Noninvasive Monitoring of Cerebral Blood Flow Autoregulation

Study Overview
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Brief Summary
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Rheoencephalography (REG) shows promise as a method for noninvasive neuromonitoring, because it reflects cerebrovascular reactivity. This protocol will study clinical and technical conditions required to use REG. Additionally, our goal is to study noninvasive peripheral bioimpedance pulse waveforms in order to substitute invasive SAP. A previous study demonstrated that REG can be used to detect spreading depolarization (SD), the early sign of brain metabolic disturbance. SD can be measured invasively with DC EEG amplifiers only. Our goal is to create an automatic notification function for REG monitoring indicating change of clinical conditions.

Detailed Description
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Neuromonitoring of patients with severe neurological illness are detailed elsewhere. In the setting of cerebral edema, ICP monitoring is a staple of neurocritical care. Pressure AR is an important hemodynamic mechanism that protects the brain against inappropriate fluctuations in CBF in the face of changing CPP. Both static and dynamic AR have been monitored in neurocritical care to aid prognostication and contribute to individualizing optimal CPP targets in patients. Theoretically, failure of cerebral AR is associated with poor outcomes in various acute neurological diseases. Continuous bedside monitoring of autoregulation is now feasible and should be considered as a part of multimodality monitoring including measurement of pressure reactivity. A previous study documented that REG (REGx) and ICP (PRx) has high correlation in order to detect the lower limit of CBF AR. The fundamental relationships between SAP, vessel tone, cerebral blood volume and ICP form the basis for the pressure reactivity index (PRx). PRx is analogous to other time domain AR indices and is calculated as the continuous correlation between thirty consecutive time-averaged (10 s) SAP and ICP values. A positive index (positive correlation) implies impaired passive CBF AR, while a negative index (inverse correlation) implies intact, active AR. The utility and feasibility of REG as a monitoring modality is previously demonstrated and validated as a reflection of cerebrovascular reactivity. The bioimpedance amplifier was used previously at Walter Reed Army Institute of Research (WRAIR) and Naval Medical Research Center (Silver Spring, MD); and has an FDA safety clearance. It is expected that REG can predict evolving vasospasm and expanding intracranial bleeding amongst several other clinical applications.

Official Title
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Noninvasive Monitoring of Cerebral Blood Flow Autoregulation

Conditions
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Cerebral Edema, Intracranial Pressure Increase

Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Intact fronto-temporal area Intact lower arm area Clinical suspicion of elevated intracranial pressure Exclusion Criteria: N/A

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Cerebral Blood Flow Autoregulation (CBF AR) | Cerebral Blood Flow Autoregulation (CBF AR) will be analyzed based on noninvasive recordings (bioimpedance) by using a dedicated software for this purpose (part of ICM+ program, incorporated into a WRAIR-made software (DataLyser)). In this case CBF AR is called REGx. | through hospital admission, an average of 10 days | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| ICP Elevation | Morphological analysis of REG pulse waveform in order to detect ICP elevation, and establish the correlation between REGx and REG pulse waveform morphology. | through hospital admission, an average of 10 days | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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neuromonitoring, intracranial pressure (ICP), cerebral blood flow autoregulation, Rheoencephalography (REG), noninvasive neuromonitoring, cerebral edema, autoregulation, Cerebral Perfusion Pressure, Pressure reactivity index