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Payne SJ. Dynamic cerebral autoregulation is governed by two time constants: Arterial transit time and feedback time constant. J Physiol 2024; 602:1953-1966. [PMID: 38630963 DOI: 10.1113/jp285679] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Accepted: 03/21/2024] [Indexed: 04/19/2024] Open
Abstract
Dynamic cerebral autoregulation (dCA) is the mechanism that describes how the brain maintains cerebral blood flow approximately constant in response to short-term changes in arterial blood pressure. This is known to be impaired in many different pathological conditions, including ischaemic and haemorrhagic stroke, dementia and traumatic brain injury. Many different approaches have thus been used both to analyse and to quantify this mechanism in a range of healthy and diseased subjects, including data-driven models (in both the time and the frequency domain) and biophysical models. However, despite the substantial body of work on both biophysical models and data-driven models of dCA, there remains little work that links the two together. One of the reasons for this is proposed to be the discrepancies between the time constants that govern dCA in models and in experimental data. In this study, the processes that govern dCA are examined and it is proposed that the application of biophysical models remains limited due to a lack of understanding about the physical processes that are being modelled, partly due to the specific model formulation that has been most widely used (the equivalent electrical circuit). Based on the analysis presented here, it is proposed that the two most important time constants are arterial transit time and feedback time constant. It is therefore time to revisit equivalent electrical circuit models of dCA and to develop a more physiologically realistic alternative, one that can more easily be related to experimental data. KEY POINTS: Dynamic cerebral autoregulation is governed by two time constants. The first time constant is the arterial transit time, rather than the traditional 'RC' time constant widely used in previous models. This arterial transit time is approximately 1 s in the brain. The second time constant is the feedback time constant, which is less accurately known, although it is somewhat larger than the arterial transit time. The equivalent electrical circuit model of dynamic cerebral autoregulation should be replaced with a more physiologically representative model.
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Affiliation(s)
- Stephen J Payne
- Institute of Applied Mechanics, National Taiwan University, Taipei, Taiwan
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2
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Olsen MH, Riberholt CG, Berg RMG, Møller K. Myths and methodologies: Assessment of dynamic cerebral autoregulation by the mean flow index. Exp Physiol 2024; 109:614-623. [PMID: 38376110 PMCID: PMC10988760 DOI: 10.1113/ep091327] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Accepted: 01/17/2024] [Indexed: 02/21/2024]
Abstract
The mean flow index-usually referred to as Mx-has been used for assessing dynamic cerebral autoregulation (dCA) for almost 30 years. However, concerns have arisen regarding methodological consistency, construct and criterion validity, and test-retest reliability. Methodological nuances, such as choice of input (cerebral perfusion pressure, invasive or non-invasive arterial pressure), pre-processing approach and artefact handling, significantly influence mean flow index values, and previous studies correlating mean flow index with other established dCA metrics are confounded by inherent methodological flaws like heteroscedasticity, while the mean flow index also fails to discriminate individuals with presumed intact versus impaired dCA (discriminatory validity), and its prognostic performance (predictive validity) across various conditions remains inconsistent. The test-retest reliability, both within and between days, is generally poor. At present, no single approach for data collection or pre-processing has proven superior for obtaining the mean flow index, and caution is advised in the further use of mean flow index-based measures for assessing dCA, as current evidence does not support their clinical application.
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Affiliation(s)
- Markus Harboe Olsen
- Department of Neuroanaesthesiology, The Neuroscience CentreCopenhagen University Hospital − RigshospitaletCopenhagenDenmark
| | - Christian Gunge Riberholt
- Department of Neuroanaesthesiology, The Neuroscience CentreCopenhagen University Hospital − RigshospitaletCopenhagenDenmark
- Department of Brain and Spinal Cord Injury, The Neuroscience CentreCopenhagen University Hospital − RigshospitaletCopenhagenDenmark
| | - Ronan M. G. Berg
- Department of Clinical Physiology and Nuclear MedicineCopenhagen University Hospital − RigshospitaletCopenhagenDenmark
- Centre for Physical Activity ResearchCopenhagen University Hospital − RigshospitaletCopenhagenDenmark
- Department of Biomedical Sciences, Faculty of Health and Medical SciencesUniversity of CopenhagenCopenhagenDenmark
- Neurovascular Research Laboratory, Faculty of Life Sciences and EducationUniversity of South WalesPontypriddUK
| | - Kirsten Møller
- Department of Neuroanaesthesiology, The Neuroscience CentreCopenhagen University Hospital − RigshospitaletCopenhagenDenmark
- Department of Clinical Medicine, Faculty of Health and Medical SciencesUniversity of CopenhagenCopenhagenDenmark
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Morales-Rojas C, Panerai RB, Jara JL. Exploring Physiological Differences in Brain Areas Using Statistical Complexity Analysis of BOLD Signals. Entropy (Basel) 2024; 26:81. [PMID: 38248206 DOI: 10.3390/e26010081] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2023] [Revised: 01/03/2024] [Accepted: 01/08/2024] [Indexed: 01/23/2024]
Abstract
The brain is a fundamental organ for the human body to function properly, for which it needs to receive a continuous flow of blood, which explains the existence of control mechanisms that act to maintain this flow as constant as possible in a process known as cerebral autoregulation. One way to obtain information on how the levels of oxygen supplied to the brain vary is through of BOLD (Magnetic Resonance) images, which have the advantage of greater spatial resolution than other forms of measurement, such as transcranial Doppler. However, they do not provide good temporal resolution nor allow for continuous prolonged examination. Thus, it is of great importance to find a method to detect regional differences from short BOLD signals. One of the existing alternatives is complexity measures that can detect changes in the variability and temporal organisation of a signal that could reflect different physiological states. The so-called statistical complexity, created to overcome the shortcomings of entropy alone to explain the concept of complexity, has shown potential with haemodynamic signals. The aim of this study is to determine by using statistical complexity whether it is possible to find differences between physiologically distinct brain areas in healthy individuals. The data set includes BOLD images of 10 people obtained at the University Hospital of Leicester NHS Trust with a 1.5 Tesla magnetic resonance imaging scanner. The data were captured for 180 s at a frequency of 1 Hz. Using various combinations of statistical complexities, no differences were found between hemispheres. However, differences were detected between grey matter and white matter, indicating that these measurements are sensitive to differences in brain tissues.
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Affiliation(s)
- Catalina Morales-Rojas
- Departamento de Ingeniería Informática, Facultad de Ingeniería, Universidad de Santiago de Chile, Santiago 9170022, Chile
| | - Ronney B Panerai
- Department of Cardiovascular Sciences, University of Leicester, Leicester LE1 7RH, UK
- NIHR Leicester Biomedical Research Centre, British Heart Foundation Cardiovascular Research Centre, Glenfield Hospital, Leicester LE3 9QP, UK
| | - José Luis Jara
- Departamento de Ingeniería Informática, Facultad de Ingeniería, Universidad de Santiago de Chile, Santiago 9170022, Chile
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Vidyashree M, Deepeshwar S, K MN, Kaligal C, Kanthi A, Krishna D, Raghuram N, Bathala L, Sharma VK. Cerebral Haemodynamic Changes in Type 2 Diabetes Mellitus Following a Three-Month Yoga Intervention: A Randomized Controlled Trial. Cureus 2024; 16:e51548. [PMID: 38313913 PMCID: PMC10835018 DOI: 10.7759/cureus.51548] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/02/2024] [Indexed: 02/06/2024] Open
Abstract
Background and purpose Cerebral haemodynamics and cognitive performance may be adversely affected in type 2 diabetes mellitus (T2DM). Previous studies reported reduced cerebral blood flow (CBF) and altered cerebrovascular reactivity (CVR) in T2DM. Yoga, an ancient holistic health approach, is known to be beneficial for T2DM. We hypothesized that yoga practice may alter CBF and the flow resistance in the middle cerebral artery (MCA) and improve cognition in T2DM. Our secondary objective was to explore the relationship between changes in cerebral haemodynamics and cognition in T2DM. Materials and methods Participants were randomly allotted into the yoga and control groups based on the eligibility criteria. One hour of yoga intervention specific to type 2 diabetes was provided to the yoga group for three months, while conventional treatment was provided to the control group. A transcranial Doppler was used to evaluate longitudinal changes in cerebral haemodynamics in MCA. A Corsi block tapping test was used to assess visio-spatial working memory. Results There were 75 participants recruited, of whom 38 participated in yoga and 37 participated in a control group. Both intention to treat and per protocol analysis showed significant results. At day 90, intention-to-treat analysis showed significant changes in CBF velocities (mean difference -10.85%, 95% CI (-13.26, -6.15), p<0.001), cerebral vasodilatory reserve (mean difference -0.23%, 95% CI (-0.43, -0.03), p=0.02) and cognition (mean difference -12.13%, 95% CI (-17.48, -6.78), p≤0.001). There was no between-group effect. Also, the correlation between the CBF and cognition did not show any significant results. Conclusion The three-month yoga intervention was associated with an improvement in cerebral hemodynamics. The study also revealed an improvement in visio-spatial working memory among patients with T2DM. The study did not show any correlation between the improvement in cerebral haemodynamics and working memory. We recommend larger and longer studies on yoga intervention for T2DM patients to evaluate whether such benefits are sustained and improve their quality of life.
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Affiliation(s)
- Mahadevappa Vidyashree
- Department of Yoga and Life Sciences, Swami Vivekananda Yoga Anusandhana Samsthana, Deemed to be University, Bangalore, IND
| | - Singh Deepeshwar
- Department of Yoga and Life Sciences, Swami Vivekananda Yoga Anusandhana Samsthana, Bengaluru, IND
- Department of Yoga, Babasaheb Bhimrao Ambedkar University, Lucknow, IND
| | - Manjunath N K
- Department of Yoga and Life Sciences, Swami Vivekananda Yoga Anusandhana Samsthana, Bangalore, IND
| | - Chidananda Kaligal
- Department of Yoga and Life Sciences, Swami Vivekananda Yoga Anusandhana Samsthana, Bangalore, IND
| | - Amit Kanthi
- Department of Yoga and Life Sciences, Swami Vivekananda Yoga Anusandhana Samsthana, Bangalore, IND
| | - Dwivedi Krishna
- Department of Yoga and Life Sciences, Swami Vivekananda Yoga Anusandhana Samsthana, Bangalore, IND
| | - Nagarathna Raghuram
- Department of Yoga and Life Sciences, Swami Vivekananda Yoga Anusandhana Samsthana, Bangalore, IND
| | | | - Vijay K Sharma
- Department of Neurology, Yong Loo Lin School of Medicine, Singapore, SGP
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Kostoglou K, Simpson DM, Payne SJ. Point/counterpoint: We should not take the direction of blood pressure change into consideration for dynamic cerebral autoregulation quantification. J Cereb Blood Flow Metab 2022; 42:2354-2356. [PMID: 36113047 PMCID: PMC9670004 DOI: 10.1177/0271678x221123442] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Over the past years, a wide range of studies have provided evidence of asymmetry in the response of static and dynamic cerebral autoregulation (CA) during increasing and decreasing pressure challenges. The main message is that CA is stronger during transient increases of arterial blood pressure rather than decreases. Here we do not argue against the presence of CA asymmetry but we seek to raise questions regarding the measurement of the effect and whether this effect needs to be taken into account, especially in clinical settings.
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Affiliation(s)
- Kyriaki Kostoglou
- Institute of Neural Engineering, Graz University of Technology, Graz, Austria
| | - David M Simpson
- ISVR, Faculty of Engineering and the Environment, University of Southampton, Southampton, UK
| | - Stephen J Payne
- Institute of Applied Mechanics, National Taiwan University, Taipei
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Howard R, Li R, Harvey-Jones K, Verma V, Lange F, Boylan G, Tachtsidis I, Mitra S. Optical Monitoring in Neonatal Seizures. Cells 2022; 11:2602. [PMID: 36010678 DOI: 10.3390/cells11162602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Revised: 07/30/2022] [Accepted: 08/16/2022] [Indexed: 11/17/2022] Open
Abstract
BACKGROUND Neonatal seizures remain a significant cause of morbidity and mortality worldwide. The past decade has resulted in substantial progress in seizure detection and understanding the impact seizures have on the developing brain. Optical monitoring such as cerebral near-infrared spectroscopy (NIRS) and broadband NIRS can provide non-invasive continuous real-time monitoring of the changes in brain metabolism and haemodynamics. AIM To perform a systematic review of optical biomarkers to identify changes in cerebral haemodynamics and metabolism during the pre-ictal, ictal, and post-ictal phases of neonatal seizures. METHOD A systematic search was performed in eight databases. The search combined the three broad categories: (neonates) AND (NIRS) AND (seizures) using the stepwise approach following PRISMA guidance. RESULTS Fifteen papers described the haemodynamic and/or metabolic changes observed with NIRS during neonatal seizures. No randomised controlled trials were identified during the search. Studies reported various changes occurring in the pre-ictal, ictal, and post-ictal phases of seizures. CONCLUSION Clear changes in cerebral haemodynamics and metabolism were noted during the pre-ictal, ictal, and post-ictal phases of seizures in neonates. Further studies are necessary to determine whether NIRS-based methods can be used at the cot-side to provide clear pathophysiological data in real-time during neonatal seizures.
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Marshall RA, Luchkanych AMS, Morton JS, Boyes NG, Zhai A, Marciniuk DD, Mei Y, Allison EY, Shoemaker JK, Al-Khazraji BK, Allen MD, Tomczak CR, Olver TD. Cerebral haemodynamics during arrhythmia in health, ischaemic heart disease and heart failure with reduced ejection fraction, and in a preclinical swine model. J Physiol 2022; 600:2311-2325. [PMID: 35389526 DOI: 10.1113/jp283112] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Accepted: 04/04/2022] [Indexed: 12/29/2022] Open
Abstract
Ventricular arrhythmias are associated with neurological impairment and could represent a source of cerebral hypoperfusion. In the present study, data from healthy individuals (n = 11), patients with ischaemic heart disease (IHD; ejection fraction >40%; n = 9) and patients with heart failure with reduced ejection fraction (HFrEF; EF = 31 (5)%, n = 11), as well as data from swine surgeries, where spontaneous ventricular arrhythmias were observed during cerebrovascular examination (transcranial Doppler ultrasound in humans and laser Doppler in swine) were analysed retrospectively to investigate the effect of arrhythmia on cerebral microvascular haemodynamics. A subset of participants also completed the Montreal Cognitive Assessment (MoCA). Middle cerebral artery mean blood velocity (MCAVmean ) decreased during premature ventricular contraction (PVC) in all groups, and data from swine indicate PVCs reduced cerebral microvascular perfusion. Overall MCAVmean was decreased in the HFrEF vs. control group. Further, %∆MCAVmean /%∆mean arterial pressure during the PVC was greater in the HFrEF vs. control group and was correlated with decreased MoCA scores. Subanalysis of HFrEF data revealed that during bigeminy MCAVmean decreased owing to reductions during irregular beats only. During non-sustained ventricular tachycardia, MCAVmean decreased but recovered above baseline upon return to sinus rhythm. Also, haemodynamic perturbations during and following the PVC were greater in the brachial artery vs. the MCA. Therefore, ventricular arrhythmias decreased indices of cerebral perfusion irrespective of IHD or HFrEF. The relative magnitude of arrhythmia-induced haemodynamic perturbations appears to be population specific and arrhythmia type and organ dependent. The cumulative burden of arrhythmia-induced deficits may exacerbate existing cerebral hypoperfusion in HFrEF and contribute to neurological abnormalities in this population. KEY POINTS: Irregular heartbeats are often considered benign in isolation, but individuals who experience them frequently have a higher prevalence of cerebrovascular and/or cognitive associated disorders. How irregular heartbeats affect blood pressure and cerebral haemodynamics in healthy and cardiovascular disease patients, those with and without reduced ejection fraction, remains unknown. Here it was found that in the absence of symptoms associated with irregular heartbeats, such as dizziness or hypotension, single, multiple non-sustained and sustained irregular heartbeats influence cerebral haemodynamics in a population-specific, arrhythmia-type and organ-dependent manner. Relative deficits in the index of cerebral blood flow normalized to relative deficits in blood pressure were greatest in patients with heart failure with reduced ejection and inversely related with cognitive performance. Chronic arrhythmias may exacerbate existing cerebral hypoperfusion in heart failure with reduced ejection fraction, thereby providing a mechanistic link between otherwise benign irregular heartbeats and cognitive dysfunction, independent of embolism.
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Affiliation(s)
- Rory A Marshall
- Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Adam M S Luchkanych
- Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Jude S Morton
- Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Natasha G Boyes
- College of Kinesiology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Alexander Zhai
- College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Darcy D Marciniuk
- College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Yixue Mei
- Department of Kinesiology, Faculty of Science, McMaster University, Hamilton, Ontario, Canada
| | - Elric Y Allison
- Department of Kinesiology, Faculty of Science, McMaster University, Hamilton, Ontario, Canada
| | | | - Baraa K Al-Khazraji
- Department of Kinesiology, Faculty of Science, McMaster University, Hamilton, Ontario, Canada
| | - Matti D Allen
- Department of Physical Medicine and Rehabilitation, School of Medicine, Queen's University, Kingston, Ontario, Canada
| | - Corey R Tomczak
- College of Kinesiology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - T Dylan Olver
- Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
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Beishon LC, Minhas JS. Cerebral Autoregulation and Neurovascular Coupling in Acute and Chronic Stroke. Front Neurol 2021; 12:720770. [PMID: 34539560 PMCID: PMC8446264 DOI: 10.3389/fneur.2021.720770] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Accepted: 08/11/2021] [Indexed: 11/13/2022] Open
Affiliation(s)
- Lucy C. Beishon
- Department of Cardiovascular Sciences, University of Leicester, Leicester, United Kingdom
| | - Jatinder S. Minhas
- Department of Cardiovascular Sciences, University of Leicester, Leicester, United Kingdom
- National Institute for Health Research (NIHR) Leicester Biomedical Research Centre, British Heart Foundation Cardiovascular Research Centre, Glenfield Hospital, Leicester, United Kingdom
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Jara JL, Morales-Rojas C, Fernández-Muñoz J, Haunton VJ, Chacón M. Using complexity-entropy planes to detect Parkinson's disease from short segments of haemodynamic signals. Physiol Meas 2021; 42. [PMID: 34256359 DOI: 10.1088/1361-6579/ac13ce] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Accepted: 07/13/2021] [Indexed: 11/11/2022]
Abstract
Objective. There is emerging evidence that analysing the entropy and complexity of biomedical signals can detect underlying changes in physiology which may be reflective of disease pathology. This approach can be used even when only short recordings of biomedical signals are available. This study aimed to determine whether entropy and complexity measures can detect differences between subjects with Parkinsons disease and healthy controls (HCs).Approach. A method based on a diagram of entropy versus complexity, named complexity-entropy plane, was used to re-analyse a dataset of cerebral haemodynamic signals from subjects with Parkinsons disease and HCs obtained under poikilocapnic conditions. A probability distribution for a set of ordinal patterns, designed to capture regularities in a time series, was computed from each signal under analysis. Four types of entropy and ten types of complexity measures were estimated from these distributions. Mean values of entropy and complexity were compared and their classification power was assessed by evaluating the best linear separator on the corresponding complexity-entropy planes.Main results. Few linear separators obtained significantly better classification, evaluated as the area under the receiver operating characteristic curve, than signal mean values. However, significant differences in both entropy and complexity were detected between the groups of participants.Significance. Measures of entropy and complexity were able to detect differences between healthy volunteers and subjects with Parkinson's disease, in poikilocapnic conditions, even though only short recordings were available for analysis. Further work is needed to refine this promising approach, and to help understand the findings in the context of specific pathophysiological changes.
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Affiliation(s)
- J L Jara
- Departamento de Ingeniería Informática, Universidad de Santiago de Chile, Usach, Santiago, Chile
| | - Catalina Morales-Rojas
- Departamento de Ingeniería Informática, Universidad de Santiago de Chile, Usach, Santiago, Chile
| | - Juan Fernández-Muñoz
- Departamento de Ingeniería Informática, Universidad de Santiago de Chile, Usach, Santiago, Chile
| | - Victoria J Haunton
- Department of Cardiovascular Sciences, University of Leicester, Leicester, United Kingdom
| | - Max Chacón
- Departamento de Ingeniería Informática, Universidad de Santiago de Chile, Usach, Santiago, Chile
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Lefferts WK, Lefferts EC, Hibner BA, Smith KJ, Fernhall B. Impact of acute changes in blood pressure and arterial stiffness on cerebral pulsatile haemodynamics in young and middle-aged adults. Exp Physiol 2021; 106:1643-1653. [PMID: 33938052 DOI: 10.1113/ep089319] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2020] [Accepted: 04/28/2021] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? Does cerebrovascular pulsatility respond differently to acute increases in arterial stiffness in middle-aged compared with young adults? What is the main finding and its importance? Compared with young adults, middle-aged adults exhibited similar changes in cerebral pulsatile damping despite attenuated changes in carotid diameter and cerebrovascular pulsatility during blood pressure-dependent, but not blood pressure-independent, increases in large artery stiffness. ABSTRACT Acute manipulation of arterial stiffness through interventions that increase sympathetic activity might provoke cerebral pulsatility and damping and reveal whether cerebrovascular haemodynamics respond differently to transient elevations in arterial stiffness in middle-aged compared with young adults. We compared cerebral pulsatility and damping in middle-aged versus young adults during two different sympathetic interventions [cold pressor test (CP) and lower-body negative pressure (LBNP)] that increase arterial stiffness acutely. Cerebrovascular haemodynamics were assessed in 15 middle-aged (54 ± 7 years old; 11 female) and 15 sex-matched young adults (25 ± 4 years old) at rest and during the CP test (4 min, 6.4 ± 0.8°C) and LBNP (6 min, -20 mmHg). Mean blood pressure was measured continuously via finger photoplethysmography. Carotid-femoral pulse wave velocity (cfPWV) and carotid stiffness were measured via tonometry and ultrasound. Blood velocity pulsatility index (PI) was measured at the middle cerebral (MCA) and common carotid artery (CCA) using Doppler, with pulsatile damping calculated as CCA PI divided by MCA PI. Increases in cfPWV were driven by changes in mean pressure during CP but not during LBNP in both groups (P < 0.05). Pulsatile damping decreased in both groups (P < 0.05) despite reductions in MCA PI and greater carotid dilatation during CP in young compared with middle-aged adults (P < 0.05). Pressure-independent increases in cfPWV during LBNP did not alter pulsatile damping but decreased MCA PI in both young and middle-aged adults (P < 0.05). These data suggest that changes in carotid diameter and cerebrovascular pulsatility differ between young and middle-aged adults despite similar changes in cerebral pulsatile damping during blood pressure-dependent, but not blood pressure-independent, increases in large artery stiffness.
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Affiliation(s)
- Wesley K Lefferts
- Department of Kinesiology and Nutrition, University of Illinois at Chicago, Chicago, Illinois, USA.,Department of Kinesiology, Iowa State University, Ames, Iowa, USA
| | - Elizabeth C Lefferts
- Department of Kinesiology and Nutrition, University of Illinois at Chicago, Chicago, Illinois, USA
| | - Brooks A Hibner
- Department of Kinesiology and Nutrition, University of Illinois at Chicago, Chicago, Illinois, USA
| | - Kurt J Smith
- Department of Kinesiology and Nutrition, University of Illinois at Chicago, Chicago, Illinois, USA
| | - Bo Fernhall
- Department of Kinesiology and Nutrition, University of Illinois at Chicago, Chicago, Illinois, USA
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Sands E, Wong L, Lam MY, Panerai RB, Robinson TG, Minhas JS. The Effects of Gradual Change in Head Positioning on the Relationship between Systemic and Cerebral Haemodynamic Parameters in Healthy Controls and Acute Ischaemic Stroke Patients. Brain Sci 2020; 10:E582. [PMID: 32842651 DOI: 10.3390/brainsci10090582] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Revised: 08/17/2020] [Accepted: 08/20/2020] [Indexed: 11/27/2022] Open
Abstract
(1) Background: Larger blood pressure variability (BPv) in the first 3 h post-stroke onset increases pathophysiological effects such as infarct size, and leads to greater risk of disability, comorbidities and mortality at 90 days. However, there is limited information on the relationship between systemic and cerebral haemodynamic and variability parameters. (2) Objectives: This study determined the effect of a gradual change in head position (GHP) on cerebral blood flow velocity variability (CBFVv) and mean arterial blood pressure variability (MABPv), in healthy controls and acute ischaemic stroke (AIS) patients. Methods: CBFVv and MABPv were expressed as standard deviation (SD) and coefficient of variation. A total of 16 healthy controls (mean age 57 ± 16 years) were assessed over two visits, 12 ± 8 days apart, and 15 AIS patients (mean age 69 ± 8.5 years) were assessed over three visits (V1: 13.3 ± 6.9 h, V2: 4.9 ± 3.2 days and V3: 93.9 ± 11.5 days post-stroke). (3) Results: In response to GHP, MABPv does not initially increase, but over time MABPv showed a significant increase in response to GHP in AIS (visits 2 and 3) and controls (visit 2). Additionally, in response to GHP in AIS, CBFVv increased in the affected hemisphere. Lastly, in AIS, a significant correlation between CBFVv and MABPv, assessed by SD, was seen in the unaffected hemisphere, whereas this relationship was not demonstrated in the affected hemisphere. (4) Conclusions: To our knowledge, this is the first study to analyse the relationship between CBFVv and MABPv. Shedding light on the effect of head position on the relationship between cerebral blood flow and blood pressure is important to improve our understanding of the underlying effects of cerebral autoregulation impairment. This early mechanistic study provides evidence supporting supine head positioning in healthy controls and stroke patients, through demonstration of a reduction of MABPv and increase in CBFVv.
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Hougaard A, Younis S, Iljazi A, Haanes KA, Lindberg U, Vestergaard MB, Amin FM, Sugimoto K, Kruse LS, Ayata C, Ashina M. Cerebrovascular effects of endothelin-1 investigated using high-resolution magnetic resonance imaging in healthy volunteers. J Cereb Blood Flow Metab 2020; 40:1685-1694. [PMID: 31500524 PMCID: PMC7370364 DOI: 10.1177/0271678x19874295] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Endothelin-1 (ET-1) is a highly potent vasoconstrictor peptide released from vascular endothelium. ET-1 plays a major role in cerebrovascular disorders and likely worsens the outcome of acute ischaemic stroke and aneurismal subarachnoid haemorrhage through vasoconstriction and cerebral blood flow (CBF) reduction. Disorders that increase the risk of stroke, including hypertension, diabetes mellitus, and acute myocardial infarction, are associated with increased plasma levels of ET-1. The in vivo human cerebrovascular effects of systemic ET-1 infusion have not previously been investigated. In a two-way crossover, randomized, double-blind design, we used advanced 3 tesla MRI methods to investigate the effects of high-dose intravenous ET-1 on intra- and extracranial artery circumferences, global and regional CBF, and cerebral metabolic rate of oxygen (CMRO2) in 14 healthy volunteers. Following ET-1 infusion, we observed a 14% increase of mean arterial blood pressure, a 5% decrease of middle cerebral artery (MCA) circumference, but no effects on extracerebral arteries and no effects on CBF or CMRO2. Collectively, the findings indicate MCA constriction secondarily to blood pressure increase and not due to a direct vasoconstrictor effect of ET-1. We suggest that, as opposed to ET-1 in the subarachnoid space, intravascular ET-1 does not exert direct cerebrovascular effects in humans.
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Affiliation(s)
- Anders Hougaard
- Department of Neurology, Danish Headache Center, Rigshospitalet Glostrup, Glostrup, Denmark
| | - Samaira Younis
- Department of Neurology, Danish Headache Center, Rigshospitalet Glostrup, Glostrup, Denmark
| | - Afrim Iljazi
- Department of Neurology, Danish Headache Center, Rigshospitalet Glostrup, Glostrup, Denmark
| | - Kristian A Haanes
- Department of Clinical Experimental Research, Rigshospitalet Glostrup, Glostrup, Denmark
| | - Ulrich Lindberg
- Department of Clinical Physiology, Functional Imaging Unit, Nuclear Medicine and PET, Rigshospitalet Glostrup, Glostrup, Denmark
| | - Mark B Vestergaard
- Department of Clinical Physiology, Functional Imaging Unit, Nuclear Medicine and PET, Rigshospitalet Glostrup, Glostrup, Denmark
| | - Faisal M Amin
- Department of Neurology, Danish Headache Center, Rigshospitalet Glostrup, Glostrup, Denmark
| | - Kazutaka Sugimoto
- Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, USA.,Department of Neurosurgery, Yamaguchi University School of Medicine, Yamaguchi, Japan
| | - Lars S Kruse
- Department of Clinical Experimental Research, Rigshospitalet Glostrup, Glostrup, Denmark.,Department of Biochemistry, Rigshospitalet Glostrup, Glostrup, Denmark
| | - Cenk Ayata
- Stroke Service, Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Charlestown, USA
| | - Messoud Ashina
- Department of Neurology, Danish Headache Center, Rigshospitalet Glostrup, Glostrup, Denmark
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13
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Carvalho LB, Kramer S, Borschmann K, Chambers B, Thijs V, Bernhardt J. Cerebral haemodynamics with head position changes post-ischaemic stroke: A systematic review and meta-analysis. J Cereb Blood Flow Metab 2020; 40:271678X20922457. [PMID: 32404023 PMCID: PMC7786838 DOI: 10.1177/0271678x20922457] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/20/2019] [Revised: 02/20/2020] [Accepted: 04/02/2020] [Indexed: 01/01/2023]
Abstract
The effects of upright postures on the cerebral circulation early post-ischaemic stroke are not fully understood. We conducted a systematic review and meta-analysis to investigate the effects of head positioning on cerebral haemodynamics assessed by imaging methods post-ischaemic stroke. Of the 21 studies included (n = 529), 15 used transcranial Doppler. Others used near-infrared, diffuse correlation spectroscopy and nuclear medicine modalities. Most tested head positions between 0° and 45°. Seventeen studies reported changes in CBF parameters (increase at lying-flat or decrease at more upright) in the ischaemic hemisphere with position change. However, great variability was found and risk of bias was high in many studies. Pooled data of two studies ≤24 h (n = 28) showed a mean increase in cerebral blood flow (CBF) velocity of 8.5 cm/s in the ischaemic middle cerebral artery (95%CI,-2.2-19.3) from 30° to 0°. The increase found ≤48 h (n = 50) was of 2.3 cm/s (95%CI,-4.6-9.2), while ≤7 days (n = 38) was of 8.4 cm/s (95%CI, 1.8-15). Few very early studies (≤2 days) tested head positions greater than 30° and were unable to provide information about the response of acute stroke patients to upright postures (sitting, standing). These postures are part of current clinical practice and knowledge on their effects on cerebral haemodynamics is required.
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Affiliation(s)
- Lilian B Carvalho
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Heidelberg, Australia
- NHMRC Centre for Research Excellence in Stroke Rehabilitation and Brain Recovery, Heidelberg, Australia
| | - Sharon Kramer
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Heidelberg, Australia
- NHMRC Centre for Research Excellence in Stroke Rehabilitation and Brain Recovery, Heidelberg, Australia
| | - Karen Borschmann
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Heidelberg, Australia
- NHMRC Centre for Research Excellence in Stroke Rehabilitation and Brain Recovery, Heidelberg, Australia
- St Vincent’s Hospital, Melbourne, Australia
| | - Brian Chambers
- Department of Neurology, Austin Health, Heidelberg, Australia
- Department of Medicine, University of Melbourne, Victoria, Australia
| | - Vincent Thijs
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Heidelberg, Australia
- Department of Neurology, Austin Health, Heidelberg, Australia
| | - Julie Bernhardt
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Heidelberg, Australia
- NHMRC Centre for Research Excellence in Stroke Rehabilitation and Brain Recovery, Heidelberg, Australia
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14
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Zhang W, Xie S, Han D, Huang J, Ou-Yang C, Lu J. Effects of relative low minute ventilation on cerebral haemodynamics in infants undergoing ventricular septal defect repair. Cardiol Young 2020; 30:205-12. [PMID: 31937383 DOI: 10.1017/S1047951119003135] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
BACKGROUND Ventilation-associated changes in blood carbon dioxide levels are associated with various physiological changes in infants undergoing surgery. Studies on the effects of mechanical ventilation on cerebral haemodynamics especially for infants with CHD are scarce. AIM This study was done to compare the changes in regional cerebral oxygen saturation and cerebral blood flow velocity when the end-tidal carbon dioxide partial pressure changed during different minute ventilation settings in infants undergoing ventricular septal defect repair. METHODS A total of 67 patients less than 1 year old with ventricular septal defect were enrolled, and 65 patients (age: 6.7 ± 3.4 months, weight: 6.4 ± 1.5 kg) were studied. After anaesthesia induction and endotracheal intubation, the same mechanical ventilation mode (The fraction of inspired oxygen was 50%, and the inspiratory-to-expiratory ratio was 1:1.5.) was adopted. The end-tidal carbon dioxide partial pressure of 30 mmHg (T1), 35 mmHg (T2), 40 mmHg (T3), or 45 mmHg (T4) were obtained, respectively, by adjusting tidal volume and respiratory rate. Minute ventilation per kilogram was calculated by the formula: minute ventilation per kilogram = tidal volume * respiratory rate/kg. Regional cerebral oxygen saturation was monitored by real-time near-infrared spectroscopy. Cerebral blood flow velocity (systolic flow velocity, end-diastolic flow velocity, and mean flow velocity), pulsatility index, and resistance index were measured intermittently by transcranial Doppler. Systolic pressure, diastolic pressure, stroke volume index, and cardiac index were recorded using the pressure recording analytical method. RESULTS As the end-tidal carbon dioxide partial pressure increased from 30 to 45 mmHg, regional cerebral oxygen saturation increased significantly from 69 ± 5% to 79 ± 4% (p < 0.001). Cerebral blood flow velocity (systolic flow velocity, end-diastolic flow velocity, and mean flow velocity) increased linearly, while pulsatility index and resistance index decreased linearly from T1 (systolic flow velocity, 84 ± 19 cm/second; end-diastolic flow velocity, 14 ± 4 cm/second; mean flow velocity, 36 ± 10 cm/second; pulsatility index, 2.13 ± 0.59; resistance index, 0.84 ± 0.12) to T4 (systolic flow velocity, 113 ± 22 cm/second; end-diastolic flow velocity, 31 ± 6 cm/second; mean flow velocity, 58 ± 11 cm/second; pulsatility index, 1.44 ± 0.34; resistance index, 0.72 ± 0.07) (p < 0.001). There were significant differences in changes of systolic flow velocity, end-diastolic flow velocity, mean flow velocity, pulsatility index, and resistance index as the end-tidal carbon dioxide partial pressure increased from 30 to 45 mmHg between subgroups of infants ≤6 and infants >6 months, while the changes of regional cerebral oxygen saturation between subgroups were not statistically different. Regional cerebral oxygen saturation and cerebral blood flow velocity (systolic flow velocity, end-diastolic flow velocity, and mean flow velocity) were negatively correlated with minute ventilation per kilogram (r = -0.538, r = -0.379, r = -0.504, r = -0.505, p < 0.001). Pulsatility index and resistance index were positively related to minute ventilation per kilogram (r = 0.464, r = 0.439, p < 0.001). The diastolic pressure was significantly reduced from T1 (41 ± 7 mmHg) to T4 (37 ± 6 mmHg) (p < 0.001). There were no significant differences in systolic pressure, stroke volume index, and cardiac index with the change of end-tidal carbon dioxide partial pressure from T1 to T4 (p = 0.063, p = 0.382, p = 0.165, p > 0.05). CONCLUSION A relative low minute ventilation strategy increases regional cerebral oxygen saturation and cerebral blood flow, which may improve cerebral oxygenation and brain perfusion in infants undergoing ventricular septal defect repair.
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15
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Peng B, Dai J, Li J, Liang C, Liang X. Ictal cerebral haemodynamic characteristics during typical absence seizures, compared to focal seizures with brief alteration of awareness. Epileptic Disord 2019; 21:244-51. [PMID: 31225802 DOI: 10.1684/epd.2019.1067] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
To investigate ictal cerebral haemodynamic characteristics during spontaneous typical absence seizures (TAS) and hyperventilation-evoked absence seizures in paediatric patients, relative to brief complex partial seizures (BCPS). All children diagnosed with seizures using real-time transcranial doppler ultrasonography (TCD) and sleep-deprived video-EEG (vEEG) from 2015 to 2017 in our hospital were included. The seizures were diagnosed based on the video and EEG findings. Mean cerebral blood flow velocity (CBFVm) of the unilateral middle cerebral artery was measured using TCD. TCD and vEEG data were integrated for a synchronous assessment of CBFVm changes and epileptic status. Baseline and peak CBFVm for TAS and BCPS were compared by T-test. Six children (two boys and four girls) with TAS and two girls with BCPS were enrolled. A total of 15 spontaneous TAS, 14 hyperventilation-evoked absence seizures, and six BCPS were recorded using real-time TCD-vEEG monitoring. During spontaneous TAS, whether awake or asleep, the CBFVm decreased by 20-40% compared to baseline. During hyperventilation-evoked absence seizures and BCPS, the CBFVm increased by 50-150% and 20-30% over baseline levels, respectively. The haemodynamic characteristics during TAS and BCPS are distinct, and thus our results may provide a new method to diagnose typical absence seizures using dynamic CBFVm curves. Ictal cerebral haemodynamic characteristics during spontaneous typical absence seizures and hyperventilation-evoked absence seizures may reflect different pathophysiological mechanisms and networks compared with BCPS.
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16
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Beishon L, Evley R, Panerai RB, Subramaniam H, Mukaetova-Ladinska E, Robinson T, Haunton V. Effects of brain training on brain blood flow (The Cognition and Flow Study-CogFlowS): protocol for a feasibility randomised controlled trial of cognitive training in dementia. BMJ Open 2019; 9:e027817. [PMID: 31122994 PMCID: PMC6538045 DOI: 10.1136/bmjopen-2018-027817] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Revised: 04/11/2019] [Accepted: 04/29/2019] [Indexed: 12/13/2022] Open
Abstract
INTRODUCTION Cognitive training is an emerging non-pharmacological treatment to improve cognitive and physical function in mild cognitive impairment (MCI) and early Alzheimer's disease (AD). Abnormal brain blood flow is a key process in the development of cognitive decline. However, no studies have explored the effects of cognitive training on brain blood flow in dementia. The primary aim of this study is to assess the feasibility for a large-scale, randomised controlled trial of cognitive training in healthy older adults (HC), MCI and early AD. METHODS AND ANALYSIS This study will recruit 60 participants, in three subgroups of 20 (MCI, HC, AD), from primary, secondary and community services. Participants will be randomised to a 12-week computerised cognitive training programme (five × 30 min sessions per week), or waiting-list control. Participants will undergo baseline and follow-up assessments of: mood, cognition, quality of life and activities of daily living. Cerebral blood flow will be measured at rest and during task activation (pretraining and post-training) by bilateral transcranial Doppler ultrasonography, alongside heart rate (3-lead ECG), end-tidal CO2 (capnography) and beat-to-beat blood pressure (Finometer). Participants will be offered to join a focus group or semistructured interview to explore barriers and facilitators to cognitive training in patients with dementia. Qualitative data will be analysed using framework analysis, and data will be integrated using mixed methods matrices. ETHICS AND DISSEMINATION Bradford Leeds Research Ethics committee awarded a favourable opinion (18/YH/0396). Results of the study will be published in peer-reviewed journals, and presented at national and international conferences on ageing and dementia. TRIALS REGISTRATION NUMBER NCT03656107; Pre-results.
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Affiliation(s)
- Lucy Beishon
- Cardiovascular Sciences, University of Leicester College of Medicine Biological Sciences and Psychology, Leicester, UK
| | - Rachel Evley
- Division of Clinical Neuroscience, University of Nottingham, Nottingham, UK
| | - Ronney B Panerai
- Cardiovascular Sciences, University of Leicester College of Medicine Biological Sciences and Psychology, Leicester, UK
- NIHR Leicester Biomedical Research Centre, British Heart Foundation Cardiovascular Research Centre, University of Leicester, Leicester, UK
| | - Hari Subramaniam
- The Evington Centre, Leicestershire Partnership NHSTrust, Leicester, UK
| | | | - Thompson Robinson
- Cardiovascular Sciences, University of Leicester College of Medicine Biological Sciences and Psychology, Leicester, UK
- NIHR Leicester Biomedical Research Centre, British Heart Foundation Cardiovascular Research Centre, University of Leicester, Leicester, UK
| | - Victoria Haunton
- Cardiovascular Sciences, University of Leicester College of Medicine Biological Sciences and Psychology, Leicester, UK
- NIHR Leicester Biomedical Research Centre, British Heart Foundation Cardiovascular Research Centre, University of Leicester, Leicester, UK
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17
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Abstract
With the publication in 2015 of the consensus statement by the perfusion study group of the International Society for Magnetic Resonance in Medicine (ISMRM) and the EU-COST action 'ASL in dementia' on the implementation of arterial spin labelling MRI (ASL) in a clinical setting, the development of ASL can be considered to have become mature and ready for clinical prime-time. In this review article new developments and remaining issues will be discussed, especially focusing on quantification of ASL as well as on new technological developments of ASL for perfusion imaging and flow territory mapping. Uncertainty of the achieved labelling efficiency in pseudo-continuous ASL (pCASL) as well as the presence of arterial transit time artefacts, can be considered the main remaining challenges for the use of quantitative cerebral blood flow (CBF) values. New developments in ASL centre around time-efficient acquisition of dynamic ASL-images by means of time-encoded pCASL and diversification of information content, for example by combined 4D-angiography with perfusion imaging. Current vessel-encoded and super-selective pCASL-methodology have developed into easily applied flow-territory mapping methods providing relevant clinical information with highly similar information content as digital subtraction angiography (DSA), the current clinical standard. Both approaches seem therefore to be ready for clinical use.
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Affiliation(s)
- Matthias Jp van Osch
- 1 Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands.,2 Leiden Institute of Brain and Cognition, Leiden University, Leiden, The Netherlands
| | - Wouter M Teeuwisse
- 1 Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands.,2 Leiden Institute of Brain and Cognition, Leiden University, Leiden, The Netherlands
| | - Zhensen Chen
- 3 Department of Biomedical Engineering, Tsinghua University, Beijing, China
| | - Yuriko Suzuki
- 1 Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Michael Helle
- 4 Philips GmbH Innovative Technologies, Research Laboratories, Hamburg, Germany
| | - Sophie Schmid
- 1 Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands.,2 Leiden Institute of Brain and Cognition, Leiden University, Leiden, The Netherlands
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18
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Kawadler JM, Hales PW, Barker S, Cox TCS, Kirkham FJ, Clark CA. Cerebral perfusion characteristics show differences in younger versus older children with sickle cell anaemia: Results from a multiple-inflow-time arterial spin labelling study. NMR Biomed 2018; 31:e3915. [PMID: 29601112 DOI: 10.1002/nbm.3915] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Revised: 02/07/2018] [Accepted: 02/11/2018] [Indexed: 06/08/2023]
Abstract
Sickle cell anaemia (SCA) is associated with chronic anaemia and oxygen desaturation, which elevate cerebral blood flow (CBF) and increase the risk of neurocognitive complications. Arterial spin labelling (ASL) provides a methodology for measuring CBF non-invasively; however, ASL techniques using only a single inflow time are not sufficient to fully characterize abnormal haemodynamic behaviour in SCA. This study investigated haemodynamic parameters from a multi-inflow-time ASL acquisition in younger (8-12 years) and older (13-18 years) children with SCA with and without silent cerebral infarction (SCI+/-) (n = 20 and 19 respectively, 6 and 4 SCI+ respectively) and healthy controls (n = 9 and 7 respectively). Compared with controls, CBF was elevated globally in both groups of patients. In the younger SCA patients, blood oxygen content was negatively correlated with CBF in the middle and posterior cerebral artery territories and significantly positively correlated with bolus arrival time (BAT) in the anterior and middle cerebral artery territories. In older children, SCA patients had significantly shorter BAT than healthy controls and there was a significant negative correlation between CBF and oxygen content only in the territory of the posterior cerebral artery, with a trend for a correlation in the anterior cerebral artery but no relationship for the middle cerebral artery territory. In the younger group, SCI+ patients had significantly higher CBF in the posterior cerebral artery territory (SCI+ mean = 92.78 ml/100 g/min; SCI- mean = 72.71 ml/100 g/min; F = 4.28, p = 0.04), but this no longer reached significance when two children with abnormal transcranial Doppler and one with haemoglobin SC disease were excluded, and there were no significant differences between patients with and without SCI in the older children. With age, there appears to be increasing disparity between patients and controls in terms of the relationship between CBF and oxygen content in the anterior circulation, potentially predicting the risk of acute and chronic compromise of brain tissue.
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Affiliation(s)
- Jamie M Kawadler
- Developmental Neurosciences, UCL Great Ormond Street Institute of Child Health, London, UK
| | - Patrick W Hales
- Developmental Neurosciences, UCL Great Ormond Street Institute of Child Health, London, UK
| | - Simon Barker
- Wessex Neurological Centre and Child Health, University Hospital Southampton, Southampton, UK
| | - Timothy C S Cox
- Department of Radiology, Great Ormond Street Hospital, London, UK
| | - Fenella J Kirkham
- Developmental Neurosciences, UCL Great Ormond Street Institute of Child Health, London, UK
- Wessex Neurological Centre and Child Health, University Hospital Southampton, Southampton, UK
- Clinical and Experimental Sciences, University of Southampton, Southampton, UK
| | - Chris A Clark
- Developmental Neurosciences, UCL Great Ormond Street Institute of Child Health, London, UK
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Curtelin D, Morales-Alamo D, Torres-Peralta R, Rasmussen P, Martin-Rincon M, Perez-Valera M, Siebenmann C, Pérez-Suárez I, Cherouveim E, Sheel AW, Lundby C, Calbet JA. Cerebral blood flow, frontal lobe oxygenation and intra-arterial blood pressure during sprint exercise in normoxia and severe acute hypoxia in humans. J Cereb Blood Flow Metab 2018; 38:136-150. [PMID: 28186430 PMCID: PMC5757439 DOI: 10.1177/0271678x17691986] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Cerebral blood flow (CBF) is regulated to secure brain O2 delivery while simultaneously avoiding hyperperfusion; however, both requisites may conflict during sprint exercise. To determine whether brain O2 delivery or CBF is prioritized, young men performed sprint exercise in normoxia and hypoxia (PIO2 = 73 mmHg). During the sprints, cardiac output increased to ∼22 L min-1, mean arterial pressure to ∼131 mmHg and peak systolic blood pressure ranged between 200 and 304 mmHg. Middle-cerebral artery velocity (MCAv) increased to peak values (∼16%) after 7.5 s and decreased to pre-exercise values towards the end of the sprint. When the sprints in normoxia were preceded by a reduced PETCO2, CBF and frontal lobe oxygenation decreased in parallel ( r = 0.93, P < 0.01). In hypoxia, MCAv was increased by 25%, due to a 26% greater vascular conductance, despite 4-6 mmHg lower PaCO2 in hypoxia than normoxia. This vasodilation fully accounted for the 22 % lower CaO2 in hypoxia, leading to a similar brain O2 delivery during the sprints regardless of PIO2. In conclusion, when a conflict exists between preserving brain O2 delivery or restraining CBF to avoid potential damage by an elevated perfusion pressure, the priority is given to brain O2 delivery.
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Affiliation(s)
- David Curtelin
- 1 Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Canary Islands, Spain.,2 Emergency Medicine Department, Insular Universitary Hospital of Gran Canaria, Las Palmas de Gran Canaria, Spain
| | - David Morales-Alamo
- 1 Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Canary Islands, Spain.,3 Department of Physical Education, University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Spain
| | - Rafael Torres-Peralta
- 1 Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Canary Islands, Spain.,3 Department of Physical Education, University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Spain
| | - Peter Rasmussen
- 4 Center for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zürich, Switzerland
| | - Marcos Martin-Rincon
- 1 Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Canary Islands, Spain.,3 Department of Physical Education, University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Spain
| | - Mario Perez-Valera
- 1 Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Canary Islands, Spain.,3 Department of Physical Education, University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Spain
| | - Christoph Siebenmann
- 4 Center for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zürich, Switzerland
| | - Ismael Pérez-Suárez
- 1 Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Canary Islands, Spain.,3 Department of Physical Education, University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Spain
| | - Evgenia Cherouveim
- 5 Department of Physical Education and Sport Sciences, National and Kapodistrian University of Athens, Athens, Greece
| | - A William Sheel
- 6 School of Kinesiology, University of British Columbia, Vancouver, Canada
| | - Carsten Lundby
- 4 Center for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zürich, Switzerland
| | - José Al Calbet
- 1 Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Canary Islands, Spain.,3 Department of Physical Education, University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Spain
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20
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Donnelly J, Czosnyka M, Adams H, Robba C, Steiner LA, Cardim D, Cabella B, Liu X, Ercole A, Hutchinson PJ, Menon DK, Aries MJH, Smielewski P. Individualizing Thresholds of Cerebral Perfusion Pressure Using Estimated Limits of Autoregulation. Crit Care Med 2017; 45:1464-1471. [PMID: 28816837 PMCID: PMC5595234 DOI: 10.1097/ccm.0000000000002575] [Citation(s) in RCA: 98] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
OBJECTIVES In severe traumatic brain injury, cerebral perfusion pressure management based on cerebrovascular pressure reactivity index has the potential to provide a personalized treatment target to improve patient outcomes. So far, the methods have focused on identifying "one" autoregulation-guided cerebral perfusion pressure target-called "cerebral perfusion pressure optimal". We investigated whether a cerebral perfusion pressure autoregulation range-which uses a continuous estimation of the "lower" and "upper" cerebral perfusion pressure limits of cerebrovascular pressure autoregulation (assessed with pressure reactivity index)-has prognostic value. DESIGN Single-center retrospective analysis of prospectively collected data. SETTING The neurocritical care unit at a tertiary academic medical center. PATIENTS Data from 729 severe traumatic brain injury patients admitted between 1996 and 2016 were used. Treatment was guided by controlling intracranial pressure and cerebral perfusion pressure according to a local protocol. INTERVENTIONS None. METHODS AND MAIN RESULTS Cerebral perfusion pressure-pressure reactivity index curves were fitted automatically using a previously published curve-fitting heuristic from the relationship between pressure reactivity index and cerebral perfusion pressure. The cerebral perfusion pressure values at which this "U-shaped curve" crossed the fixed threshold from intact to impaired pressure reactivity (pressure reactivity index = 0.3) were denoted automatically the "lower" and "upper" cerebral perfusion pressure limits of reactivity, respectively. The percentage of time with cerebral perfusion pressure below (%cerebral perfusion pressure < lower limit of reactivity), above (%cerebral perfusion pressure > upper limit of reactivity), or within these reactivity limits (%cerebral perfusion pressure within limits of reactivity) was calculated for each patient and compared across dichotomized Glasgow Outcome Scores. After adjusting for age, initial Glasgow Coma Scale, and mean intracranial pressure, percentage of time with cerebral perfusion pressure less than lower limit of reactivity was associated with unfavorable outcome (odds ratio %cerebral perfusion pressure < lower limit of reactivity, 1.04; 95% CI, 1.02-1.06; p < 0.001) and mortality (odds ratio, 1.06; 95% CI, 1.04-1.08; p < 0.001). CONCLUSIONS Individualized autoregulation-guided cerebral perfusion pressure management may be a plausible alternative to fixed cerebral perfusion pressure threshold management in severe traumatic brain injury patients. Prospective randomized research will help define which autoregulation-guided method is beneficial, safe, and most practical.
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Affiliation(s)
- Joseph Donnelly
- Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, Cambridge Biomedical Campus, University of Cambridge, Cambridge, UK
| | - Marek Czosnyka
- Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, Cambridge Biomedical Campus, University of Cambridge, Cambridge, UK
- Institute of Electronic Systems, Warsaw University of Technology, Poland
| | - Hadie Adams
- Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, Cambridge Biomedical Campus, University of Cambridge, Cambridge, UK
| | - Chiara Robba
- Division of Anaesthesia, Department of Medicine, Addenbrooke’s Hospital, University of Cambridge, Cambridge, UK
- Department of Neuroscience, University of Genoa, Italy
| | - Luzius A Steiner
- Department for Anesthesia, Surgical Intensive Care, Prehospital Emergency Medicine and Pain Therapy, University Hospital Basel, University of Basel Switzerland
| | - Danilo Cardim
- Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, Cambridge Biomedical Campus, University of Cambridge, Cambridge, UK
| | - Brenno Cabella
- Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, Cambridge Biomedical Campus, University of Cambridge, Cambridge, UK
| | - Xiuyun Liu
- Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, Cambridge Biomedical Campus, University of Cambridge, Cambridge, UK
| | - Ari Ercole
- Division of Anaesthesia, Department of Medicine, Addenbrooke’s Hospital, University of Cambridge, Cambridge, UK
| | - Peter J Hutchinson
- Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke’s Hospital, University of Cambridge, Cambridge, UK
| | - David K Menon
- Division of Anaesthesia, Department of Medicine, Addenbrooke’s Hospital, University of Cambridge, Cambridge, UK
| | - Marcel JH Aries
- Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, Cambridge Biomedical Campus, University of Cambridge, Cambridge, UK
- Department of Intensive Care, University of Maastricht, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Peter Smielewski
- Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, Cambridge Biomedical Campus, University of Cambridge, Cambridge, UK
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21
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Sánchez-Porras R, Santos E, Schöll M, Kunzmann K, Stock C, Silos H, Unterberg AW, Sakowitz OW. Ketamine modulation of the haemodynamic response to spreading depolarization in the gyrencephalic swine brain. J Cereb Blood Flow Metab 2017; 37:1720-1734. [PMID: 27126324 PMCID: PMC5435283 DOI: 10.1177/0271678x16646586] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Revised: 03/17/2016] [Accepted: 03/20/2016] [Indexed: 11/16/2022]
Abstract
Spreading depolarization (SD) generates significant alterations in cerebral haemodynamics, which can have detrimental consequences on brain function and integrity. Ketamine has shown an important capacity to modulate SD; however, its impact on SD haemodynamic response is incompletely understood. We investigated the effect of two therapeutic ketamine dosages, a low-dose of 2 mg/kg/h and a high-dose of 4 mg/kg/h, on the haemodynamic response to SD in the gyrencephalic swine brain. Cerebral blood volume, pial arterial diameter and cerebral blood flow were assessed through intrinsic optical signal imaging and laser-Doppler flowmetry. Our findings indicate that frequent SDs caused a persistent increase in the baseline pial arterial diameter, which can lead to a diminished capacity to further dilate. Ketamine infused at a low-dose reduced the hyperemic/vasodilative response to SD; however, it did not alter the subsequent oligemic/vasoconstrictive response. This low-dose did not prevent the baseline diameter increase and the diminished dilative capacity. Only infusion of ketamine at a high-dose suppressed SD and the coupled haemodynamic response. Therefore, the haemodynamic response to SD can be modulated by continuous infusion of ketamine. However, its use in pathological models needs to be explored to corroborate its possible clinical benefit.
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Affiliation(s)
| | - Edgar Santos
- Department of Neurosurgery, Heidelberg University Hospital, Heidelberg, Germany
| | - Michael Schöll
- Department of Neurosurgery, Heidelberg University Hospital, Heidelberg, Germany
- Institute of Medical Biometry and Informatics, University of Heidelberg, Heidelberg, Germany
| | - Kevin Kunzmann
- Institute of Medical Biometry and Informatics, University of Heidelberg, Heidelberg, Germany
| | - Christian Stock
- Institute of Medical Biometry and Informatics, University of Heidelberg, Heidelberg, Germany
| | - Humberto Silos
- Department of Neurosurgery, Heidelberg University Hospital, Heidelberg, Germany
| | - Andreas W Unterberg
- Department of Neurosurgery, Heidelberg University Hospital, Heidelberg, Germany
| | - Oliver W Sakowitz
- Department of Neurosurgery, Heidelberg University Hospital, Heidelberg, Germany
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22
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Donnelly J, Czosnyka M, Harland S, Varsos GV, Cardim D, Robba C, Liu X, Ainslie PN, Smielewski P. Cerebral haemodynamics during experimental intracranial hypertension. J Cereb Blood Flow Metab 2017; 37:694-705. [PMID: 26994043 PMCID: PMC5381462 DOI: 10.1177/0271678x16639060] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Intracranial hypertension is a common final pathway in many acute neurological conditions. However, the cerebral haemodynamic response to acute intracranial hypertension is poorly understood. We assessed cerebral haemodynamics (arterial blood pressure, intracranial pressure, laser Doppler flowmetry, basilar artery Doppler flow velocity, and vascular wall tension) in 27 basilar artery-dependent rabbits during experimental (artificial CSF infusion) intracranial hypertension. From baseline (∼9 mmHg; SE 1.5) to moderate intracranial pressure (∼41 mmHg; SE 2.2), mean flow velocity remained unchanged (47 to 45 cm/s; p = 0.38), arterial blood pressure increased (88.8 to 94.2 mmHg; p < 0.01), whereas laser Doppler flowmetry and wall tension decreased (laser Doppler flowmetry 100 to 39.1% p < 0.001; wall tension 19.3 to 9.8 mmHg, p < 0.001). From moderate to high intracranial pressure (∼75 mmHg; SE 3.7), both mean flow velocity and laser Doppler flowmetry decreased (45 to 31.3 cm/s p < 0.001, laser Doppler flowmetry 39.1 to 13.3%, p < 0.001), arterial blood pressure increased still further (94.2 to 114.5 mmHg; p < 0.001), while wall tension was unchanged (9.7 to 9.6 mmHg; p = 0.35).This animal model of acute intracranial hypertension demonstrated two intracranial pressure-dependent cerebroprotective mechanisms: with moderate increases in intracranial pressure, wall tension decreased, and arterial blood pressure increased, while with severe increases in intracranial pressure, an arterial blood pressure increase predominated. Clinical monitoring of such phenomena could help individualise the management of neurocritical patients.
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Affiliation(s)
- Joseph Donnelly
- 1 Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, Cambridge Biomedical Campus, University of Cambridge, Cambridge, UK
| | - Marek Czosnyka
- 1 Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, Cambridge Biomedical Campus, University of Cambridge, Cambridge, UK.,2 Institute of Electronic Systems, Warsaw University of Technology, Warsaw, Poland
| | | | - Georgios V Varsos
- 1 Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, Cambridge Biomedical Campus, University of Cambridge, Cambridge, UK
| | - Danilo Cardim
- 1 Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, Cambridge Biomedical Campus, University of Cambridge, Cambridge, UK
| | - Chiara Robba
- 1 Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, Cambridge Biomedical Campus, University of Cambridge, Cambridge, UK
| | - Xiuyun Liu
- 1 Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, Cambridge Biomedical Campus, University of Cambridge, Cambridge, UK
| | - Philip N Ainslie
- 4 Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Okanagan, Kelowna, British Columbia, Canada
| | - Peter Smielewski
- 1 Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, Cambridge Biomedical Campus, University of Cambridge, Cambridge, UK
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23
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Roth C, Stitz H, Roth C, Ferbert A, Deinsberger W, Pahl R, Engel H, Kleffmann J. Craniocervical manual lymphatic drainage and its impact on intracranial pressure - a pilot study. Eur J Neurol 2016; 23:1441-6. [PMID: 27238738 DOI: 10.1111/ene.13055] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2016] [Accepted: 04/21/2016] [Indexed: 11/30/2022]
Abstract
BACKGROUND AND PURPOSE Theoretical considerations and the results of animal studies indicate that manual lymphatic drainage (MLD) might have an impact on intracranial pressure (ICP). There is a lack of clinically qualitative investigations on patients with severe cerebral diseases. METHODS Between April 2013 and January 2015 a prospective observational study was performed on patients who were undergoing intracranial pressure measurement and treatment with MLD. ICP, cerebral perfusion pressure, mean arterial pressure (MAP), heart rate and oxygen saturation were recorded continuously 15 min before the procedure, during MLD (22 min) and for 15 min after the procedure. For analysis the data treatment units were divided into two groups: patients with a mean baseline ICP <15 mmHg (group 1) and patients with a mean ICP ≥15 mmHg before MLD (group 2). RESULTS A total of 133 treatment units (61 patients) were analysed (group 1 n = 99; group 2 n = 34). The mean baseline ICP was 10.4 mmHg overall, and 8.3 mmHg and 18.6 mmHg respectively in group 1 and group 2; ICP significantly decreased during therapy with MLD and this persisted during the follow-up period in group 2. MAP did not show any significant differences between the different periods. CONCLUSIONS Our data showed a significant reduction of ICP during therapy with craniocervical MLD in patients with severe cerebral diseases.
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Affiliation(s)
- C Roth
- Department of Neurology, Klinikum Kassel, Kassel, Germany
| | - H Stitz
- Department of Physiotherapy, Klinikum Kassel, Kassel, Germany
| | - C Roth
- Department of Physiotherapy, Klinikum Kassel, Kassel, Germany
| | - A Ferbert
- Department of Neurology, Klinikum Kassel, Kassel, Germany
| | - W Deinsberger
- Department of Neurosurgery, Klinikum Kassel, Kassel, Germany
| | - R Pahl
- Institute of Medical Biometry and Epidemiology (IMBE), Philipps University Marburg, Marburg, Germany
| | - H Engel
- Department of Hand, Plastic and Reconstructive Surgery, Klinikum Kassel, Kassel, Germany
| | - J Kleffmann
- Department of Neurosurgery, Klinikum Kassel, Kassel, Germany
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24
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Jordan LC, Gindville MC, Scott AO, Juttukonda MR, Strother MK, Kassim AA, Chen SC, Lu H, Pruthi S, Shyr Y, Donahue MJ. Non-invasive imaging of oxygen extraction fraction in adults with sickle cell anaemia. Brain 2016; 139:738-50. [PMID: 26823369 DOI: 10.1093/brain/awv397] [Citation(s) in RCA: 86] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Accepted: 11/30/2015] [Indexed: 11/12/2022] Open
Abstract
Sickle cell anaemia is a monogenetic disorder with a high incidence of stroke. While stroke screening procedures exist for children with sickle cell anaemia, no accepted screening procedures exist for assessing stroke risk in adults. The purpose of this study is to use novel magnetic resonance imaging methods to evaluate physiological relationships between oxygen extraction fraction, cerebral blood flow, and clinical markers of cerebrovascular impairment in adults with sickle cell anaemia. The specific goal is to determine to what extent elevated oxygen extraction fraction may be uniquely present in patients with higher levels of clinical impairment and therefore may represent a candidate biomarker of stroke risk. Neurological evaluation, structural imaging, and the non-invasive T2-relaxation-under-spin-tagging magnetic resonance imaging method were applied in sickle cell anaemia (n = 34) and healthy race-matched control (n = 11) volunteers without sickle cell trait to assess whole-brain oxygen extraction fraction, cerebral blood flow, degree of vasculopathy, severity of anaemia, and presence of prior infarct; findings were interpreted in the context of physiological models. Cerebral blood flow and oxygen extraction fraction were elevated (P < 0.05) in participants with sickle cell anaemia (n = 27) not receiving monthly blood transfusions (interquartile range cerebral blood flow = 46.2-56.8 ml/100 g/min; oxygen extraction fraction = 0.39-0.50) relative to controls (interquartile range cerebral blood flow = 40.8-46.3 ml/100 g/min; oxygen extraction fraction = 0.33-0.38). Oxygen extraction fraction (P < 0.0001) but not cerebral blood flow was increased in participants with higher levels of clinical impairment. These data provide support for T2-relaxation-under-spin-tagging being able to quickly and non-invasively detect elevated oxygen extraction fraction in individuals with sickle cell anaemia with higher levels of clinical impairment. Our results support the premise that magnetic resonance imaging-based assessment of elevated oxygen extraction fraction might be a viable screening tool for evaluating stroke risk in adults with sickle cell anaemia.
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Affiliation(s)
- Lori C Jordan
- 1 Department of Pediatrics, Division of Pediatric Neurology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Melissa C Gindville
- 1 Department of Pediatrics, Division of Pediatric Neurology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Allison O Scott
- 2 Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Meher R Juttukonda
- 2 Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Megan K Strother
- 2 Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Adetola A Kassim
- 3 Vanderbilt-Meharry Center of Excellence in Sickle Cell Disease, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Sheau-Chiann Chen
- 4 Center for Quantitative Sciences, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Hanzhang Lu
- 5 Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Sumit Pruthi
- 2 Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Yu Shyr
- 4 Center for Quantitative Sciences, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Manus J Donahue
- 2 Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, USA 6 Department of Psychiatry, Vanderbilt University Medical Center, Nashville, TN, USA 7 Department of Neurology, Vanderbilt University Medical Center, Nashville, TN, USA
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25
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Wright GAK, Sharifi Y, Newman TA, Davies N, Vairappan B, Perry HV, Jalan R. Characterisation of temporal microglia and astrocyte immune responses in bile duct-ligated rat models of cirrhosis. Liver Int 2014; 34:1184-91. [PMID: 24528887 DOI: 10.1111/liv.12481] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/19/2013] [Accepted: 01/31/2014] [Indexed: 12/24/2022]
Abstract
BACKGROUND & AIMS Microglia and astrocyte related pro-inflammatory responses are thought to underpin cerebral sequelae of acute liver failure. Conversely, despite background pro-inflammatory responses in cirrhosis, overt brain swelling and coma associated with acute-on-chronic liver failure, is infrequent unless precipitated (e.g. sepsis). Moreover in other chronic neurodegenerative disorders and sepsis, the brain is protected from recurrent microbial insults by compensatory microglial-associated immune responses. To characterise longitudinal cerebral immune responses in a bile duct-ligated (BDL) rat model of cirrhosis. METHOD Rats underwent BDL or sham operation before sacrifice at either 1-day, 1, 2 and 4 weeks post-surgery. We analysed consciousness, brain water, biochemistry and immunohistochemistry to assess activation of microglia (ED-1, OX6 and Iba-1), astrocytes (Glial fibrillary acidic protein - GFAP), cellular stress (Heat shock protein - Hsp 25) and pro-inflammatory mediator expression (inducible nitric oxide synthase (iNOS), interleukin-1beta (IL-1β) and tumour growth factor-beta (TGF-β)). RESULTS BDL significantly increased ammonia and bilirubin (P < 0.01 respectively). The classical microglial markers OX6, ED1 and Iba-1 and pro-inflammatory IL-1β and iNOS were not significantly increased. However, the alternative microglial marker and regulatory cytokine TGF-β was elevated from day 1 to 4 weeks post-BDL. GFAP expression was significantly increased in corpus callosum in all groups. In BDL rats, Hsp 25 was also increased in the corpus callosum, peaking at 2 weeks. CONCLUSION BDL triggers early alternative, but not classical, microglial activation. There was a correlation between astrocyte activation and cellular stress. These findings indicate early cerebral immune responses, which may be associated with immune tolerance to further challenge.
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Affiliation(s)
- Gavin A K Wright
- Institute of Hepatology, University College London, Royal Free Hospital London, London, UK
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26
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Toksvang LN, Plovsing RR, Petersen MW, Møller K, Berg RMG. Poor agreement between transcranial Doppler and near-infrared spectroscopy-based estimates of cerebral blood flow changes in sepsis. Clin Physiol Funct Imaging 2014; 34:405-9. [PMID: 24750661 DOI: 10.1111/cpf.12120] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2013] [Accepted: 11/25/2013] [Indexed: 11/28/2022]
Abstract
BACKGROUND Continuous monitoring of cerebral blood flow (CBF) may be valuable in critically ill patients with sepsis. In this study, we compared spatially resolved near-infrared spectroscopy (NIRS) to transcranial Doppler ultrasound (TCD)-derived estimates of noradrenaline-associated changes in CBF in such patients. METHODS Mean arterial blood pressure (MAP) was elevated by increasing the noradrenaline infusion rate in eight mechanically ventilated, critically ill patients diagnosed with severe sepsis or septic shock. The associated changes in CBF were assessed by simultaneous ipsilateral NIRS (ScO(2)) and TCD (middle cerebral artery blood flow velocity, MCAv) measurements. RESULTS A total of fifteen simultaneous NIRS- and TCD-derived assessments of noradrenaline-associated changes in CBF were obtained. MAP was increased from 74 (median; interquartile range (IQR), 71-90) to 100 (median; IQR, 93-115) mmHg (P<0·05), which was associated with an increase in MCAv of 14% (median; IQR, 2-22; P<0·05), whereas no changes were observed in ScO(2) ; 1% (median; IQR, [-4]-3; P = 0·96). A Bland-Altman plot was used to compare the two methods and showed a poor agreement between NIRS- and TCD-derived estimates with a relative bias of 14% and limits of agreement of -18% to 45% change in CBF. CONCLUSION Our findings stress that TCD and NIRS cannot be used interchangeably for monitoring changes in cerebral haemodynamics in critically ill patients with sepsis receiving vasopressor treatment with noradrenaline.
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Affiliation(s)
- Linea N Toksvang
- Centre of Inflammation and Metabolism, University Hospital Rigshospitalet, Copenhagen Ø, Denmark
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27
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Perry BG, Schlader ZJ, Raman A, Cochrane DJ, Lucas SJE, Mündel T. Middle cerebral artery blood flow velocity in response to lower body positive pressure. Clin Physiol Funct Imaging 2013; 33:483-8. [PMID: 23701382 DOI: 10.1111/cpf.12046] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2013] [Accepted: 04/09/2013] [Indexed: 11/28/2022]
Abstract
Lower body positive pressure (LBPP) has been used in the treatment of haemorrhagic shock and in offsetting g-force induced fluid shifts. However, the middle cerebral artery blood flow velocity (MCAv) response to supine LBPP is unknown. Fifteen healthy volunteers (mean ± SD: age, 26 ± 5 year; body mass, 79 ± 10 kg; height, 174 ± 9 cm) completed 5 minutes of 20 and 40 mm Hg LBPP, in a randomized order, separated by 5 minutes rest (baseline). Beat-to-beat MCAv and blood pressure, partial pressure of end-tidal carbon dioxide (PET CO2 ) and heart rate were recorded and presented as the change from the preceding baseline. All measures were similar between baseline periods (all P>0·30). Mean arterial pressure (MAP) increased by 7 ± 6 (8 ± 7%) and 13 ± 7 mm Hg (19 ± 11%) from baseline during 20 and 40 mm Hg (P<0·01), respectively. The greater MAP increase at 40 mm Hg (P<0·01 versus 20 mm Hg) was mediated via a greater increase in total peripheral resistance (P<0·01), with heart rate, cardiac output (Model flow) and PET CO2 remaining unchanged (all P>0·05) throughout. MCAv increased from baseline by 3 ± 4 cm s(-1) (5 ± 5%) during 20 mm Hg (P = 0·003), whilst no change (P = 0·18) was observed during 40 mm Hg. Our results indicate a divergent response, in that 20 mm Hg LBPP-induced modest increases in both MCAv and MAP, yet no change in MCAv was observed at the higher LBPP of 40 mm Hg despite a further increase in MAP.
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Affiliation(s)
- Blake G Perry
- School of Sport and Exercise, Massey University, Palmerston North, New Zealand
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28
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Budohoski KP, Zweifel C, Kasprowicz M, Sorrentino E, Diedler J, Brady KM, Smielewski P, Menon DK, Pickard JD, Kirkpatrick PJ, Czosnyka M. What comes first? The dynamics of cerebral oxygenation and blood flow in response to changes in arterial pressure and intracranial pressure after head injury. Br J Anaesth 2012; 108:89-99. [PMID: 22037222 PMCID: PMC3236021 DOI: 10.1093/bja/aer324] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/01/2011] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Brain tissue partial oxygen pressure (Pbt(O(2))) and near-infrared spectroscopy (NIRS) are novel methods to evaluate cerebral oxygenation. We studied the response patterns of Pbt(O(2)), NIRS, and cerebral blood flow velocity (CBFV) to changes in arterial pressure (AP) and intracranial pressure (ICP). METHODS Digital recordings of multimodal brain monitoring from 42 head-injured patients were retrospectively analysed. Response latencies and patterns of Pbt(O(2)), NIRS-derived parameters [tissue oxygenation index (TOI) and total haemoglobin index (THI)], and CBFV reactions to fluctuations of AP and ICP were studied. RESULTS One hundred and twenty-one events were identified. In reaction to alterations of AP, ICP reacted first [4.3 s; inter-quartile range (IQR) -4.9 to 22.0 s, followed by NIRS-derived parameters and CBFV (10.9 s; IQR: -5.9 to 39.6 s, 12.1 s; IQR: -3.0 to 49.1 s, 14.7 s; IQR: -8.8 to 52.3 s for THI, CBFV, and TOI, respectively), with Pbt(O(2)) reacting last (39.6 s; IQR: 16.4 to 66.0 s). The differences in reaction time between NIRS parameters and Pbt(O(2)) were significant (P<0.001). Similarly when reactions to ICP changes were analysed, NIRS parameters preceded Pbt(O(2)) (7.1 s; IQR: -8.8 to 195.0 s, 18.1 s; IQR: -20.6 to 80.7 s, 22.9 s; IQR: 11.0 to 53.0 s for THI, TOI, and Pbt(O(2)), respectively). Two main patterns of responses to AP changes were identified. With preserved cerebrovascular reactivity, TOI and Pbt(O(2)) followed the direction of AP. With impaired cerebrovascular reactivity, TOI and Pbt(O(2)) decreased while AP and ICP increased. In 77% of events, the direction of TOI changes was concordant with Pbt(O(2)). CONCLUSIONS NIRS and transcranial Doppler signals reacted first to AP and ICP changes. The reaction of Pbt(O(2)) is delayed. The results imply that the analysed modalities monitor different stages of cerebral oxygenation.
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Affiliation(s)
- K P Budohoski
- Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Addenbrooke' s Hospital, Hills Road, Cambridge CB2 0QQ, UK.
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