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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: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [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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Lalou AD, Czosnyka M, Placek MM, Smielewski P, Nabbanja E, Czosnyka Z. CSF Dynamics for Shunt Prognostication and Revision in Normal Pressure Hydrocephalus. J Clin Med 2021; 10:jcm10081711. [PMID: 33921142 PMCID: PMC8071572 DOI: 10.3390/jcm10081711] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Revised: 04/09/2021] [Accepted: 04/12/2021] [Indexed: 11/16/2022] Open
Abstract
BACKGROUND Despite the quantitative information derived from testing of the CSF circulation, there is still no consensus on what the best approach could be in defining criteria for shunting and predicting response to CSF diversion in normal pressure hydrocephalus (NPH). OBJECTIVE We aimed to review the lessons learned from assessment of CSF dynamics in our center and summarize our findings to date. We have focused on reporting the objective perspective of CSF dynamics testing, without further inferences to individual patient management. DISCUSSION No single parameter from the CSF infusion study has so far been able to serve as an unquestionable outcome predictor. Resistance to CSF outflow (Rout) is an important biological marker of CSF circulation. It should not, however, be used as a single predictor for improvement after shunting. Testing of CSF dynamics provides information on hydrodynamic properties of the cerebrospinal compartment: the system which is being modified by a shunt. Our experience of nearly 30 years of studying CSF dynamics in patients requiring shunting and/or shunt revision, combined with all the recent progress made in producing evidence on the clinical utility of CSF dynamics, has led to reconsidering the relationship between CSF circulation testing and clinical improvement. CONCLUSIONS Despite many open questions and limitations, testing of CSF dynamics provides unique perspectives for the clinician. We have found value in understanding shunt function and potentially shunt response through shunt testing in vivo. In the absence of infusion tests, further methods that provide a clear description of the pre and post-shunting CSF circulation, and potentially cerebral blood flow, should be developed and adapted to the bed-space.
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Affiliation(s)
- Afroditi Despina Lalou
- Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge CB2 0QQ, UK; (M.C.); (M.M.P.); (P.S.); (E.N.); (Z.C.)
- Correspondence: ; Tel.: +44-774-3567-585
| | - Marek Czosnyka
- Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge CB2 0QQ, UK; (M.C.); (M.M.P.); (P.S.); (E.N.); (Z.C.)
- Institute of Electronic Systems, Faculty of Electronics and Information Sciences, Warsaw University of Technology, 00-661 Warsaw, Poland
| | - Michal M. Placek
- Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge CB2 0QQ, UK; (M.C.); (M.M.P.); (P.S.); (E.N.); (Z.C.)
| | - Peter Smielewski
- Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge CB2 0QQ, UK; (M.C.); (M.M.P.); (P.S.); (E.N.); (Z.C.)
| | - Eva Nabbanja
- Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge CB2 0QQ, UK; (M.C.); (M.M.P.); (P.S.); (E.N.); (Z.C.)
| | - Zofia Czosnyka
- Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge CB2 0QQ, UK; (M.C.); (M.M.P.); (P.S.); (E.N.); (Z.C.)
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Kang CH, Roh J, Yeom JA, Ahn SH, Park MG, Park KP, Baik SK. Asymptomatic Cerebral Vasoconstriction after Carotid Artery Stenting. AJNR Am J Neuroradiol 2020; 41:305-309. [PMID: 31974083 DOI: 10.3174/ajnr.a6385] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2019] [Accepted: 12/01/2019] [Indexed: 11/07/2022]
Abstract
BACKGROUND AND PURPOSE Carotid artery stent placement is widely performed for treatment of carotid stenosis. The purpose of this study is to present our observations on cerebral vasoconstriction in ipsilateral anterior circulation during immediate poststenting angiography in patients with near-total occlusion of the proximal ICA. MATERIALS AND METHODS We retrospectively reviewed patient data from December 2008 to December 2018. There were 28 patients with carotid near-total occlusion. Two neuroradiologists reviewed the final cerebral angiographic finding of carotid artery stent placement to evaluate the presence of vasoconstriction or vasodilation. RESULTS A total of 28 patients with near-total occlusion (mean ± standard deviation age, 69.0 ± 6.5 years; 92.9% male) were analyzed. Ten patients showed vasoconstriction in the treated territory, and 18 patients did not show vasoconstriction after carotid artery stenting. There were no statistically significant differences in comorbidity, frequency of symptomatic lesions, antiplatelet medication, mean procedure time, and initial NIHSS and baseline modified Rankin scale scores between the 2 groups. However, vasoconstriction is more likely to happen in patients with isolated territory from the contralateral anterior and posterior circulation (66.7% in the isolated territory group and 12.5% in the not-isolated territory group; P < .05). No headache or neurologic deficit was noted in all 10 patients with cerebral vasoconstriction. CONCLUSIONS Cerebral vasoconstriction may occur after carotid artery stenting more frequently than expected. It occurs more frequently in patients with near-total occlusion and with isolation of the cerebral circulation. A large-scale study is necessary to assess the clinical implications of cerebral vasoconstriction after carotid artery stenting.
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Affiliation(s)
- C H Kang
- From the Departments of Radiology (C.H.K., J.R., J.A.Y., S.K.B.)
| | - J Roh
- From the Departments of Radiology (C.H.K., J.R., J.A.Y., S.K.B.)
| | - J A Yeom
- From the Departments of Radiology (C.H.K., J.R., J.A.Y., S.K.B.)
| | - S H Ahn
- Neurology (S.H.A., M.G.P., K.P.P.), Pusan National University Yangsan Hospital, Pusan National University School of Medicine, Yangsan, Korea
| | - M G Park
- Neurology (S.H.A., M.G.P., K.P.P.), Pusan National University Yangsan Hospital, Pusan National University School of Medicine, Yangsan, Korea
| | - K P Park
- Neurology (S.H.A., M.G.P., K.P.P.), Pusan National University Yangsan Hospital, Pusan National University School of Medicine, Yangsan, Korea
| | - S K Baik
- From the Departments of Radiology (C.H.K., J.R., J.A.Y., S.K.B.)
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Abstract
PURPOSE OF REVIEW Cerebral autoregulation (CA) is a mechanism that maintains cerebral blood flow constant despite fluctuations in systemic arterial blood pressure. This review will focus on recent studies that measured CA non-invasively in acute cerebrovascular events, a feature unique to the transcranial Doppler ultrasound. We will summarize the rationale for CA assessment in acute cerebrovascular disorders and specifically evaluate the existing data on the value of CA measures in relation to clinical severity, guiding management decisions, and prognostication. RECENT FINDINGS Existing data suggest that CA is generally impaired in various cerebrovascular disorders. In patients with small vessel ischemic stroke, CA has been shown to be impaired in both hemispheres, whereas in large territorial strokes, CA impairment has been limited to the affected hemisphere. In these latter patients, impaired CA is also predictive of secondary complications such as hemorrhagic transformation and cerebral edema, hence worse functional outcome. In patients with carotid stenosis, impaired CA may also be associated with a higher ipsilateral hemispheric stroke risk. CA is also strongly linked to outcome in patients with intracranial hemorrhage. In patients with intraparenchymal hemorrhage, CA impairment correlated with clinical and imaging severity, whereas in those with subarachnoid hemorrhage, CA measures have a predictive value for development of delayed cerebral ischemia and radiographic vasospasm. Assessment of CA is increasingly more accessible in acute cerebrovascular disorders and promises to be a valuable measure in guiding hemodynamic management and predicting secondary complication, thus enhancing the care of these patients in the acute setting.
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Affiliation(s)
- Pedro Castro
- Department of Neurology, São João Hospital Center, Porto, Portugal.,Department of Clinical Neurosciences and Mental Health, Faculty of Medicine of University of Porto, Porto, Portugal
| | - Elsa Azevedo
- Department of Neurology, São João Hospital Center, Porto, Portugal.,Department of Clinical Neurosciences and Mental Health, Faculty of Medicine of University of Porto, Porto, Portugal
| | - Farzaneh Sorond
- Department of Neurology, Division of Stroke and Neurocritical, Northwestern University Feinberg School of Medicine, 303 East Chicago Avenue, Ward 12-140, Chicago, IL, 60611, USA.
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Qureshi AI, Saleem MA, Naseem N, Wallery SS. A New Technique for the Assessment of Cerebral Vasodilatory Capacity as Part of Catheter-Based Cerebral Angiography. J Stroke Cerebrovasc Dis 2018; 27:1822-1827. [PMID: 29571761 DOI: 10.1016/j.jstrokecerebrovasdis.2018.02.027] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Accepted: 02/10/2018] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Previous studies have demonstrated the value of cerebral vasodilatory capacity assessment for risk stratification in patients with extracranial arterial stenosis or occlusion. We describe a new method that assesses cerebral vasodilatory capacity as part of catheter-based cerebral angiography. METHODS We assessed regional cerebral blood volume (rCBV) in the arterial distribution of interest using a controlled contrast injection through a diagnostic catheter placed in the common carotid or the subclavian artery. rCBV maps were created using predefined algorithm based on contrast distribution in the venous phase (voxel size 0.466 mm3) into high, intermediate, low, and no detectable rCBV regions. rCBV maps were acquired again after the administration of intra-arterial nicardipine (1.5-2.5 mg), and percentage increases of the area of various grades of rCBV were calculated. RESULTS Three patients with internal carotid artery stenosis (32% - 64% in severity) and 1 patient with extracranial vertebral artery stenosis (46% in severity) were assessed. There was a variable but consistent increase in the area of high rCBV in the ipsilateral hemisphere in 3 patients with internal carotid artery flow (5.5%-24.5%) and the cerebellum (9.6%) in 1 patient with vertebral artery flow assessments. The increase in high rCBV was most prominent in the patient who received 2.5 mg (24.5%) and least prominent in a patient who received 1.5 mg (5.5%) of intra-arterial nicardipine. There was a concurrent reduction in areas of intermediate and low rCBV (shift) in 3 patients, and there was an increase in all areas of rCBV grades (addition) in 1 patient. CONCLUSIONS Selective assessment of cerebral vasodilatory response in the affected arterial distribution is feasible during catheter-based cerebral angiography.
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Affiliation(s)
- Adnan I Qureshi
- Zeenat Qureshi Stroke Institute, St. Cloud, Minnesota; University of Illinois and Mercyhealth, Rockford, Illinois
| | - Muhammad A Saleem
- Zeenat Qureshi Stroke Institute, St. Cloud, Minnesota; Mercyhealth, Janesville, Wisconsin.
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Semenyutin VB, Asaturyan GA, Nikiforova AA, Aliev VA, Panuntsev GK, Iblyaminov VB, Savello AV, Patzak A. Predictive Value of Dynamic Cerebral Autoregulation Assessment in Surgical Management of Patients with High-Grade Carotid Artery Stenosis. Front Physiol 2017; 8:872. [PMID: 29163214 PMCID: PMC5673646 DOI: 10.3389/fphys.2017.00872] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2017] [Accepted: 10/17/2017] [Indexed: 01/20/2023] Open
Abstract
Dynamic cerebral autoregulation (DCA) capacity along with the degree of internal carotid artery (ICA) stenosis and characteristics of the plaque can also play an important role in selection of appropriate treatment strategy. This study aims to classify the patients with severe ICA stenosis according to preoperative state of DCA and to assess its dynamics after surgery. Thirty-five patients with severe ICA stenosis having different clinical type of disease underwent reconstructive surgery. DCA was assessed with transfer function analysis (TFA) by calculating phase shift (PS) between Mayer waves of blood flow velocity (BFV) and blood pressure (BP) before and after operation. In 18 cases, regardless of clinical type, preoperative PS on ipsilateral side was within the normal range and did not change considerably after surgery. In other 17 cases preoperative PS was reliably lower both in patients with symptomatic and asymptomatic stenosis. Surgical reconstruction led to restoration of impaired DCA evidenced by significant increase of PS in postoperative period. Our data suggest that regardless clinical type of disease various state of DCA may be present in patients with severe ICA stenosis. This finding can contribute to establishing the optimal treatment strategy, and first of all for asymptomatic patients. Patients with compromised DCA should be considered as ones with higher risk of stroke and first candidates for reconstructive surgery.
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Affiliation(s)
- Vladimir B Semenyutin
- Laboratory of Brain Circulation Pathology, Federal Almazov Medical Research Center, Saint-Petersburg, Russia
| | - Gregory A Asaturyan
- Laboratory of Brain Circulation Pathology, Federal Almazov Medical Research Center, Saint-Petersburg, Russia
| | - Anna A Nikiforova
- Laboratory of Brain Circulation Pathology, Federal Almazov Medical Research Center, Saint-Petersburg, Russia
| | - Vugar A Aliev
- Laboratory of Brain Circulation Pathology, Federal Almazov Medical Research Center, Saint-Petersburg, Russia.,Department of Neurosurgery, Municipal Hospital of Saint Martyr Elizabeth, Saint-Petersburg, Russia
| | - Grigory K Panuntsev
- Laboratory of Brain Circulation Pathology, Federal Almazov Medical Research Center, Saint-Petersburg, Russia
| | - Vadim B Iblyaminov
- Laboratory of Brain Circulation Pathology, Federal Almazov Medical Research Center, Saint-Petersburg, Russia
| | - Alexander V Savello
- Laboratory of Brain Circulation Pathology, Federal Almazov Medical Research Center, Saint-Petersburg, Russia
| | - Andreas Patzak
- Johannes-Mueller Institute of Physiology University Hospital Charite, Humboldt University of Berlin, Berlin, Germany
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Ellis MJ, Ryner LN, Sobczyk O, Fierstra J, Mikulis DJ, Fisher JA, Duffin J, Mutch WAC. Neuroimaging Assessment of Cerebrovascular Reactivity in Concussion: Current Concepts, Methodological Considerations, and Review of the Literature. Front Neurol 2016; 7:61. [PMID: 27199885 PMCID: PMC4850165 DOI: 10.3389/fneur.2016.00061] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Accepted: 04/11/2016] [Indexed: 01/07/2023] Open
Abstract
Concussion is a form of traumatic brain injury (TBI) that presents with a wide spectrum of subjective symptoms and few objective clinical findings. Emerging research suggests that one of the processes that may contribute to concussion pathophysiology is dysregulation of cerebral blood flow (CBF) leading to a mismatch between CBF delivery and the metabolic needs of the injured brain. Cerebrovascular reactivity (CVR) is defined as the change in CBF in response to a measured vasoactive stimulus. Several magnetic resonance imaging (MRI) techniques can be used as a surrogate measure of CBF in clinical and laboratory studies. In order to provide an accurate assessment of CVR, these sequences must be combined with a reliable, reproducible vasoactive stimulus that can manipulate CBF. Although CVR imaging currently plays a crucial role in the diagnosis and management of many cerebrovascular diseases, only recently have studies begun to apply this assessment tool in patients with concussion. In order to evaluate the quality, reliability, and relevance of CVR studies in concussion, it is important that clinicians and researchers have a strong foundational understanding of the role of CBF regulation in health, concussion, and more severe forms of TBI, and an awareness of the advantages and limitations of currently available CVR measurement techniques. Accordingly, in this review, we (1) discuss the role of CVR in TBI and concussion, (2) examine methodological considerations for MRI-based measurement of CVR, and (3) provide an overview of published CVR studies in concussion patients.
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Affiliation(s)
- Michael J Ellis
- Department of Surgery, University of Manitoba, Winnipeg, MB, Canada; Department of Pediatrics and Child Health, University of Manitoba, Winnipeg, MB, Canada; Section of Neurosurgery, University of Manitoba, Winnipeg, MB, Canada; Pan Am Concussion Program, University of Manitoba, Winnipeg, MB, Canada; Childrens Hospital Research Institute of Manitoba, University of Manitoba, Winnipeg, MB, Canada; Canada North Concussion Network, University of Manitoba, Winnipeg, MB, Canada; University of Manitoba, Winnipeg, MB, Canada
| | - Lawrence N Ryner
- Canada North Concussion Network, University of Manitoba, Winnipeg, MB, Canada; Department of Radiology, University of Manitoba, Winnipeg, MB, Canada; Health Sciences Centre, University of Manitoba, Winnipeg, MB, Canada
| | - Olivia Sobczyk
- Institute of Medical Sciences, University of Toronto , Toronto, ON , Canada
| | - Jorn Fierstra
- Department of Neurosurgery, University Hospital Zurich , Zurich , Switzerland
| | - David J Mikulis
- Department of Medical Imaging, University of Toronto, Toronto, ON, Canada; University of Toronto, Toronto, ON, Canada; University Health Network Cerebrovascular Reactivity Research Group, Toronto, ON, Canada
| | - Joseph A Fisher
- University of Toronto, Toronto, ON, Canada; University Health Network Cerebrovascular Reactivity Research Group, Toronto, ON, Canada; Department of Anesthesia, University of Toronto, Toronto, ON, Canada
| | - James Duffin
- University of Toronto, Toronto, ON, Canada; University Health Network Cerebrovascular Reactivity Research Group, Toronto, ON, Canada; Department of Physiology, University of Toronto, Toronto, ON, Canada
| | - W Alan C Mutch
- Canada North Concussion Network, University of Manitoba, Winnipeg, MB, Canada; University of Manitoba, Winnipeg, MB, Canada; Health Sciences Centre, University of Manitoba, Winnipeg, MB, Canada; Department of Anesthesia and Perioperative Medicine, University of Manitoba, Winnipeg, MB, Canada
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Zhang Y, Liu X, Steiner L, Smielewski P, Feen E, Pickard JD, Czosnyka M. Correlation Between Cerebral Autoregulation and Carbon Dioxide Reactivity in Patients with Traumatic Brain Injury. ACTA NEUROCHIRURGICA. SUPPLEMENT 2016; 122:205-9. [PMID: 27165907 DOI: 10.1007/978-3-319-22533-3_41] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
OBJECTIVE Cerebral blood flow autoregulation is commonly impaired in patients with traumatic brain injury (TBI). This study was to investigate correlations between cerebral autoregulation and CO2 reactivity in patients with TBI during transient mild hypocapnia. METHODS Patients with TBI who were on mechanical ventilation were hyperventilated for approximately 60 min. Indices of autoregulation, based on a model of the relationship between arterial blood pressure and blood flow velocity (FV) (ARIabp) and, separately, between cerebral perfusion pressure and FV (ARIcpp), were calculated. Mean flow index (Mx) was also calculated. RESULTS We investigated 31 consecutive patients. At baseline, median PaCO2 was 5.09 kPa (range 4.30-5.67 kPa); during hyperventilation, median PaCO2 was 4.38 kPa (range 3.72-4.96 kPa). ARI was associated with Mx (ARIabp vs. Mx: r = -0.39, p = 0.04; ARIcpp vs Mx: r = -0.67, p < 0.001). CO2 reactivity showed significant correlation with ARIcpp (r = 0.41, p = 0.04) and Mx (r = -0.37, p = 0.04). ARI after hyperventilation was significantly higher than ARI at baseline (ARIcpp: p = 0.02; ARIabp: p < 0.001). CONCLUSIONS Cerebral autoregulation seemed to be well linked to CO2 reactivity during transient hyperventilation. ARIcpp had a stronger correlation with CO2 reactivity than ARIabp. ARI indicated improvement of autoregulation during hyperventilation. Cerebral autoregulation indices (ARI, Mx) were associated with each other.
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Affiliation(s)
- Yi Zhang
- Department of Neurosurgery, University of Cambridge, Cambridge, UK.
- Department of Neurology, University of Rochester Medical Center, 601 Elmwood Avenue, 673, Rochester, NY, 14642, USA.
- Department of Neurology, Saint Louis University, Saint Louis, MO, USA.
| | - Xiuyun Liu
- Department of Neurosurgery, University of Cambridge, Cambridge, UK
| | - Luzius Steiner
- Department of Neurosurgery, University of Cambridge, Cambridge, UK
- Department of Anesthesiology, University Hospital in Basel, Basel, Switzerland
| | - Peter Smielewski
- Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
| | - Eli Feen
- Department of Neurology, Saint Louis University, Saint Louis, MO, USA
| | - John D Pickard
- Department of Neurosurgery, University of Cambridge, Cambridge, UK
| | - Marek Czosnyka
- Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
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Bilateral Failure of Cerebral Autoregulation is Related to Unfavorable Outcome After Subarachnoid Hemorrhage. Neurocrit Care 2014; 22:65-73. [DOI: 10.1007/s12028-014-0032-6] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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10
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Donahue MJ, Faraco CC, Strother MK, Chappell MA, Rane S, Dethrage LM, Hendrikse J, Siero JCW. Bolus arrival time and cerebral blood flow responses to hypercarbia. J Cereb Blood Flow Metab 2014; 34:1243-52. [PMID: 24780904 PMCID: PMC4083394 DOI: 10.1038/jcbfm.2014.81] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/17/2013] [Revised: 04/07/2014] [Accepted: 04/09/2014] [Indexed: 11/09/2022]
Abstract
The purpose of this study was to evaluate how cerebral blood flow and bolus arrival time (BAT) measures derived from arterial spin labeling (ASL) MRI data change for different hypercarbic gas stimuli. Pseudocontinuous ASL (pCASL) was applied (3.0T; spatial resolution=4 × 4 × 7 mm(3); repetition time/echo time (TR/TE)=3,600/11 ms) sequentially in healthy volunteers (n=12; age=30±4 years) for separate experiments in which (i) normocarbic normoxia (i.e., room air), hypercarbic normoxia (i.e., 5% CO₂/21% O₂/74% N2), and hypercarbic hyperoxia (i.e., carbogen: 5% CO₂/95% O₂) gas was administered (12 L/minute). Cerebral blood flow and BAT changes were quantified using models that account for macrovascular signal and partial volume effects in all gray matter and regionally in cerebellar, temporal, occipital, frontal, and parietal lobes. Regional reductions in BAT of 4.6% to 7.7% and 3.3% to 6.6% were found in response to hypercarbic normoxia and hypercarbic hyperoxia, respectively. Cerebral blood flow increased by 8.2% to 27.8% and 3.5% to 19.8% for hypercarbic normoxia and hypercarbic hyperoxia, respectively. These findings indicate that changes in BAT values may bias functional ASL data and thus should be considered when choosing appropriate experimental parameters in calibrated functional magnetic resonance imaging or ASL cerebrovascular reactivity experiments that use hypercarbic gas stimuli.
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Affiliation(s)
- Manus J Donahue
- 1] Radiology and Radiological Sciences, Vanderbilt University School of Medicine, Nashville, Tennessee, USA [2] Psychiatry, Vanderbilt University School of Medicine, Nashville, Tennessee, USA [3] Neurology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA [4] Physics and Astronomy, Vanderbilt University, Nashville, Tennessee, USA
| | - Carlos C Faraco
- Radiology and Radiological Sciences, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - Megan K Strother
- Radiology and Radiological Sciences, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | | | - Swati Rane
- Radiology and Radiological Sciences, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - Lindsey M Dethrage
- Radiology and Radiological Sciences, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - Jeroen Hendrikse
- Radiology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Jeroen C W Siero
- Radiology, University Medical Center Utrecht, Utrecht, The Netherlands
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Fierstra J, Sobczyk O, Battisti-Charbonney A, Mandell DM, Poublanc J, Crawley AP, Mikulis DJ, Duffin J, Fisher JA. Measuring cerebrovascular reactivity: what stimulus to use? J Physiol 2013; 591:5809-21. [PMID: 24081155 DOI: 10.1113/jphysiol.2013.259150] [Citation(s) in RCA: 214] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Cerebrovascular reactivity is the change in cerebral blood flow in response to a vasodilatory or vasoconstrictive stimulus. Measuring variations of cerebrovascular reactivity between different regions of the brain has the potential to not only advance understanding of how the cerebral vasculature controls the distribution of blood flow but also to detect cerebrovascular pathophysiology. While there are standardized and repeatable methods for estimating the changes in cerebral blood flow in response to a vasoactive stimulus, the same cannot be said for the stimulus itself. Indeed, the wide variety of vasoactive challenges currently employed in these studies impedes comparisons between them. This review therefore critically examines the vasoactive stimuli in current use for their ability to provide a standard repeatable challenge and for the practicality of their implementation. Such challenges include induced reductions in systemic blood pressure, and the administration of vasoactive substances such as acetazolamide and carbon dioxide. We conclude that many of the stimuli in current use do not provide a standard stimulus comparable between individuals and in the same individual over time. We suggest that carbon dioxide is the most suitable vasoactive stimulus. We describe recently developed computer-controlled MRI compatible gas delivery systems which are capable of administering reliable and repeatable vasoactive CO2 stimuli.
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Affiliation(s)
- J Fierstra
- J. Duffin: Department of Physiology, Medical Sciences Building, 1 King's College Circle, University of Toronto, Toronto, Ontario, Canada, M5S 1A8.
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12
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Czosnyka M, Smielewski P, Lavinio A, Czosnyka Z, Pickard JD. A synopsis of brain pressures: which? when? are they all useful? Neurol Res 2013; 29:672-9. [DOI: 10.1179/016164107x240053] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
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Liu YJ, Huang TY, Lee YH, Juan CJ. The cerebral vasomotor response in varying CO(2) concentrations, as evaluated using cine phase contrast MRI: Flow, volume, and cerebrovascular resistance indices. Med Phys 2013; 39:6534-41. [PMID: 23127048 DOI: 10.1118/1.4754806] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
PURPOSE Previous studies have identified that impaired cerebral vasomotor reactivity (VMR) is associated with a higher risk of stroke and transient ischemic attack. This study aims to evaluate VMR by measuring the blood flow waveforms of the supplying arteries and dural sinuses using cine phase contrast MRI (PC MRI) and hypercapnic challenge. METHODS PC MRI flow quantification was performed on an oblique slice approximately perpendicular to the target vessels to include the left (LICA) and right internal carotid artery (RICA), basilar artery (BA), sinus rectus (SR), and superior sagittal sinus (SSS). A total of four PC MRI scans were performed at different CO(2) concentrations (room air and 3%, 5%, and 7% CO(2)). RESULTS The analyses obtained the flow parameters and cerebrovascular resistance parameters for all five vessels. Results indicated that the vascular resistance indices decreased with increasing CO(2) concentration in four vessels (LICA, RICA, BA, and SR). The obtained VMR parameters demonstrated exponential increases with increasing CO(2) concentration. CONCLUSIONS Using entire blood flow waveforms, this study applied separate flow dynamics during systolic and diastolic periods to obtain cerebrovascular resistance parameters and extensive flow-related information. It is the first to investigate the cerebrovascular resistance parameters under hypercapnic challenge using cine MRI. This technique could provide a useful tool for clinical application in cerebrovascular disease.
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Affiliation(s)
- Yi-Jui Liu
- Department of Automatic Control Engineering, Feng Chia University, Taichung, Taiwan, Republic of China
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14
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Wong GKC, Poon WS. Letter by Wong and Poon Regarding Article, “Does Impaired Cerebrovascular Reactivity Predict Stroke Risk in Asymptomatic Carotid Stenosis? A Prospective Substudy of the Asymptomatic Carotid Emboli Study (ACES)”. Stroke 2011; 42:e565. [DOI: 10.1161/strokeaha.111.630889] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- George Kwok-Chu Wong
- Division of Neurosurgery Prince of Wales Hospital Chinese University of Hong Kong Hong Kong (Wong, Poon)
| | - Wai Sang Poon
- Division of Neurosurgery Prince of Wales Hospital Chinese University of Hong Kong Hong Kong (Wong, Poon)
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15
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Schytz HW, Hansson A, Phillip D, Selb J, Boas DA, Iversen HK, Ashina M. Spontaneous low-frequency oscillations in cerebral vessels: applications in carotid artery disease and ischemic stroke. J Stroke Cerebrovasc Dis 2011; 19:465-74. [PMID: 20864356 DOI: 10.1016/j.jstrokecerebrovasdis.2010.06.001] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2009] [Accepted: 12/02/2009] [Indexed: 11/30/2022] Open
Abstract
The etiology behind and physiological significance of spontaneous oscillations in the low-frequency spectrum in both systemic and cerebral vessels remain unknown. Experimental studies have proposed that spontaneous oscillations in cerebral blood flow reflect impaired cerebral autoregulation (CA). Analysis of CA by measurement of spontaneous oscillations in the low-frequency spectrum in cerebral vessels might be a useful tool for assessing risk and investigating different treatment strategies in carotid artery disease (CAD) and stroke. We reviewed studies exploring spontaneous oscillations in the low-frequency spectrum in patients with CAD and ischemic stroke, conditions known to involve impaired CA. Several studies have reported changes in oscillations after CAD and stroke after surgery and over time compared with healthy controls. Phase shift in the frequency domain and correlation coefficients in the time domain are the most frequently used parameters for analyzing spontaneous oscillations in systemic and cerebral vessels. At present, there is no gold standard for analyzing spontaneous oscillations in the low-frequency spectrum, and simplistic models of CA have failed to predict or explain the spontaneous oscillation changes found in CAD and stroke studies. Near-infrared spectroscopy is suggested as a future complementary tool for assessing changes affecting the cortical arterial system.
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Affiliation(s)
- Henrik W Schytz
- Danish Headache Center, Department of Neurology, Glostrup Hospital, Faculty of Health Sciences, University of Copenhagen, Glostrup, Denmark.
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16
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Nasr N, Czosnyka M, Arevalo F, Hanaire H, Guidolin B, Larrue V. Autonomic neuropathy is associated with impairment of dynamic cerebral autoregulation in type 1 diabetes. Auton Neurosci 2010; 160:59-63. [PMID: 21036672 DOI: 10.1016/j.autneu.2010.10.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2010] [Revised: 09/07/2010] [Accepted: 10/04/2010] [Indexed: 11/30/2022]
Abstract
HYPOTHESIS The mechanisms underlying impairment of dynamic cerebral autoregulation in diabetes are not well known. Cardiovascular autonomic neuropathy (CAN) could contribute to dynamic cerebral autoregulation impairment. In this study, we assessed the association between CAN and impairment of dynamic cerebral autoregulation in patients with type 1 diabetes. METHODS We evaluated dynamic cerebral autoregulation (DCA) in patients with type 1 diabetes and no history of cerebrovascular disease. DCA was assessed with transcranial Doppler using the correlation coefficient index Mx method. Mx was calculated from slow changes in mean cerebral blood flow velocity and mean arterial blood pressure. Increase in Mx indicates weaker DCA, with a threshold for impaired DCA above 0.3. Moderate CAN was defined as reduced heart rate variability (HRV) on the following tests: deep controlled breathing, Valsalva maneuver or initiation of active standing. Severe CAN was defined as reduced HRV associated with orthostatic hypotension. RESULTS 60 patients were included (M/F: 33/27; mean age ± SD: 46 years ± 11.5). 23 patients had moderate CAN and 15 patients severe CAN. DCA was impaired in 37 patients. CAN was associated with impaired DCA (p = 0.005). Impairment of DCA was more pronounced in patients with severe CAN (p = 0.019). Glycosylated haemoglobin (HbA1c) was associated with impaired DCA in univariate analysis (p = 0.05). In multivariate analysis, only CAN was associated with impaired DCA (p = 0.007) whereas HbA1c was not (p = 0.161). CONCLUSIONS CAN was associated with impaired DCA in type 1 diabetes. The magnitude of DCA impairment increased with the severity of CAN.
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Affiliation(s)
- N Nasr
- Service de Neurologie Vasculaire, Hôpital Rangueil, Toulouse, INSERM U, France.
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17
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Ursino M, Giannessi M. A Model of Cerebrovascular Reactivity Including the Circle of Willis and Cortical Anastomoses. Ann Biomed Eng 2010; 38:955-74. [DOI: 10.1007/s10439-010-9923-7] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2008] [Accepted: 01/07/2010] [Indexed: 01/26/2023]
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18
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Nasr N, Traon APL, Czosnyka M, Tiberge M, Schmidt E, Larrue V. Cerebral autoregulation in patients with obstructive sleep apnea syndrome during wakefulness. Eur J Neurol 2009; 16:386-91. [DOI: 10.1111/j.1468-1331.2008.02505.x] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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19
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Monitoring of cerebrovascular autoregulation: facts, myths, and missing links. Neurocrit Care 2009; 10:373-86. [PMID: 19127448 DOI: 10.1007/s12028-008-9175-7] [Citation(s) in RCA: 240] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2008] [Accepted: 12/02/2008] [Indexed: 12/16/2022]
Abstract
UNLABELLED The methods for continuous assessment of cerebral autoregulation using correlation, phase shift, or transmission (either in time- or frequency-domain) were introduced a decade ago. They express dynamic relationships between slow waves of transcranial Doppler (TCD), blood flow velocity (FV) and cerebral perfusion pressure (CPP), or arterial pressure (ABP). We review a methodology and clinical application of indices useful for monitoring cerebral autoregulation and pressure-reactivity in various scenarios of neuro-critical care. FACTS Poor autoregulation and loss of pressure-reactivity are independent predictors of fatal outcome following head injury. Autoregulation is impaired by too low or too high CPP when compared to autoregulation with normal CPP (usually between 60 and 85 mmHg; and these limits are highly individual). Hemispheric asymmetry of the bi-laterally assessed autoregulation has been associated with asymmetry of CT scan findings: autoregulation was found to be worse ipsilateral to contusion or lateralized edema causing midline shift. The pressure-reactivity (PRx index) correlated with a state of low CBF and CMRO2 revealed using PET studies. The PRx is easier to monitor over prolonged periods of time than the TCD-based indices as it does not require fixation of external probes. Continuous monitoring with the PRx can be used to direct CPP-oriented therapy by determining the optimal CPP for pressure-reactivity. Autoregulation indices are able to reflect transient changes of autoregulation, as seen during plateau waves of ICP. However, minute-to-minute assessment of autoregulation has a poor signal-to-noise ratio. Averaging across time (30 min) or by combining with other relevant parameters improves the accuracy. MYTHS: It is debatable whether the TCD-based indices in head injured patients can be calculated using ABP instead of CPP. Thresholds for functional and disturbed autoregulation dramatically depends on arterial tension of CO2--therefore, comparison between patients cannot be performed without comparing their PaCO2. The TCD pulsatility index cannot accurately detect the lower limit of autoregulation. MISSING LINKS: We still do not know whether autoregulation-oriented therapy can be understood as a consensus between CPP-directed protocols and the Lund-concept. What are the links between endothelial function and autoregulation indices? Can autoregulation after head injury be improved with statins or EPO, as in subarachnoid hemorrhage? In conclusion, monitoring cerebral autoregulation can be used in a variety of clinical scenarios and may be helpful in delineating optimal therapeutic strategies.
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20
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KUNZ ALEXANDER, IADECOLA COSTANTINO. Cerebral vascular dysregulation in the ischemic brain. HANDBOOK OF CLINICAL NEUROLOGY 2009; 92:283-305. [PMID: 18790280 PMCID: PMC3982865 DOI: 10.1016/s0072-9752(08)01914-3] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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21
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Near-infrared spectroscopy can monitor dynamic cerebral autoregulation in adults. Neurocrit Care 2008; 10:122-8. [PMID: 18807218 DOI: 10.1007/s12028-008-9140-5] [Citation(s) in RCA: 116] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2008] [Accepted: 08/15/2008] [Indexed: 10/21/2022]
Abstract
OBJECTIVE To study the correlation between a dynamic index of cerebral autoregulation assessed with blood flow velocity (FV) using transcranial Doppler, and a tissue oxygenation index (TOI) recorded with near-infrared spectroscopy (NIRS). METHODS Twenty-three patients with sepsis, severe sepsis, or septic shock were monitored daily on up to four consecutive days. FV, TOI, and mean arterial blood pressure (ABP) were recorded for 60 min every day. An index of autoregulation (Mx) was calculated as the moving correlation coefficient between 10-s averaged values of FV and ABP over moving 5 min time-windows. The index Tox was evaluated as the correlation coefficient between TOI and ABP in the same way. The indices Mx and Tox, ABP and arterial partial pressure of CO(2) were averaged for each patient. RESULTS Synchronized slow waves, presenting with periods from 20 s to 2 min, were seen in the TOI and FV of most patients, with a reasonable coherence between the signals in this bandwidth (coherence >0.5). The indices, Mx and Tox, demonstrated good correlation with each other (R = 0.81; P < 0.0001) in the whole group of patients. Both indices showed a significant (P < 0.05) tendency to indicate weaker autoregulation in the state of vasodilatation associated with greater values of arterial partial pressure of CO(2) or lower values of ABP. CONCLUSION NIRS shows promise for the continuous assessment of cerebral autoregulation in adults.
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22
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Cerebral dysautoregulation and the risk of ischemic events in occlusive carotid artery disease. J Neurol 2008; 255:1182-9. [DOI: 10.1007/s00415-008-0865-z] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2007] [Revised: 12/03/2007] [Accepted: 01/08/2008] [Indexed: 11/27/2022]
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23
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Czosnyka M, Smielewski P, Lavinio A, Pickard JD, Panerai R. An Assessment of Dynamic Autoregulation from Spontaneous Fluctuations of Cerebral Blood Flow Velocity: A Comparison of Two Models, Index of Autoregulation and Mean Flow Index. Anesth Analg 2008; 106:234-9, table of contents. [DOI: 10.1213/01.ane.0000295802.89962.13] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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24
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Piechnik SK, Chiarelli PA, Jezzard P. Modelling vascular reactivity to investigate the basis of the relationship between cerebral blood volume and flow under CO2 manipulation. Neuroimage 2007; 39:107-18. [PMID: 17920935 DOI: 10.1016/j.neuroimage.2007.08.022] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2007] [Revised: 08/08/2007] [Accepted: 08/21/2007] [Indexed: 10/22/2022] Open
Abstract
Changes in cerebral blood flow (f) and vascular volume (v) are of major interest in mapping cerebral activity and metabolism, but the relation between them currently lacks a sufficient theoretical basis. To address this we considered three models: a uniform reactive tube model (M1); an extension of M1 that includes passive arterial inflow and venous volume (M2); and a more anatomically plausible model (M3) consisting of 19 compartments representing the whole range of vascular sizes and respective CO2 reactivities, derived from literature data. We find that M2 cannot be described as the simple scaling of a tube law, but any divergence from a linear approximation is negligible within the narrow physiological range encountered experimentally. In order to represent correctly the empirically observed slope of the overall v-f relationship, the reactive bed should constitute about half of the total vascular volume, thus including a significant fraction of capillaries and/or veins. Model M3 demonstrates systematic variation of the slope of the v-f relationship between 0.16 and 1.0, depending on the vascular compartment under consideration. This is further complicated when other experimental approaches such as flow velocity are used as substitute measurements. The effect is particularly large in microvascular compartments, but when averaged with larger vessels the variations in slope are contained within 0.25 to 0.55 under conditions typical for imaging methods. We conclude that the v-f relationship is not a fixed function but that both the shape and slope depend on the composition of the reactive volume and the experimental methods used.
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Affiliation(s)
- Stefan K Piechnik
- Oxford Centre for Functional Magnetic Resonance Imaging of the Brain, University of Oxford, John Radcliffe Hospital, Oxford, OX3 9DU, UK.
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25
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Smielewski P, Czosnyka M, Steiner L, Belestri M, Piechnik S, Pickard JD. ICM+: software for on-line analysis of bedside monitoring data after severe head trauma. ACTA NEUROCHIRURGICA. SUPPLEMENT 2006; 95:43-9. [PMID: 16463818 DOI: 10.1007/3-211-32318-x_10] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
ICM software was developed in 1986 in Warsaw, Poland and has been in use at the University of Cambridge Neurocritical Care Unit for 10 years collecting data from bed-side monitors in nearly 600 severely head injured patients and calculating secondary indices describing cerebral autoregulation and pressure-volume compensation. The new software ICM+ includes a much extended calculation engine that allows easy configuration and on-line trending of complex parameters. The program records raw signals, and calculates time trends of summary parameters. Configuration and analysis utilises arithmetic expressions of signal processing functions to calculate various statistical properties for each signal, frequency spectrums and derivatives, as well as correlations/cross-correlations between signals. The software allows configuration of several levels of analysis before calculating the final time trends. The final data are displayed in a variety of ways including simple time trends, as well as time window based histograms, cross histograms, correlations etc. All this allows complex information coming off the bed-side monitors to be summarized in a concise fashion and presented to medical and nursing staff in a simple way that alerts them to the development of various pathological processes. The system provides a universal tool for clinical and academic purposes. Its flexibility and advanced signal processing is specialized for the needs of multidisciplinary brain monitoring.
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Affiliation(s)
- P Smielewski
- Academic Department of Neurosurgery, Addenbrooke's Hospital, Cambridge, UK.
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26
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Kumar A, Schmidt EA, Hiler M, Smielewski P, Pickard JD, Czosnyka M. Asymmetry of critical closing pressure following head injury. J Neurol Neurosurg Psychiatry 2005; 76:1570-3. [PMID: 16227554 PMCID: PMC1739415 DOI: 10.1136/jnnp.2004.059493] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
OBJECTIVE Critical closing pressure (CCP) is the arterial pressure below which the vessels collapse. Hypothetically it is the sum of intracranial pressure (ICP) and vessel wall tension in the cerebral circulation. This study investigated transhemispherical asymmetry of CCP by studying its correlation with radiological findings on computed tomography (CT) scans in head injury patients. METHOD ICP, arterial blood pressure, and middle cerebral artery blood flow velocity were recorded daily in 119 ventilated patients. Waveforms were processed to calculate CCP. CT scans were analysed according to a system based on the Marshall classification. RESULTS Left-right differences in CCP correlated with midline shift on the CT scan (r = 0.48; p<0.02). Asymmetry of CCP also corresponded with the side of the head lesion (p<0.007) and the side of the craniotomy where it was performed (p<0.006). Absolute CCP weakly correlated with brain swelling (r = -0.23; p<0.03) and arterial pressure (r = 0.21; p<0.02) but did not correlate with ICP. Cerebral perfusion pressure calculated as the difference between mean arterial pressure and CCP did not correlate with outcome, but "traditional" cerebral perfusion pressure (mean arterial pressure minus intracranial pressure) did. CONCLUSIONS Critical closing pressure is disturbed by localised brain lesions. Its asymmetry corresponds to asymmetrical findings on CT scans. CCP seems to describe vascular resistance better than ICP.
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Affiliation(s)
- A Kumar
- University of Cambridge Clinical School, Addenbrooke's Hospital, UK
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27
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Reinhard M, Roth M, Guschlbauer B, Harloff A, Timmer J, Czosnyka M, Hetzel A. Dynamic Cerebral Autoregulation in Acute Ischemic Stroke Assessed From Spontaneous Blood Pressure Fluctuations. Stroke 2005; 36:1684-9. [PMID: 16020768 DOI: 10.1161/01.str.0000173183.36331.ee] [Citation(s) in RCA: 115] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Background and Purpose—
This study investigates dynamic cerebral autoregulation assessed from spontaneous blood pressure (ABP) and cerebral blood flow velocity (CBFV) fluctuations and its time course in acute ischemic stroke.
Methods—
Forty patients admitted with acute ischemic stroke in the territory of the middle cerebral artery (MCA) were enrolled. Admission National Institutes of Health Stroke score was 6±4. Study 1 was performed within 22 (±11) hours and study 2 was performed within 134 (±25) hours of ictus. The final analysis comprised 33 and 29 patients for study 1 and study 2, respectively. Twenty-five age- and sex-matched controls were studied. ABP (Finapres method) and CBFV in both MCAs (transcranial Doppler) were recorded over 10 minutes. Correlations between diastolic and mean ABP and CBFV fluctuations were averaged, yielding the correlation coefficient indices (Dx, Mx). Transfer function analysis was applied to obtain phase shift and gain between ABP and CBFV oscillations.
Results—
No disturbance of autoregulation was indicated by all parameters at study 1. Separate analyses for clinical severity, stroke side, and size did not reveal significant differences for the various autoregulatory indices at study 1 and 2. At study 2, MCA flow velocity was significantly increased on both sides, the autoregulation index Mx was slightly but significantly (
P
<0.05) worse on both sides in comparison to study 1, and phase showed a trend toward poorer values on affected sides. No significant differences to controls occurred. Clinical outcome in patients completing both studies was good in all but one patient.
Conclusions—
Dynamic cerebral autoregulation assessed from spontaneous blood pressure fluctuations does not seem to be relevantly disturbed in early minor MCA stroke. At the subacute stage, slight autoregulatory disturbance may be present.
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Affiliation(s)
- M Reinhard
- Department of Neurology and Clinical Neurophysiology, University of Freiburg, Germany.
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Reinhard M, Roth M, Müller T, Guschlbauer B, Timmer J, Czosnyka M, Hetzel A. Effect of Carotid Endarterectomy or Stenting on Impairment of Dynamic Cerebral Autoregulation. Stroke 2004; 35:1381-7. [PMID: 15087557 DOI: 10.1161/01.str.0000127533.46914.31] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Background and Purpose—
Analysis of dynamic cerebral autoregulation (DCA) from spontaneous blood pressure fluctuations might contribute to prognosis of severe internal carotid artery stenosis, but its response to carotid recanalization has not been investigated so far. This study investigates the effect of carotid endarterectomy or stenting on various DCA parameters.
Methods—
In 58 patients with severe unilateral stenosis undergoing carotid endarterectomy (n=41) or stenting (n=17), cerebral blood flow velocity (CBFV, transcranial Doppler) and arterial blood pressure (ABP, Finapres method) were recorded over 10 minutes before and on average 3 days after carotid recanalization. Nineteen patients were additionally examined after 7 months. Correlations between diastolic and mean ABP and CBFV fluctuations were averaged to form the correlation coefficient indices (diastolic [Dx] and mean values [Mx]). Transfer function parameters (low-frequency phase and high-frequency gain between ABP and CBFV oscillations) were calculated over the same 10 minutes. CO
2
reactivity was assessed via inhalation of 7% CO
2
.
Results—
Before recanalization, all DCA parameters were clearly impaired ipsilaterally compared with contralateral sides. Phase, Dx, and Mx indicated early normalization of DCA after both endarterectomy and stenting. By multiple regression, the degree of DCA improvement was highly significantly related to the extent of impairment before recanalization. No significant change in DCA was found at follow-up. Ipsilateral gain and CO
2
reactivity increased significantly less after endarterectomy than after stenting (
P
<0.05).
Conclusions—
Dynamic cerebral dysautoregulation in patients with severe carotid obstruction is readily and completely remedied by carotid recanalization.
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Affiliation(s)
- M Reinhard
- Department of Neurology and Clinical Neurophysiology, University of Freiburg, Germany
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Schmidt EA, Czosnyka M, Steiner LA, Balestreri M, Smielewski P, Piechnik SK, Matta BF, Pickard JD. Asymmetry of pressure autoregulation after traumatic brain injury. J Neurosurg 2004; 99:991-8. [PMID: 14705726 DOI: 10.3171/jns.2003.99.6.0991] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
OBJECT The aim of this study was to assess the asymmetry of autoregulation between the left and right sides of the brain by using bilateral transcranial Doppler ultrasonography in a cohort of patients with head injuries. METHODS Ninety-six patients with head injuries comprised the study population. All significant intracranial mass lesions were promptly removed. The patients were given medications to induce sedation and paralysis, and artificial ventilation. Arterial blood pressure (ABP) and intracranial pressure (ICP) were monitored in an invasive manner. A strategy based on the patient's cerebral perfusion pressure (CPP = ABP - ICP) was applied: CPP was maintained at a level higher than 70 mm Hg and ICP at a level lower than 25 mm Hg. The left and right middle cerebral arteries were insonated daily, and bilateral flow velocities (FVs) were recorded. The correlation coefficient between the CPP and FV, termed Mx, was calculated and time-averaged over each recording period on both sides. An Mx close to 1 signified that slow fluctuations in CPP produced synchronized slow changes in FV, indicating a defective autoregulation. An Mx close to 0 indicated preserved autoregulation. Computerized tomography scans in all patients were reviewed; the side on which the major brain lesion was located was noted and the extent of the midline shift was determined. Outcome was measured 6 months after discharge. The left-right difference in the Mx between the hemispheres was significantly higher in patients who died than in those who survived (0.16 +/- 0.04 compared with 0.08 +/- 0.01; p = 0.04). The left-right difference in the Mx was correlated with a midline shift (r = -0.42; p = 0.03). Autoregulation was worse on the side of the brain where the lesion was located (p < 0.035). CONCLUSIONS The left-right difference in autoregulation is significantly associated with a fatal outcome. Autoregulation in the brain is worse on the side ipsilateral to the lesion and on the side of expansion in cases in which there is a midline shift.
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Affiliation(s)
- Eric A Schmidt
- Academic Neurosurgery Unit, Department of Anaesthesiology, Addenbrooke's Hospital, Cambridge, United Kingdom
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