近红外光谱成像在脑血管病诊疗中的应用价值

对脑血管病患者的脑组织氧合情况实施床旁监测,对脑血管病的诊治及预后改善有重要价值。近红外光谱成像（near infrared spectroscopy,NIRS）作为一项新兴的脑成像技术,具有价格低廉、操作便捷、非侵入性等优点,逐渐成为脑血管病研究的焦点。本文介绍了NIRS的基本原理,探讨了NIRS在急性脑梗死早期识别、梗死后再灌注疗效评估、大面积脑梗死继发恶性脑水肿预测等方面的应用价值,预测了NIRS在大脑近皮层出血病情监测中的应用前景。此外,在蛛网膜下腔出血诊疗领域,NIRS通过动态监测脑氧饱和度,在迟发性脑缺血监测及术后功能结局预测等方面也有着较大的应用潜力。最后,本文基于NIRS的优势和不足,展望了未来适合NIRS应用的临床场景。加强NIRS在脑血管病领域的研究,将使实时评估脑血管病院前、院内的精准动态成为可能。     

Monitoring anesthesia using simultaneous functional Near Infrared Spectroscopy and Electroencephalography

ObjectiveThis study aims to understand the neural and hemodynamic responses during general anesthesia in order to develop a comprehensive multimodal anesthesia depth monitor using simultaneous functional Near Infrared Spectroscopy (fNIRS) and Electroencephalogram (EEG).Methods37 adults and 17 children were monitored with simultaneous fNIRS and EEG, during the complete general anesthesia process. The coupling of fNIRS signals with neuronal signals (EEG) was calculated. Measures of complexity (sample entropy) and phase difference were also quantified from fNIRS signals to identify unique fNIRS based biomarkers of general anesthesia.ResultsA significant decrease in the complexity and power of fNIRS signals characterize the anesthesia maintenance phase. Furthermore, responses to anesthesia vary between adults and children in terms of neurovascular coupling and frontal EEG alpha power.ConclusionsThis study shows that fNIRS signals could reliably quantify the underlying neuronal activity under general anesthesia and clearly distinguish the different phases throughout the procedure in adults and children (with less accuracy).SignificanceA multimodal approach incorporating the specific differences between age groups, provides a reliable measure of anesthesia depth.     

Monitoring of Cerebrovascular Autoregulation: Facts, Myths, and Missing Links

The methods for continuous assessment of cerebral autoregulation using correlation, phase shift, or transmission (either in time- or frequency-domain) were introduced a decade ago. They express dynamic relationships between slow waves of transcranial Doppler (TCD), blood flow velocity (FV) and cerebral perfusion pressure (CPP), or arterial pressure (ABP). We review a methodology and clinical application of indices useful for monitoring cerebral autoregulation and pressure-reactivity in various scenarios of neuro-critical care. Facts: Poor autoregulation and loss of pressure-reactivity are independent predictors of fatal outcome following head injury. Autoregulation is impaired by too low or too high CPP when compared to autoregulation with normal CPP (usually between 60 and 85 mmHg; and these limits are highly individual). Hemispheric asymmetry of the bi-laterally assessed autoregulation has been associated with asymmetry of CT scan findings: autoregulation was found to be worse ipsilateral to contusion or lateralized edema causing midline shift. The pressure-reactivity (PRx index) correlated with a state of low CBF and CMRO₂ revealed using PET studies. The PRx is easier to monitor over prolonged periods of time than the TCD-based indices as it does not require fixation of external probes. Continuous monitoring with the PRx can be used to direct CPP-oriented therapy by determining the optimal CPP for pressure-reactivity. Autoregulation indices are able to reflect transient changes of autoregulation, as seen during plateau waves of ICP. However, minute-to-minute assessment of autoregulation has a poor signal-to-noise ratio. Averaging across time (30 min) or by combining with other relevant parameters improves the accuracy. Myths: It is debatable whether the TCD-based indices in head injured patients can be calculated using ABP instead of CPP. Thresholds for functional and disturbed autoregulation dramatically depends on arterial tension of CO₂—therefore, comparison between patients cannot be performed without comparing their PaCO₂. The TCD pulsatility index cannot accurately detect the lower limit of autoregulation. Missing Links: We still do not know whether autoregulation-oriented therapy can be understood as a consensus between CPP-directed protocols and the Lund-concept. What are the links between endothelial function and autoregulation indices? Can autoregulation after head injury be improved with statins or EPO, as in subarachnoid hemorrhage? In conclusion, monitoring cerebral autoregulation can be used in a variety of clinical scenarios and may be helpful in delineating optimal therapeutic strategies.     

Different Indices to Assess Cerebrovascular Autoregulation Have Different Dynamic Properties

Neurocritical Care -     

Validation of Near-Infrared Spectroscopy for Monitoring Cerebral Autoregulation in Comatose Patients

Background

The diagnosis of nosocomial bacterial ventriculitis in patients with subarachnoid hemorrhage (SAH) can be challenging.

Methods

We performed a retrospective study on the diagnostic accuracy of clinical and laboratory characteristics for the diagnosis of bacterial ventriculitis in 209 consecutive patients with an aneurysmal SAH admitted in a tertiary referral center from 2008 to 2010. Diagnostic value of clinical characteristics and inflammatory indexes in CSF and blood were determined for three diagnostic categories: (1) no suspicion for bacterial ventriculitis; (2) clinical suspicion for bacterial ventriculitis, defined as initiation of empirical antibiotic treatment for ventriculitis, but negative CSF cultures; and (3) CSF culture-positive bacterial ventriculitis.

Results

Empirical antibiotics for suspected ventriculitis was initiated in 48 of 209 (23 %) patients. CSF cultures were positive in 11 (5 %) patients. Within the group of suspected ventriculitis, only longer duration of CSF drainage and lower CSF red blood cell counts predicted for culture positivity. None of the other clinical features or inflammatory indexes in CSF and blood were associated with culture-proven bacterial ventriculitis.

Conclusions

Nosocomial bacterial ventriculitis in patients with aneurysmal SAH is often suspected but confirmed by culture in a minority of cases. Improvement of diagnostics for nosocomial bacterial ventriculitis in patients with aneurysmal SAH is needed.

     

Comparison of Non-invasive and Invasive Arterial Blood Pressure Measurement for Assessment of Dynamic Cerebral Autoregulation

Background

There is a growing interest in measuring cerebral autoregulation in patients with acute brain injury. Non-invasive finger photo-plethysmography (Finapres) is the method of choice to relate arterial blood pressure to changes in cerebral blood flow. Among acutely ill patients, however, peripheral vasoconstriction often limits the use of Finapres requiring direct intravascular blood pressure measurement. We evaluated how these two different forms of blood pressure monitoring affect the parameters of dynamic cerebral autoregulation (DCA).

Methods

We performed 37 simultaneous recordings of BP and cerebral blood flow velocity in 15 patients with acute brain injury. DCA was estimated in the frequency domain using transfer function analysis to calculate phase shift, gain, and coherence. In addition the mean velocity index (Mx) was calculated for assessment of DCA in the time domain.

Results

The mean patient age was 58.1 ± 15.9 years, 80 % (n = 12) were women. We found good inter-method agreement between Finapres and direct intravascular measurement using Bland–Altman and correlation analyses. Finapres gives higher values for the efficiency of dynamic CA compared with values derived from radial artery catheter, as indicated by biases in the phase (26.3 ± 11.6° vs. 21.7 ± 10.5°, p = 0.001) and Mx (0.571 ± 0.137 vs. 0.649 ± 0.128, p < 0.001). Gain in the low frequency range did not significantly differ between the two arterial blood pressure methods. The average coherence between CBFV and ABP was higher when BP was measured with arterial catheter for frequencies above 0.05 Hz (0.8 vs. 0.73, p < 0.001).

Conclusion

Overall, both methods yield similar results and can be used for the assessment of DCA. However, there was a small but significant difference for both mean Mx and phase shift, which would need to be adjusted for during monitoring of patients when using both methods. When available, invasive arterial blood pressure monitoring may improve accuracy and thus should be the preferred method for DCA assessment in the ICU.     

Monitoring of Cerebral Autoregulation

Pressure autoregulation is an important hemodynamic mechanism that protects the brain against inappropriate fluctuations in cerebral blood flow in the face of changing cerebral perfusion pressure (CPP). Static autoregulation represents how far cerebrovascular resistance changes when CPP varies, and dynamic autoregulation represents how fast these changes happen. Both have been monitored in the setting of neurocritical care to aid prognostication and contribute to individualizing CPP targets in patients. Failure of autoregulation is associated with a worse outcome in various acute neurological diseases. Several studies have used transcranial Doppler ultrasound, intracranial pressure (ICP with vascular reactivity as surrogate measure of autoregulation), and near-infrared spectroscopy to continuously monitor the impact of spontaneous fluctuations in CPP on cerebrovascular physiology and to calculate derived variables of autoregulatory efficiency. Many patients who undergo such monitoring demonstrate a range of CPP in which autoregulatory efficiency is optimal. Management of patients at or near this optimal level of CPP is associated with better outcomes in traumatic brain injury. Many of these studies have utilized the concept of the pressure reactivity index, a correlation coefficient between ICP and mean arterial pressure. While further studies are needed, these data suggest that monitoring of autoregulation could aid prognostication and may help identify optimal CPP levels in individual patients.     

Continuous Monitoring of Cerebrovascular Reactivity Using Pulse Waveform of Intracranial Pressure

Background

Guidelines for the management of traumatic brain injury (TBI) call for the development of accurate methods for assessment of the relationship between cerebral perfusion pressure (CPP) and cerebral autoregulation and to determine the influence of quantitative indices of pressure autoregulation on outcome. We investigated the relationship between slow fluctuations of arterial blood pressure (ABP) and intracranial pressure (ICP) pulse amplitude (an index called PAx) using a moving correlation technique to reflect the state of cerebral vasoreactivity and compared it to the index of pressure reactivity (PRx) as a moving correlation coefficient between averaged values of ABP and ICP.

Methods

A retrospective analysis of prospective 327 TBI patients (admitted on neurocritical care unit of a university hospital in the period 2003?C2009) with continuous ABP and ICP monitoring.

Results

PAx was worse in patients who died compared to those who survived (?0.04?±?0.15 vs. ?0.16?±?0.15, ??²?=?28, p?2?=?6, p?=?0.01).

Conclusions

PAx is a new modified index of cerebrovascular reactivity which performs equally well as established PRx in long-term monitoring in severe TBI patients, but importantly is potentially more robust at lower values of ICP. In view of establishing an autoregulation-oriented CPP therapy, continuous determination of PAx is feasible but its value has to be evaluated in a prospective controlled trail.     

卵圆孔未闭介入封堵术前后脑血流自动调节监测一例报道

<正>1病例介绍女性患者,49岁,因"间断头痛20余年,加重1个月余,左侧肢体活动不灵1 d"于2014年4月9日就诊我院门诊。长期慢性头痛病史,情绪变化、生活习惯改变易诱发,休息或自服"去痛片"后可缓解,否认头痛先兆症状。上述症状反复发作,近1个月余加重,表现为头痛频率增加,持续时间延长。1 d前于看电视起身时发现左侧肢体活动不灵,上肢持物不稳,手指精细活     

传递函数分析动态脑血流自动调节：源于国际脑血流自动调节研究网络的白皮书

脑血流自动调节（cerebral autoregulation,CA）是血压变化时大脑维持足够脑灌注的内在能力。过去的30年,研究者已经提出了诸多分析CA的方法,但至今无公认的金标准,采用什么方法定量CA仍是个人主观的选择。尽管如此,由于CA的概念代表了血压（刺激或者输入信号）与脑血流（反应或者输出信号）之间的动态关系,故目前最通用的研究血压自发波动的分析方法是传递函数分析。虽然理论上可行,但是文献显示,传递函数分析方法在实践中存在相当大的主观性,这限制了研究之间的比较,也阻碍了其临床应用。因此,本白皮书旨在规范化研究动态CA的传递函数分析方法的参数及设置,建立标准,以利于其临床应用,该推荐的研发始于（但不限于）脑血流自动调节研究网络（CARNet-www.car-net.org）。     

One-Minute Dynamic Cerebral Autoregulation in Severe Head Injury Patients and its Comparison with Static Autoregulation. A Transcranial Doppler Study

Objective  To compare dynamic and static responses of cerebral blood flow to sudden or slow changes in arterial pressure in severe traumatic brain injury (TBI) patients. Design  Prospective study. Patients and Methods  We studied 12 severe TBI patients, age 16–63 years, and median GCS 6. We determined the dynamic cerebral autoregulation: response of cerebral blood flow velocity to a step blood pressure drop, and the static cerebral autoregulation: change in cerebral blood flow velocity after a slow hypertensive challenge. Results  During the dynamic response, the median drop in arterial pressure was 21 mm Hg. Dynamic response was graded between 9 (best) and 0 (worst). The median value was 5; four patients showed high values, (8–9), five patients showed intermediate values (4–6). In three patients (value = 0), the CBFV drop was greater than the cerebral perfusion pressure drop, and maintained through 60 s. The static cerebral autoregulation was preserved in 6/11 patients. The comparison between the two showed four different combinations. The five patients with impaired static cerebral autoregulation showed unfavorable outcome. Conclusions  A sharp dynamic vasodilator response could not be sustained, and a slow or absent reaction to a sudden hypotensive challenge could show an acceptable cerebral autoregulation in the steady state. We found that patients with impaired static cerebral autoregulation had a poor outcome, whereas those with preserved static cerebral autoregulation experience favorable outcomes.     

床旁经颅多普勒在重症脑血管病监护中的应用

经颅多普勒（transcranial doppler,TCD）的2MHz超声探头可以透过颅骨薄弱部位实时动态监
测颅底Willis环组成的血管血流速度,从而得到脑血流动力学等参数,在重症脑血管病领域得到了广
泛的应用。TCD一直是蛛网膜下腔出血床旁诊断的有力武器,但是TCD诊断的血管痉挛对临床预后的
判断受到临床挑战。血管再通迎来春天,床旁TCD可以对血管再通治疗后高灌注综合征的发生起到
预警作用,而且可以随访检测血管再通的治疗效果。TCD对于无创颅内压监测的指示作用有待国际公
认的可重复的数学模型出现。     

脑血管疾病血管内治疗的麻醉管理与监测

目的 探讨脑血管疾病微导管血管内介入治疗的麻醉管理与监测。方法 22例脑血管疾病患者手术开始前先用咪唑安定0.06mg/kg缓慢滴入,静注异丙酚1mg/kg镇静,随后接静脉输注泵,以25～75μg/kg/min持续输注,同时以1～3μg/kg/min持续输入硝普钠控制性降压。结果 22例患者均安全度过手术。栓塞时血压明显较术前低,术中心率、血氧饱和度较术前无明显变化。适度镇静百分比为86％(19/22),完全遗忘百分比73％(16/22)。3例病人出现术后恶心呕吐。结论 有监测的麻醉管理用于脑血管疾病微导管血管内介入治疗安全有效。     

Real-time Noninvasive Monitoring of Intracranial Fluid Shifts During Dialysis Using Volumetric Integral Phase-Shift Spectroscopy (VIPS): A Proof-of-Concept Study

Background

Cerebral edema, which is associated with increased intracranial fluid, is often a complication of many acute neurological conditions. There is currently no accepted method for real-time monitoring of intracranial fluid volume at the bedside. We evaluated a novel noninvasive technique called “Volumetric Integral Phase-shift Spectroscopy (VIPS)” for detecting intracranial fluid shifts during hemodialysis.

Methods

Subjects receiving scheduled hemodialysis for end-stage renal disease and without a history of major neurological conditions were enrolled. VIPS monitoring was performed during hemodialysis. Serum osmolarity, electrolytes, and cognitive function with mini-mental state examination (MMSE) were assessed.

Results

Twenty-one monitoring sessions from 14 subjects (4 women), mean group age 50 (SD 12.6), were analyzed. The serum osmolarity decreased by a mean of 6.4 mOsm/L (SD 6.6) from pre- to post-dialysis and correlated with an increase in the VIPS edema index (E-Dex) of 9.7% (SD 12.9) (Pearson’s correlation r = 0.46, p = 0.037). Of the individual determinants of serum osmolarity, changes in serum sodium level correlated best with the VIPS edema index (Pearson’s correlation, r = 0.46, p = 0.034). MMSE scores did not change from pre- to post-dialysis.

Conclusions

We detected an increase in the VIPS edema index during hemodialysis that correlated with decreased serum osmolarity, mainly reflected by changes in serum sodium suggesting shifts in intracranial fluids.