结果：相同时间相同频率下，急性脑创伤脑组织的相对介电常数和电导率大于正常家兔脑组织（P<0.01）。在相同时间，急性脑创伤脑组织和正常家兔脑组织的相对介电常数随频率的增加而减小，电导率随频率的增加而增大。在相同频率，急性脑创伤脑组织相对介电常数和电导率随时间的增加而增大，而正常家兔脑组织的相对介电常数和电导率随时间的增加而保持相对稳定。结论：急性脑创伤后脑组织的介电特性发生明显改变，表明基于组织电特性的微波检测技术应用于脑创伤检测监测具有可行性。     

近红外无损伤脑血氧监测仪的研制——系统设计及实验验证

我们设计并研制了一种脑血氧监测仪,利用近红外光谱检测生物组织血、氧含量的原理,实现了对双侧脑组织局部血、氧参数的同时检测。检测探头采用两个不同波长的超高亮LED作为光源,通过两个光电传感器分别接收经左右大脑组织散射后的光信号,实现双探头检测双侧脑组织局部血、氧参数检测的功能。而且检测探头的外型结构经过特殊设计,有效地抑止了外界环境噪声同时减小了固定检测探头时给病人带来的不适感。仪器同时输出两侧脑组织的血容量和氧含量曲线,可以实现对病人的双侧脑组织血、氧变化参数进行长时间实时、连续的监测。最后利用生物模型实验验证了仪器的有效性。     

基于层间先验知识从脑MRI图像中自动提取脑组织

目的从脑MRI图像中提取脑组织,解决边缘模糊时脑和非脑组织难以分离的问题。方法首先利用各向异性扩散滤波的方法对脑MRI图像进行去噪处理;然后利用形态学的方法对初始脑MRI图像进行脑组织提取,在此分割结果的基础上,利用相邻层脑形态差异较小的特点,实现结构元素的自适应选取,完成从脑MRI图像中逐层准确、自动提取脑组织。结果采用不同来源的数据对算法性能进行了测试,结果优于经典背散射电子成像(BSE)方法的分割结果。结论利用层间先验知识有利于实现边缘模糊的脑组织自动准确提取,且适用性较强。     

Intracranial pressure and biochemical indicators of brain damage: follow-up study

Aim

To investigate the relation between metabolic parameters of the brain tissue, as direct indicators of real metabolic conditions within the brain, and intracranial pressure, as the consequence of pathophysiological changes.

Methods

Twelve patients with closed head injuries were followed up for 24 hours after injury. A Codman parenchymal intracranial pressure and a Neurotrend electrode were inserted within 3 hours after injury to monitor parenchymal intracranial pressure, brain tissue partial oxygen pressure (P_brO₂), brain tissue partial carbon dioxide pressure (P_brCO₂), pH, and brain tissue temperature. Data detected at 8-hourly intervals were compared with repeated measures analysis of variance.

Result

At the initial observation, the mean value of intracranial pressure was 22.2 ± 3.2 mm Hg. Although it increased at the second and decreased at the third measurement, the differences between the measurements were not significant (P = 0.320). The value of P_brCO₂ was increased from the beginning (63.3 ± 6.0 mm Hg), whereas P_brO₂ was within the normal range at the first measurement (38.9 ± 6.9 mm Hg), but significantly decreased after 8 hours (P = 0.004), remaining low at later time points.

Conclusion

After brain injury, changes in P_brCO₂ are visible earlier than those in P_brO₂. Improvement in intracranial pressure values did not necessary mean improvement in the brain tissue oxygenation. In addition to intracranial pressure, P_brO_2, P_brCO₂ and pH should also be monitored, as they directly reflect the real metabolic conditions within brain tissue and may be used in predictions about the outcome and possible therapeutic approaches.In head injuries, the brain is often threatened by various secondary pathophysiological processes leading to hypoxia or ischemia of the brain tissue (1). In the acute phase after head injury, the cerebral blood flow decreases, while the oxygen consumption in the brain tissue markedly increases (2-4). Secondary neurocytotoxic processes cause brain edema and increase the intracranial pressure, which further worsens cerebral metabolism, causing new neurocytotoxic complications. To prevent this vicious circle of pathophysiological processes, it is necessary to maintain adequate oxygenation of the brain tissue, which depends on the cerebral perfusion pressure and cerebral blood flow (5).Cerebral perfusion pressure equals the difference between the mean arterial pressure and intracranial pressure. Continuous measurement of the mean arterial pressure is always possible in intensive care units (ICU), and the treatment of head injuries today routinely includes monitoring of intracranial pressure. A cerebral perfusion pressure of about 70 mm Hg can optimally supply the brain with blood; if the brain tissue partial oxygen pressure is above 35 mm Hg, normal oxygenation of the brain tissue should be assured (5,6). Continuous assessment of brain oxygenation is possible with the use of commercial sensors.It is generally accepted that intracranial pressure is the key parameter in the assessment of patients with brain injuries. Moreover, patient treatment is based on the value of intracranial pressure (7). However, biochemical parameters in the brain tissue, such as the brain tissue partial oxygen pressure (P_brO₂), brain tissue partial carbon dioxide pressure (P_brCO₂), and pH, directly reflect the real metabolic conditions in the brain, whereas intracranial pressure is merely the consequence of pathophysiological changes.In the early phase after the injury, the value of intracranial pressure may still be within the normal range, while biochemical parameters are already pathologically changed. Therefore, these metabolic parameters should be monitored in the acute phase of brain injury. Our hypothesis was that the variations of intracranial pressure values and variations of biochemical parameters were not closely related, even in cases of closed brain injury. To test this, we measured intracranial pressure, brain tissue partial oxygen (P_brO₂) and carbon dioxide (P_brCO₂) pressure, pH, and temperature of the brain tissue at different time points within the first 24 hours after injury. We also investigated the relation between the changes of intracranial pressure values and variations of each of these metabolic parameters.     

高压氧干预脑梗死模型大鼠脑水肿及神经功能变化

背景：研究认为,高压氧有较好保护脑神经和脑细胞的作用,应用高压氧可使氧分压快速弥撒到相对缺氧的脑组织中,增加脑组织的血氧含量,促进脑水肿及脑神经功能的恢复。目的：观察大脑中动脉阻塞造模后高压氧干预对大鼠脑梗死组织水肿的影响,并探讨其对脑梗死大鼠神经功能保护的可能作用机制。方法：成年雌性SD大鼠65只,造模成功60只,随机区组法分为假手术组、脑梗死组、高压氧组,每组20 只,按照线栓线法建立大鼠大脑中动脉阻塞脑梗死模型。造模后3 d,通过TUNEL法检测各实验组大鼠脑梗死区神经细胞的凋亡情况。伤后72 h通过RT-PCR、Western blot检测脑梗死区周围AQP4/9、基质金属蛋白酶9/2基因转录和蛋白的表达,通过苏木精-伊红染色观察脑梗死区病理组织形态学变化,通过免疫组织化学法检测胶质纤维酸性蛋白的表达量,高压氧干预后24 h,3 d及伤后1、2 周行Longa行为学评分,检测神经功能的损伤情况。结果与结论：①高压氧组Longa行为学评分在治疗后1,2 d均较脑梗死组显著降低(P < 0.05)。②造模后3 d高压氧组细胞凋亡指数均明显低于脑梗死组(P < 0.05)。③造模后72 h,与脑梗死组相比高压氧组AQP4/9、基质金属蛋白酶9/2基因和蛋白表达均较显著降低(P < 0.05)。结果提示高压氧治疗通过减少大鼠脑梗死区神经细胞的凋亡和降低脑组织水肿,对脑梗死起到保护作用。中国组织工程研究杂志出版内容重点：肾移植;肝移植;移植;心脏移植;组织移植;皮肤移植;皮瓣移植;血管移植;器官移植;组织工程     

Continuous determination of the cerebrovascular changes induced by bicuculline and kainic acid in unanaesthetized spontaneously breathing rats

Cerebral blood flow was sequentially determined (every 2-3 min) with helium clearance in two "vulnerable" structures: the hippocampus and the frontoparietal cortex during bicuculline (n = 11) and kainic acid (n = 9)-induced seizures in unanaesthetized, spontaneously breathing rats. Tissue partial pressures of oxygen and carbon dioxide were continuously and simultaneously evaluated in the same brain areas. All these variables were measured by mass spectrometry with a single gas sampling cannula previously implanted in each structure. The systemic variables, arterial blood pressure, arterial partial pressures of oxygen and carbon dioxide, pH, and bicarbonate concentration were also determined. Arterial and venous catheters were chronically implanted several days prior to the definitive experiments. Bicuculline induced short (about 15 min), recurrent, generalized seizures, with an abrupt rise in arterial blood pressure, an arterial metabolic acidosis and comparable blood flow increases (4-fold) in the hippocampus and the neocortex. A marked increase in tissue partial pressure of oxygen was always preceded by an increase in tissue partial pressure of carbon dioxide. After the seizures, in the 5 rats that survived, cerebral blood flow was significantly lowered; tissue partial pressure of oxygen and partial pressure of carbon dioxide also decreased, but to a lesser extent. Histological examination revealed two types of lesions: predominantly selective chromatolysis but also ischaemic cell change. Kainic acid first induced a decrease in arterial pressure and then hypertension during status epilepticus, with a return of arterial pressure towards basal levels during the recovery period (4 h after the injection). Respiratory alkalosis occurred throughout the experiment. Cerebral blood flow increased progressively to become maximal during status epilepticus. This vasodilatation was greater in the hippocampus (x 8) than in the neocortex (x 4). During recovery, cerebral blood flow tended to decrease but remained significantly elevated. In both structures, tissue partial pressure of oxygen was first lowered while tissue partial pressure of carbon dioxide was elevated; with the occurrence of the wet dog shakes, tissue partial pressure of O2 increased and tissue partial pressure of CO2 decreased. The changes in tissue gases were maximal during status epilepticus and tended to return to their basal levels thereafter, but no decrease in tissue partial pressure of O2 was observed, even 4 h after kainic acid administration. Histological analysis demonstrated ischaemic cell changes, particularly in the limbic system.(ABSTRACT TRUNCATED AT 400 WORDS)     

脑血管多参数监测技术对脑血管病的实用价值研究

目的:探讨多参数脑血流监测技术在脑血管病诊断中的价值。方法:该项技术在92例脑血管患者和22例健康人中被应用了。结果:通过实时监测,观察了血压与血流量、血管弹性、血管外周阻力、血氧饱和度与其上述的关系。结论:脑血管多参数监测技术方法简便、经济、实用、可靠、无创,对脑血管病能达到早期诊断早期治疗的目的。     

Brain tissue oxygenation during transnasal endoscopic skull base procedures

PurposeWe aimed to study brain tissue oxygenation during the period of controlled reduction of arterial blood pressure – a maneuver often used in extended endoscopic skull base surgery for bloodless operative field.MethodsIntracranial pressure, arterial blood pressure and the resultant cerebral perfusion pressure were measured during extended endoscopic skull base surgery in 5 patients with diagnosed tumors of the skull base and arterial hypertension. Simultaneously, in those patients, we measured partial pressure of oxygen in the brain parenchyma (PbtO₂).ResultsValues of PbtO₂ lower than 15 mm Hg (risk of brain ischemia) were observed in 3 patients for periods of 40 min, 110 min and 123 min, respectively. In 2 of these patients, no hypotension (mean arterial pressure <65 mm Hg) was necessary for bloodless operative field. Another 2 patients had PbtO₂ above 30 mm Hg at the time when their mean arterial pressure was below 65 mm Hg. The time course of PbtO₂ followed that of cerebral perfusion pressure with a time lag of 40–60 s in all patients.ConclusionModerate reduction of arterial pressure, often used to obtain bloodless operative field during extended endoscopic skull base surgery, may in patients with the medical history of arterial hypertension be associated with critically low values of partial oxygen pressure in brain tissue.     

An automatic incubator oxygen monitor and control system

A system consisting of a temperature-compensated polarographic oxygen sensor, oxygen monitor, specially designed control adaptor, solenoid valve, and oxygen flow control valve was evaluated for its ability to monitor and control ambient oxygen concentration in an infant incubator. The response of the system to changes in environmental oxygen is linear, the life of the freshly charged sensor is satisfactory and the response time to changes in oxygen concentration (20–100 per cent) is 10 s. The system was successfully used with neonates requiring oxygen therapy. The ambient oxygen concentration was controlled to within ±1 per cent of the presselected level. High and low incubator oxygen flows had no effect on the skin, rectal, and ambient temperature, and there e was no accumulation of carbon dioxide. While monitoring the neonate's tissue oxygen, this system permits controlled ‘step down aclimatization’ from high to normal environmental oxygen concentrations thereby minimizing the untoward effects of hypoxaemia and hyperoxaemia often seen with current manual methods.     

Monitoring the injured brain in the intensive care unit

The primary aim of managing patients with acute brain injury in the intensive care unit is to minimise secondary injury by maintaining cerebral perfusion and oxygenation. The mechanisms of secondary injury are frequently triggered by secondary insults, which may be subtle and remain undetected by the usual systemic physiological monitoring. Continuous monitoring of the central nervous system in the intensive care unit can serve two functions. Firstly it will help early detection of these secondary cerebral insults so that appropriate interventions can be instituted. Secondly, it can help to monitor therapeutic interventions and provide online feedback. This review focuses on the monitoring of intracranial pressure, blood flow to the brain (Transcranial Doppler), cerebral oxygenation using the methods of jugular bulb oximetry, near infrared spectroscopy and implantable sensors, and the monitoring of function using electrophysiological techniques.     

Controlled respiratory gas delivery to embryonic renal epithelial explants in perfusion culture

During generation of artificial tissues high levels of oxygen are usually available whereas after implantation into a recipient's body the implant is not vascularized immediately, which leads to low oxygen partial pressures within the implanted tissue. Under these conditions cells will experience an oxygen shortage, contrasting with the abundance of oxygen during culture. It is uncertain whether tissues can be trained to tolerate such an acute hypoxic situation so that nonphysiological stress reactions and tissue necrosis can be avoided. To investigate the effects of varying oxygen levels on embryonic renal tissue in vitro we have been developing a model system combining continuous medium renewal with the ability to control levels of oxygen and carbon dioxide by gas equilibration through gas-permeable tubing. Renal embryonic tissue from neonatal rabbit was cultured in serum-free Iscove's modified Dulbecco's medium at 45, 90, 115, and 160 mmHg oxygen partial pressure for 14 days under continuous medium exchange in such a setup. After a 14-day culture period tissue sections were analyzed by cell biological methods and compared with fresh tissue histology. Surprisingly, embryonic renal explants survive and maintain good morphology for 14 days under all O(2) conditions tested. Expression of cytokeratin 19 within the established epithelium remains unchanged, indicating a structurally intact tissue. However, Na/K-ATPase is clearly downregulated under low O(2) conditions, whereas COX-2 expression increases drastically. An antiparallel effect of decreased O(2) concentrations on glycoprotein expression can be demonstrated with the lectin Dolichos biflorus agglutinin. Scanning electron microscopy reveals oxygen-dependent changes in cellular surface differentiation of developed collecting duct epithelium.     

Mean cerebral blood flow measurements using phase contrast MRI in the first year of life

Alterations in cerebral blood flow (CBF) are believed to be linked to many of the neurological pathologies that affect neonates and small infants. CBF measurements are nonetheless often difficult to perform in this population, as many techniques rely on radioactive tracers or other invasive methods. In this study, mean global CBF was measured in 21 infants under the age of one, using non-invasive MRI techniques adapted to the neonatal population. Mean CBF was computed as the ratio of blood flow delivered to the brain (measured using phase contrast MRI) and brain volume (computed by segmenting anatomical MR images). Tests in adult volunteers and repeated measurements showed the flow measurements using the proposed method to be both accurate and reproducible. It was also found that cardiac gating need not be employed in infants with no known cardiac pathology. The developed technique can easily be appended to a neonatal MRI examination to provide rapid, robust, and non-invasive estimates of mean CBF, thus providing a means to monitor developmental or pathology-related alterations in cerebral perfusion and the impact of different treatment courses. In the imaged cohort, mean CBF and flow to the brain were found to rapidly increase during the first year of life (from approx. 25 to 60 ml blood/100 ml tissue/min), in good agreement with literature from other modalities where available. Mean CBF also showed a significant correlation with arterial oxygen saturation level and heart rate, but no significant correlation was found between CBF and the hematocrit or body temperature.