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cerebral vascular autoregulation

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https://www.readbyqxmd.com/read/29773488/identifying-the-myogenic-and-metabolic-components-of-cerebral-autoregulation
#1
S J Payne
Cerebral autoregulation is the term used to describe a number of mechanisms that act together to maintain a near constant cerebral blood flow in response to changes in arterial blood pressure. These mechanisms are complex and known to be affected in a range of cerebrovascular diseases. However, it can be difficult to assign an alteration in cerebral autoregulation to one of the underlying physiological mechanisms without the use of a complex mathematical model. In this paper, we thus set out a new approach that enables these mechanisms to be related to the autoregulation behaviour and hence inferred from experimental measurements...
May 14, 2018: Medical Engineering & Physics
https://www.readbyqxmd.com/read/29726017/effect-of-cerebral-flow-autoregulation-function-on-cerebral-flow-rate-under-continuous-flow-left-ventricular-assist-device-support
#2
Selim Bozkurt
Neurological complications in continuous flow left ventricular assist device (CF-LVAD) patients are the second-leading risk of death after multi-organ failure. They are associated with altered blood flow in the cardiovascular system because of CF-LVAD support. Moreover, an impaired cerebral autoregulation function may also contribute to complications such as hyperperfusion in the cerebral circulation under mechanical circulatory support. The aim of this study is to evaluate the effect of cerebral autoregulatory function on cerebral blood flow rate under CF-LVAD support...
May 3, 2018: Artificial Organs
https://www.readbyqxmd.com/read/29677060/cerebral-small-vessel-but-not-large-vessel-disease-is-associated-with-impaired-cerebral-autoregulation-during-cardiopulmonary-bypass-a-retrospective-cohort-study
#3
Yohei Nomura, Roland Faegle, Daijiro Hori, Abbas Al-Qamari, Alexander J Nemeth, Rebecca Gottesman, Gayane Yenokyan, Charles Brown, Charles W Hogue
BACKGROUND: Impaired cerebral blood flow (CBF) autoregulation during cardiopulmonary bypass (CPB) is associated with stroke and other adverse outcomes. Large and small arterial stenosis is prevalent in patients undergoing cardiac surgery. We hypothesize that large and/or small vessel cerebral arterial disease is associated with impaired cerebral autoregulation during CPB. METHODS: A retrospective cohort analysis of data from 346 patients undergoing cardiac surgery with CPB enrolled in an ongoing prospectively randomized clinical trial of autoregulation monitoring were evaluated...
April 17, 2018: Anesthesia and Analgesia
https://www.readbyqxmd.com/read/29567858/serum-bicarbonate-concentration-and-cognitive-function-in-hypertensive-adults
#4
Mirela Dobre, Sarah A Gaussoin, Jeffrey T Bates, Michel B Chonchol, Debbie L Cohen, Thomas H Hostetter, Kalani L Raphael, Addison A Taylor, Alan J Lerner, Jackson T Wright, Mahboob Rahman
BACKGROUND AND OBJECTIVES: Cognitive function worsens as kidney function declines, but mechanisms contributing to this association are not completely understood. Metabolic acidosis, a common complication of CKD, leads to neural networks overexcitation and is involved in cerebral autoregulation. We aimed to evaluate the association between serum bicarbonate concentration as a measure of metabolic acidosis, and cognitive function in hypertensive adults with and without CKD. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: Five cognitive summary scores were measured (global cognitive function, executive function, memory, attention/concentration, and language) in 2853 participants in the Systolic BP Intervention Trial (SPRINT)...
March 22, 2018: Clinical Journal of the American Society of Nephrology: CJASN
https://www.readbyqxmd.com/read/29499637/chronic-kidney-disease-and-poor-outcomes-in-ischemic-stroke-is-impaired-cerebral-autoregulation-the-missing-link
#5
Pedro Castro, Elsa Azevedo, Isabel Rocha, Farzaneh Sorond, Jorge M Serrador
BACKGROUND: Chronic kidney disease increases stroke incidence and severity but the mechanisms behind this cerebro-renal interaction are mostly unexplored. Since both vascular beds share similar features, microvascular dysfunction could be the possible missing link. Therefore, we examined the relationship between renal function and cerebral autoregulation in the early hours post ischemia and its impact on outcome. METHODS: We enrolled 46 ischemic strokes (middle cerebral artery)...
March 2, 2018: BMC Neurology
https://www.readbyqxmd.com/read/29492574/autoregulating-cerebral-tissue-selfishly-exploits-collateral-flow-routes-through-the-circle-of-willis
#6
Flora A Kennedy McConnell, Stephen J Payne
OBJECTIVE: Ischemic stroke is a leading cause of death and disability. Autoregulation and collateral blood flow through the circle of Willis both play a role in preventing tissue infarction. A steady-state model of the cerebral arterial network was used to investigate the interaction of these mechanisms when autoregulation is impaired ipsilateral to an occluded artery. MATERIALS AND METHODS: Twelve structural variants of the circle of Willis were modelled with left internal carotid artery occlusion and coupled with (1) a passive model of the cerebral vascular bed, (2) a steady-state model of an autoregulating cerebral vascular bed, and (3) a model in which the contralateral hemisphere autoregulates and the ipsilateral hemisphere does not...
2018: Acta Neurochirurgica. Supplement
https://www.readbyqxmd.com/read/29454381/human-cerebrovascular-function-in-health-and-disease-insights-from-integrative-approaches
#7
REVIEW
Erin D Ozturk, Can Ozan Tan
BACKGROUND: The marked increase in the size of the brain, and consequently, in neural processing capability, throughout human evolution is the basis of the higher cognitive function in humans. However, greater neural, and thus information processing capability, comes at a significant metabolic cost; despite its relatively small size, the modern human brain consumes almost a quarter of the glucose and oxygen supply in the human body. Fortunately, several vascular mechanisms ensure sufficient delivery of glucose and oxygen to the active neural tissue (neurovascular coupling), prompt removal of neural metabolic by-products (cerebral vasoreactivity), and constant global blood supply despite daily variations in perfusion pressure (cerebral autoregulation)...
February 17, 2018: Journal of Physiological Anthropology
https://www.readbyqxmd.com/read/29437601/relationship-between-the-ambulatory-arterial-stiffness-index-and-the-lower-limit-of-cerebral-autoregulation-during-cardiac-surgery
#8
Yurie Obata, Viachaslau Barodka, Dan E Berkowitz, Allan Gottschalk, Charles W Hogue, Jochen Steppan
BACKGROUND: Pulse pressure, the ambulatory arterial stiffness index (AASI), and the symmetric AASI are established predictors of adverse cardiovascular outcomes. However, little is known about their relationship to cerebral autoregulation. This study evaluated whether these markers of vascular properties relate to the lower limit of cerebral autoregulation (LLA). METHODS AND RESULTS: The LLA was determined during cardiac surgery with transcranial Doppler ultrasonography in 181 patients...
February 8, 2018: Journal of the American Heart Association
https://www.readbyqxmd.com/read/29379105/developmental-maturation-and-alpha-1-adrenergic-receptors-mediated-gene-expression-changes-in-ovine-middle-cerebral-arteries
#9
Dipali Goyal, Ravi Goyal
The Alpha Adrenergic Signaling Pathway is one of the chief regulators of cerebrovascular tone and cerebral blood flow (CBF), mediating its effects in the arteries through alpha1-adrenergic receptors (Alpha1AR). In the ovine middle cerebral artery (MCA), with development from a fetus to an adult, others and we have shown that Alpha1AR play a key role in contractile responses, vascular development, remodeling, and angiogenesis. Importantly, Alpha1AR play a significant role in CBF autoregulation, which is incompletely developed in a premature fetus as compared to a near-term fetus...
January 29, 2018: Scientific Reports
https://www.readbyqxmd.com/read/29319396/detrimental-effect-of-systemic-vascular-risk-factors-on-brain-hemodynamic-function-assessed-with-mri
#10
Kevin S King, Min Sheng, Peiying Liu, Christopher D Maroules, Craig D Rubin, Ron M Peshock, Roderick W McColl, Hanzhang Lu
Background and purpose Vascular risk factors have been associated with decreased cerebral blood flow (CBF) but this is etiologically nonspecific and may result from vascular insufficiency or a response to decreased brain metabolic activity. We apply new MRI techniques to measure oxygen extraction fraction (OEF) and cerebral metabolic rate of oxygen consumption (CMRO2 ), hypothesizing that decreased CBF related to these vascular risk factors will be associated with increased OEF, confirming a primary vascular insufficiency...
January 1, 2018: Neuroradiology Journal
https://www.readbyqxmd.com/read/29311754/correlation-between-cerebral-hemodynamic-and-perfusion-pressure-changes-in-non-human-primates
#11
A Ruesch, M A Smith, G Wollstein, I A Sigal, S Nelson, J M Kainerstorfer
The mechanism that maintains a stable blood flow in the brain despite changes in cerebral perfusion pressure (CPP), and therefore guaranties a constant supply of oxygen and nutrients to the neurons, is known as cerebral autoregulation (CA). In a certain range of CPP, blood flow is mediated by a vasomotor adjustment in vascular resistance through dilation of blood vessels. CA is known to be impaired in diseases like traumatic brain injury, Parkinson's disease, stroke, hydrocephalus and others. If CA is impaired, blood flow and pressure changes are coupled and the oxygen supply might be unstable...
February 2017: Proceedings of SPIE
https://www.readbyqxmd.com/read/29179622/traumatic-brain-injury-impairs-myogenic-constriction-of-cerebral-arteries-role-of-mitochondria-derived-h-2-o-2-and-trpv4-dependent-activation-of-bk-ca-channels
#12
Nikolett Szarka, Mallikarjuna R Pabbidi, Krisztina Amrein, Endre Czeiter, Gergely Berta, Krisztina Pohoczky, Zsuzsanna Helyes, Zoltan Ungvari, Akos Koller, Andras Buki, Peter Toth
Traumatic brain injury (TBI) impairs autoregulation of cerebral blood flow, which contributes to the development of secondary brain injury, increasing mortality of patients. Impairment of pressure-induced myogenic constriction of cerebral arteries plays a critical role in autoregulatory dysfunction; however, the underlying cellular and molecular mechanisms are not well understood. To determine the role of mitochondria-derived H2 O2 and large-conductance calcium-activated potassium channels (BKCa ) in myogenic autoregulatory dysfunction, middle cerebral arteries (MCAs) were isolated from rats with severe weight drop-impact acceleration brain injury...
January 12, 2018: Journal of Neurotrauma
https://www.readbyqxmd.com/read/29104807/neural-vascular-mechanism-for-the-cerebral-blood-flow-autoregulation-after-hemorrhagic-stroke
#13
REVIEW
Ming Xiao, Qiang Li, Hua Feng, Le Zhang, Yujie Chen
During the initial stages of hemorrhagic stroke, including intracerebral hemorrhage and subarachnoid hemorrhage, the reflex mechanisms are activated to protect cerebral perfusion, but secondary dysfunction of cerebral flow autoregulation will eventually reduce global cerebral blood flow and the delivery of metabolic substrates, leading to generalized cerebral ischemia, hypoxia, and ultimately, neuronal cell death. Cerebral blood flow is controlled by various regulatory mechanisms, including prevailing arterial pressure, intracranial pressure, arterial blood gases, neural activity, and metabolic demand...
2017: Neural Plasticity
https://www.readbyqxmd.com/read/29043544/icp-versus-laser-doppler-cerebrovascular-reactivity-indices-to-assess-brain-autoregulatory-capacity
#14
F A Zeiler, J Donnelly, D Cardim, D K Menon, P Smielewski, M Czosnyka
BACKGROUND: To explore the relationship between various autoregulatory indices in order to determine which approximate small vessel/microvascular (MV) autoregulatory capacity most accurately. METHODS: Utilizing a retrospective cohort of traumatic brain injury patients (N = 41) with: transcranial Doppler (TCD), intracranial pressure (ICP) and cortical laser Doppler flowmetry (LDF), we calculated various continuous indices of autoregulation and cerebrovascular responsiveness: A...
October 17, 2017: Neurocritical Care
https://www.readbyqxmd.com/read/28991702/cerebral-autoregulation-is-preserved-in-multiple-sclerosis-patients
#15
Daniel Ferreira, Pedro Castro, Gonçalo Videira, João Pedro Filipe, Rosa Santos, Maria José Sá, Elsa Azevedo, Pedro Abreu
Multiple sclerosis (MS) is an inflammatory disease that may also be associated with vascular dysfunction. One master component of vascular regulation is cerebral autoregulation (CA). We aimed to investigate the integrity of CA in MS patients and study its relationship with autonomic dysfunction (AD), magnetic-resonance-imaging (MRI) lesion load and hemodynamic parameters. We enrolled 20 relapsing-remitting MS and 20 healthy subjects. CA was assessed by transfer function analysis parameters (coherence, gain and phase), as obtained in the very low, low and high-frequency domains (VLF, LF, HF, respectively)...
October 15, 2017: Journal of the Neurological Sciences
https://www.readbyqxmd.com/read/28925890/the-use-of-hemodynamic-and-cerebral-monitoring-to-study-pharmacodynamics-in-neonates
#16
A Smits, L Thewissen, A Dereymaeker, E Dempsey, A Caicedo, G Naulaers
BACKGROUND: Drugs acting on the cardiovascular and central nervous system often display relatively fast clinical responses, which may differ in neonates compared to children and adults. Introduction of bedside monitoring tools might be of additional value in the pharmacodynamic (PD) assessment of such drugs in neonates. METHODS: We aim to provide an overview of the frequently used monitoring tools to assess drug effects on the hemodynamic status as well as the cerebral circulation, oxygenation and cerebral metabolism in neonates...
2017: Current Pharmaceutical Design
https://www.readbyqxmd.com/read/28819737/further-controversies-about-brain-tissue-oxygenation-pressure-reactivity-after-traumatic-brain-injury
#17
Morten Andresen, Joseph Donnelly, Marcel Aries, Marianne Juhler, David Menon, Pja Hutchinson, Peter Smielewski
BACKGROUND: Continuous monitoring of cerebral autoregulation is considered clinically useful due to its ability to warn against brain ischemic insults, which may translate to a relationship with adverse outcome. It is typically performed using the pressure reactivity index (PRx) based on mean arterial pressure and intracranial pressure. A new ORx index based on brain tissue oxygenation and cerebral perfusion pressure (CPP) has been proposed that similarly allows for evaluation of cerebrovascular reactivity...
August 17, 2017: Neurocritical Care
https://www.readbyqxmd.com/read/28782872/the-role-of-vascular-resistance-in-bold-responses-to-progressive-hypercapnia
#18
James Duffin, Olivia Sobczyk, Adrian Crawley, Julien Poublanc, Lashmi Venkatraghavan, Kevin Sam, Alan Mutch, David Mikulis, Joseph Fisher
The ability of the cerebral vasculature to regulate vascular diameter, hence resistance and cerebral blood flow (CBF), in response to metabolic demands (neurovascular coupling), and perfusion pressure changes (autoregulation) may be assessed by measuring the CBF response to carbon dioxide (CO2 ). In healthy individuals, the CBF response to a ramp CO2 stimulus from hypocapnia to hypercapnia is assumed sigmoidal or linear. However, other response patterns commonly occur, especially in individuals with cerebrovascular disease, and these remain unexplained...
August 7, 2017: Human Brain Mapping
https://www.readbyqxmd.com/read/28668343/changes-in-arterial-cerebral-blood-volume-during-lower-body-negative-pressure-measured-with-mri
#19
Joseph R Whittaker, Molly G Bright, Ian D Driver, Adele Babic, Sharmila Khot, Kevin Murphy
Cerebral Autoregulation (CA), defined as the ability of the cerebral vasculature to maintain stable levels of blood flow despite changes in systemic blood pressure, is a critical factor in neurophysiological health. Magnetic resonance imaging (MRI) is a powerful technique for investigating cerebrovascular function, offering high spatial resolution and wide fields of view (FOV), yet it is relatively underutilized as a tool for assessment of CA. The aim of this study was to demonstrate the potential of using MRI to measure changes in cerebrovascular resistance in response to lower body negative pressure (LBNP)...
June 28, 2017: NeuroImage
https://www.readbyqxmd.com/read/28657491/novel-noninvasive-method-of-cerebrovascular-blood-volume-assessment-using-brain-bioimpedance
#20
Mohamad H Tiba, Brendan M McCracken, Sardar Ansari, Ashwin Belle, Brandon C Cummings, Venkatakrishna Rajajee, Parag G Patil, Hasan B Alam, Kevin R Ward
Cerebrovascular autoregulation (CAR) is the ability of vessels to modulate their tone in response to changes in pressure. As an auto-protective mechanism, CAR is critical in preventing secondary brain injury post-trauma. Monitoring of changes in cerebral blood volume might be valuable in evaluating CAR and response to various therapies. In this study, we utilized an ocular-brain bioimpedance interface to assess real time changes in cerebral blood volume in response to a number of physiological challenges. We hypothesize that changes in brain bioimpedance (dz) would track changes in cerebral blood volume...
November 15, 2017: Journal of Neurotrauma
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