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Cerebral autoregulation

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https://www.readbyqxmd.com/read/28727580/increase-in-intracranial-pressure-by-application-of-a-rigid-cervical-collar-a-pilot-study-in-healthy-volunteers
#1
Iscander M Maissan, Rein Ketelaars, Boris Vlottes, Sanne E Hoeks, Dennis den Hartog, Robert J Stolker
OBJECTIVES: Rigid cervical collars are known to increase intracranial pressure (ICP) in severe traumatic brain injury (TBI). Cerebral blood flow might decrease according to the Kellie Monroe doctrine. For this reason, the use of the collar in patients with severe TBI has been abandoned from several trauma protocols in the Netherlands. There is no evidence on the effect of a rigid collar on ICP in patients with mild or moderate TBI or indeed patients with no TBI. As a first step we tested the effect in healthy volunteers with normal ICPs and intact autoregulation of the brain...
July 19, 2017: European Journal of Emergency Medicine: Official Journal of the European Society for Emergency Medicine
https://www.readbyqxmd.com/read/28719038/static-cerebrovascular-pressure-autoregulation-remains-intact-during-deep-hypothermia
#2
Dheeraj Goswami, Katherine McLeod, Samantha Leonard, Kathleen Kibler, Ronald Blaine Easley, Charles D Fraser, Dean Andropoulos, Ken Brady
BACKGROUND: Clinical studies measuring cerebral blood flow in infants during deep hypothermia have demonstrated diminished cerebrovascular pressure autoregulation. The coexistence of hypotension in these cohorts confounds the conclusion that deep hypothermia impairs cerebrovascular pressure autoregulation. AIM: We sought to compare the lower limit of autoregulation and the static rate of autoregulation between normothermic and hypothermic piglets. METHODS: Twenty anesthetized neonatal piglets (5-7 days old; 10 normothermic and 10 hypothermic to 20°C) had continuous measurements of cortical red cell flux using laser Doppler flowmetry, while hemorrhagic hypotension was induced without cardiopulmonary bypass...
July 18, 2017: Paediatric Anaesthesia
https://www.readbyqxmd.com/read/28699412/pressure-autoregulation-measurement-techniques-in-adult-tbi-part-ii-a-scoping-review-of-continuous-methods
#3
Frederick Adam Zeiler, Joseph Donnelly, Leanne Calviello, Peter Smieleweski, David Menon, Marek Czosnyka
To perform systematically a scoping review of the literature on commonly described continuous autoregulation measurement techniques in adult TBI. The goal was to provide an overview of methodology and comprehensive reference library of the available literature for each technique. Five separate small systematic reviews were conducted for each of the continuous techniques: pressure reactivity index (PRx), laser Doppler flowmetry (LDF), near infrared spectroscopy (NIRS) techniques, brain tissue oxygen tension (PbtO2), and thermal diffusion (TD) techniques...
July 12, 2017: Journal of Neurotrauma
https://www.readbyqxmd.com/read/28694108/increased-blood-pressure-variability-upon-standing-up-improves-reproducibility-of-cerebral-autoregulation-indices
#4
Adam Mahdi, Dragana Nikolic, Anthony A Birch, Mette S Olufsen, Ronney B Panerai, David M Simpson, Stephen J Payne
Dynamic cerebral autoregulation, that is the transient response of cerebral blood flow to changes in arterial blood pressure, is currently assessed using a variety of different time series methods and data collection protocols. In the continuing absence of a gold standard for the study of cerebral autoregulation it is unclear to what extent does the assessment depend on the choice of a computational method and protocol. We use continuous measurements of blood pressure and cerebral blood flow velocity in the middle cerebral artery from the cohorts of 18 normotensive subjects performing sit-to-stand manoeuvre...
July 7, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28694107/effects-of-non-physiological-blood-pressure-artefacts-on-cerebral-autoregulation
#5
Adam Mahdi, Erica M Rutter, Stephen J Payne
Cerebral autoregulation refers to the brain's regulation mechanisms that aim to maintain the cerebral blood flow approximately constant. It is often assessed by the autoregulation index (ARI). ARI uses arterial blood pressure and cerebral blood flow velocity time series to produce a ten-scale index of autoregulation performance (0 denoting the absence of and 9 the strongest autoregulation). Unfortunately, data are rarely free from various artefacts. Here, we consider four of the most common non-physiological blood pressure artefacts (saturation, square wave, reduced pulse pressure and impulse) and study their effects on ARI for a range of different artefact sizes...
July 7, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28681121/indexes-of-cerebral-autoregulation-do-not-reflect-impairment-in-syncope-insights-from-head-up-tilt-test-of-vasovagal-and-autonomic-failure-subjects
#6
Pedro Castro, João Freitas, Rosa Santos, Ronney Panerai, Elsa Azevedo
PURPOSE: The study of dynamic cerebral autoregulation (CA), which adapts cerebral blood flow to arterial blood pressure (ABP) fluctuations, has been limited in orthostatic intolerance syndromes, mainly due to its stationary prerequisites hardly to meet during maneuvers to provoke syncope itself. New techniques of continuous estimates of CA could overcome this pitfall. We aimed to evaluate CA during head-up tilt test in common conditions causing syncope. METHODS: We compared three groups: eight controls; eight patients with autonomic failure due to familial amyloidotic polyneuropathy; eight patients with vasovagal syncope (VVS)...
July 5, 2017: European Journal of Applied Physiology
https://www.readbyqxmd.com/read/28674514/aspects-on-the-physiological-and-biochemical-foundations-of-neurocritical-care
#7
REVIEW
Carl-Henrik Nordström, Lars-Owe Koskinen, Magnus Olivecrona
Neurocritical care (NCC) is a branch of intensive care medicine characterized by specific physiological and biochemical monitoring techniques necessary for identifying cerebral adverse events and for evaluating specific therapies. Information is primarily obtained from physiological variables related to intracranial pressure (ICP) and cerebral blood flow (CBF) and from physiological and biochemical variables related to cerebral energy metabolism. Non-surgical therapies developed for treating increased ICP are based on knowledge regarding transport of water across the intact and injured blood-brain barrier (BBB) and the regulation of CBF...
2017: Frontiers in Neurology
https://www.readbyqxmd.com/read/28673505/the-first-sign-of-loss-of-consciousness
#8
B S Typ Whinnery, Estrella M Forster
The first clinically observable sign of an unconsciousness episode (UNCE) serves as the temporal sequence (kinetics) onset point for neurological events occurring during the loss of consciousness, unconsciousness and recovery of consciousness phases of the UNCE. The initial neurologic signs of 212 individuals exposed to gradual (N=114) and rapid (N=98) onset +Gz acceleration stress, inducing the ischemic LOC phase in 83.3±18.6s and 8.89±1.52s; p<0.001respectively, were determined. The duration of the unconscious phase (considered absolute incapacitation) was 10...
June 30, 2017: Physiology & Behavior
https://www.readbyqxmd.com/read/28673382/rational-use-of-dopamine-in-hypotensive-newborns-improving-our-understanding-of-the-effect-on-cerebral-autoregulation
#9
Vibeke Ramsgaard Eriksen
Hypotension in critically ill newborn infants is associated with higher mortality and higher risk of cerebral injuries. Yet treating hypotension has never been shown to improve outcomes. In fact, some studies have found that hypotensive newborn infants who were treated with dopamine fared worse than a comparable group of newborn infants who were not. Therefore, a concern has been raised that dopamine might cause the observed adverse outcomes. Cerebral autoregulation is a protective mechanism that maintains a fairly constant cerebral blood flow despite fluctuations in blood pressure...
July 2017: Danish Medical Journal
https://www.readbyqxmd.com/read/28668343/changes-in-arterial-cerebral-blood-volume-during-lower-body-negative-pressure-measured-with-mri
#10
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/28664392/validation-of-near-infrared-spectroscopy-for-monitoring-cerebral-autoregulation-in-comatose-patients
#11
Lucia Rivera-Lara, Romergryko Geocadin, Andres Zorrilla-Vaca, Ryan Healy, Batya R Radzik, Caitlin Palmisano, Marek Mirski, Wendy C Ziai, Charles Hogue
BACKGROUND: Transcranial Doppler (TCD) noninvasively measures cerebral blood flow (CBF) velocity and is a well-studied method to monitor cerebral autoregulation (CA). Near-infrared spectroscopy (NIRS) has emerged as a promising noninvasive method to determine CA continuously by using regional cerebral oxygen saturation (rSO2) as a surrogate for CBF. Little is known about its accuracy to determine CA in patients with intracranial lesions. The purpose of this study was to assess the accuracy of rSO2-based CA monitoring with TCD methods in comatose patients with acute neurological injury...
June 29, 2017: Neurocritical Care
https://www.readbyqxmd.com/read/28657491/novel-noninvasive-method-of-cerebrovascular-blood-volume-assessment-using-brain-bioimpedance
#12
Mohamad Hakam Tiba, Brendan M McCracken, Sardar Ansari, Ashwin Belle, Brandon C Cummings, Venkatakrishna Rajajee, Parag G Patil, Hasan B Alam, Kevin R Ward
Cerebro-vascular autoregulation (CAR) is the ability of vessels to modulate their tone in response to changes in pressure. CAR, as an auto-protective mechanism 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 physiologic challenges. We hypothesize that changes in brain bioimpedance (dz) would track changes in cerebral blood volume...
June 28, 2017: Journal of Neurotrauma
https://www.readbyqxmd.com/read/28656320/rho-kinase-and-the-nitric-oxide-pathway-modulate-basilar-arterial-reactivity-to-acetylcholine-and-angiotensin-ii-in-streptozotocin-induced-diabetic-mice
#13
Md Zahorul Islam, Cuong Van Dao, Atsushi Miyamoto, Mitsuya Shiraishi
Diabetes mellitus comprises a heterogeneous group of metabolic disorders with underlying hyperglycemia and secondary cardiovascular complications. Growing evidence suggests that vascular dysfunction is among the most important causes of diabetic cardiovascular disease. Therefore, we determined whether streptozotocin (STZ)-induced diabetes in mice affects blood pressure and cerebral arterial responsiveness to angiotensin (Ang) II and acetylcholine (ACh), which are important modulators of cerebrovascular autoregulation...
June 27, 2017: Naunyn-Schmiedeberg's Archives of Pharmacology
https://www.readbyqxmd.com/read/28655446/cerebral-autoregulation-making-sense-of-the-nonsensical
#14
EDITORIAL
Ken M Brady, Carlos M Mery
No abstract text is available yet for this article.
May 31, 2017: Journal of Thoracic and Cardiovascular Surgery
https://www.readbyqxmd.com/read/28653463/does-hypothermia-impair-cerebrovascular-autoregulation-in-neonates-during-cardiopulmonary-bypass
#15
Brendan Smith, Eric Vu, Kathleen Kibler, Craig Rusin, Ronald B Easley, Dean Andropoulos, Jeffrey Heinle, Marek Czosnyka, Daniel Licht, Jennifer Lynch, Ken Brady
BACKGROUND: Autoregulation monitoring has been proposed as a means to identify optimal arterial blood pressure goals during cardiopulmonary bypass, but it has been observed that cerebral blood flow is pressure passive during hypothermic bypass. When neonates cooled during cardiopulmonary bypass are managed with vasodilators and controlled hypotension, it is not clear whether hypothermia or hypotension were the cause of impaired autoregulation. AIM: We sought to measure the effect of both arterial blood pressure and hypothermia on autoregulation in a cohort of infants cooled for bypass, hypothesizing a collinear relationship between hypothermia, hypotension, and dysautoregulation...
June 27, 2017: Paediatric Anaesthesia
https://www.readbyqxmd.com/read/28648106/pressure-autoregulation-measurement-techniques-in-adult-tbi-part-i-a-scoping-review-of-intermittent-semi-intermittent-methods
#16
Frederick Adam Zeiler, Joseph Donnelly, Leanne Calviello, David Menon, Peter Smieleweski, Marek Czosnyka
To perform a systematic, scoping review of commonly described intermittent/semi-intermittent autoregulation measurement techniques in adult TBI. Nine separate systematic reviews were conducted for each intermittent technique: Computed tomographic perfusion (CTP)/Xenon-CT (Xe-CT), positron emission tomography (PET), magnetic resonance imaging (MRI), arterio-venous difference in oxygen (AVDO2) technique, thigh cuff deflation technique (TCDT), transient hyperemic response test (THRT), orthostatic hypotension test (OHT), mean flow index (Mx) and transfer function ARI (TF-ARI)...
June 24, 2017: Journal of Neurotrauma
https://www.readbyqxmd.com/read/28643998/survey-in-expert-clinicians-on-validity-of-automated-calculation-of-optimal-cerebral-perfusion-pressure
#17
Romy Steijn, Roy Stewart, Marek Czosnyka, Joseph Donnelly, Ari Ercole, Antony Absalom, Jan W Elting, Christina Haubrich, Peter Smielewski, Marcel Aries
BACKGROUND: Optimal cerebral perfusion pressure (CPPopt) targeting in traumatic brain injury (TBI) patients constitutes an active and controversial area of research. It has been suggested that an autoregulation guided CPP therapy may improve TBI outcome. Prerequisites of a CPPopt intervention study would be objective criteria for the CPPopt detection.. This study compared the agreement between automated and visual CPPopt detection. METHODS: Twenty-five clinicians from 18 centres worldwide, familiar with brain monitoring and using dedicated software, reviewed ten 4-hour CPPopt screenshots at 48 hrs after ictus in selected TBI patients...
June 22, 2017: Minerva Anestesiologica
https://www.readbyqxmd.com/read/28642293/random-squat-stand-maneuvers-a-novel-approach-for-assessment-of-dynamic-cerebral-autoregulation
#18
Sam C Barnes, Naomi Ball, Victoria Joanna Haunton, Ronney B Panerai, Thompson G Robinson
BACKGROUND: Squat-stand maneuvers (SSM) have been used to assess dynamic cerebral autoregulation (dCA), but always at a fixed-frequency (FF). This study aimed to assess the use of random-frequency (RF) SSMs as a stimulus for measuring dCA, and to determine the reproducibility of FF and RFSSMs. METHOD: 29 healthy volunteers (19 male, mean age 23.0 [4.9] years) completed the study; 11 returned for a repeat visit (median 45 days). Heart rate, beat-to-beat blood pressure, middle cerebral artery (MCA) blood flow velocity, end-tidal CO2 and angle of the squat movement were measured...
June 22, 2017: Journal of Applied Physiology
https://www.readbyqxmd.com/read/28639837/measuring-cerebrovascular-autoregulation-in-preterm-infants-using-near-infrared-spectroscopy-an-overview-of-the-literature
#19
Elisabeth M W Kooi, Elise A Verhagen, Jan Willem J Elting, Marek Czosnyka, Topun Austin, Flora Y Wong, Marcel J H Aries
The preterm born infant's ability to regulate its cerebral blood flow (CBF) is crucial in preventing secondary ischemic and hemorrhagic damage in the developing brain. The relationship between arterial blood pressure (ABP) and CBF estimates, such as regional cerebral oxygenation as measured by near-infrared spectroscopy (NIRS), is an attractive option for continuous non-invasive assessment of cerebrovascular autoregulation. Areas covered: The authors performed a literature search to provide an overview of the current literature on various current clinical practices and methods to measure cerebrovascular autoregulation in the preterm infant by NIRS...
June 29, 2017: Expert Review of Neurotherapeutics
https://www.readbyqxmd.com/read/28634025/impaired-cerebral-autoregulation-in-preoperative-newborn-infants-with-congenital-heart-disease
#20
Jodie K Votava-Smith, Christopher J Statile, Michael D Taylor, Eileen C King, Jesse M Pratt, David P Nelson, Erik C Michelfelder
OBJECTIVES: To characterize cerebral autoregulation (CA) in preoperative newborn infants with congenital heart disease (CHD). METHODS: This was a prospective, pilot study of term newborns with CHD who required intensive care. Continuous mean arterial blood pressure (MAP), cerebral tissue oxygen saturation (SCTO2) via near-infrared spectroscopy, and arterial oxygen saturation (SaO2) were collected. Significant low-frequency coherence between MAP and SCTO2 was used to define impaired CA in 20-minute epochs...
May 23, 2017: Journal of Thoracic and Cardiovascular Surgery
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