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Alkhachroum A, Kromm J, De Georgia MA. Big data and predictive analytics in neurocritical care. Curr Neurol Neurosci Rep 2022; 22:19-32. [PMID: 35080751 DOI: 10.1007/s11910-022-01167-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/15/2021] [Indexed: 11/26/2022]
Abstract
PURPOSE OF REVIEW To describe predictive data and workflow in the intensive care unit when managing neurologically ill patients. RECENT FINDINGS In the era of Big Data in medicine, intensive critical care units are data-rich environments. Neurocritical care adds another layer of data with advanced multimodal monitoring to prevent secondary brain injury from ischemia, tissue hypoxia, and a cascade of ongoing metabolic events. A step closer toward personalized medicine is the application of multimodal monitoring of cerebral hemodynamics, bran oxygenation, brain metabolism, and electrophysiologic indices, all of which have complex and dynamic interactions. These data are acquired and visualized using different tools and monitors facing multiple challenges toward the goal of the optimal decision support system. In this review, we highlight some of the predictive data used to diagnose, treat, and prognosticate the neurologically ill patients. We describe information management in neurocritical care units including data acquisition, wrangling, analysis, and visualization.
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Affiliation(s)
- Ayham Alkhachroum
- Miller School of Medicine, Neurocritical Care Division, Department of Neurology, University of Miami, Miami, FL, 33146, USA
| | - Julie Kromm
- Cumming School of Medicine, Department of Critical Care Medicine, University of Calgary, Calgary, AB, Canada
- Cumming School of Medicine, Department of Clinical Neurosciences, University of Calgary, Calgary, AB, Canada
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada
| | - Michael A De Georgia
- Center for Neurocritical Care, Neurological Institute, University Hospital Cleveland Medical Center, 11100 Euclid Avenue, Cleveland, OH, 44106-5040, USA.
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Ipertensione intracranica. Neurologia 2021. [DOI: 10.1016/s1634-7072(21)44503-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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Stocker RA. Intensive Care in Traumatic Brain Injury Including Multi-Modal Monitoring and Neuroprotection. Med Sci (Basel) 2019; 7:medsci7030037. [PMID: 30813644 PMCID: PMC6473302 DOI: 10.3390/medsci7030037] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Revised: 02/01/2019] [Accepted: 02/14/2019] [Indexed: 12/20/2022] Open
Abstract
Moderate to severe traumatic brain injuries (TBI) require treatment in an intensive care unit (ICU) in close collaboration of a multidisciplinary team consisting of different medical specialists such as intensivists, neurosurgeons, neurologists, as well as ICU nurses, physiotherapists, and ergo-/logotherapists. Major goals include all measurements to prevent secondary brain injury due to secondary brain insults and to optimize frame conditions for recovery and early rehabilitation. The distinction between moderate and severe is frequently done based on the Glascow Coma Scale and therefore often is just a snapshot at the early time of assessment. Due to its pathophysiological pathways, an initially as moderate classified TBI may need the same sophisticated surveillance, monitoring, and treatment as a severe form or might even progress to a severe and difficult to treat affection. As traumatic brain injury is rather a syndrome comprising a range of different affections to the brain and as, e.g., age-related comorbidities and treatments additionally may have a great impact, individual and tailored treatment approaches based on monitoring and findings in imaging and respecting pre-injury comorbidities and their therapies are warranted.
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Affiliation(s)
- Reto A Stocker
- Institute for Anesthesiology and Intensive Care Medicine, Klinik Hirslanden, CH-8032 Zurich, Switzerland.
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Abstract
PURPOSE OF REVIEW Neurophysiology is a complex network of cellular, electrical, and vascular systems which function to maximize neuronal functioning and brain performance. The brain exists in a closed system made up of parenchyma, cerebrospinal fluid, and blood with any increase in volume leading to a corresponding decrease in one of the components. Once these compensatory mechanisms are exhausted, there is a precipitous increase in the intracranial pressure leading to decreases in cerebral perfusion and resulting ischemia. The cerebral vasculature has significant control over the total volume of blood and regional flow throughout the brain via autoregulation. Through this process, blood flow is tightly regulated to prevent fluctuations and is coupled precisely with metabolic demand. Moreover, oxygen delivery and aerobic respiration are essential for proper brain functioning and can become deranged in various disease states leading to cellular injury and death. RECENT FINDINGS Ongoing trials have provided evidence that in addition to targeted therapy for intracranial pressure monitoring, optimizing brain tissue oxygenation and cerebral autoregulation may lead to improved clinical outcomes. An understanding of neurophysiology is not only essential for treating patients suffering from intracranial injury but also for the development of novel monitoring and therapeutic techniques.
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Continuous optical monitoring of cerebral hemodynamics during head-of-bed manipulation in brain-injured adults. Neurocrit Care 2015; 20:443-53. [PMID: 23653267 DOI: 10.1007/s12028-013-9849-7] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
INTRODUCTION Head-of-bed manipulation is commonly performed in the neurocritical care unit to optimize cerebral blood flow (CBF), but its effects on CBF are rarely measured. This pilot study employs a novel, non-invasive instrument combining two techniques, diffuse correlation spectroscopy (DCS) for measurement of CBF and near-infrared spectroscopy (NIRS) for measurement of cerebral oxy- and deoxy-hemoglobin concentrations, to monitor patients during head-of-bed lowering. METHODS Ten brain-injured patients and ten control subjects were monitored continuously with DCS and NIRS while the head-of-bed was positioned first at 30° and then at 0°. Relative CBF (rCBF) and concurrent changes in oxy- (ΔHbO2), deoxy- (ΔHb), and total-hemoglobin concentrations (ΔTHC) from left/right frontal cortices were monitored for 5 min at each position. Patient and control response differences were assessed. RESULTS rCBF, ΔHbO2, and ΔTHC responses to head lowering differed significantly between brain-injured patients and healthy controls (P < 0.02). For patients, rCBF changes were heterogeneous, with no net change observed in the group average (0.3 ± 28.2 %, P = 0.938). rCBF increased in controls (18.6 ± 9.4 %, P < 0.001). ΔHbO2, ΔHb, and ΔTHC increased with head lowering in both groups, but to a larger degree in brain-injured patients. rCBF correlated moderately with changes in cerebral perfusion pressure (R = 0.40, P < 0.001), but not intracranial pressure. CONCLUSION DCS/NIRS detected differences in CBF and oxygenation responses of brain-injured patients versus controls during head-of-bed manipulation. This pilot study supports the feasibility of continuous bedside measurement of cerebrovascular hemodynamics with DCS/NIRS and provides the rationale for further investigation in larger cohorts.
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Varsos GV, Kolias AG, Smielewski P, Brady KM, Varsos VG, Hutchinson PJ, Pickard JD, Czosnyka M. A noninvasive estimation of cerebral perfusion pressure using critical closing pressure. J Neurosurg 2015; 123:638-48. [PMID: 25574566 DOI: 10.3171/2014.10.jns14613] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
OBJECT Cerebral blood flow is associated with cerebral perfusion pressure (CPP), which is clinically monitored through arterial blood pressure (ABP) and invasive measurements of intracranial pressure (ICP). Based on critical closing pressure (CrCP), the authors introduce a novel method for a noninvasive estimator of CPP (eCPP). METHODS Data from 280 head-injured patients with ABP, ICP, and transcranial Doppler ultrasonography measurements were retrospectively examined. CrCP was calculated with a noninvasive version of the cerebrovascular impedance method. The eCPP was refined with a predictive regression model of CrCP-based estimation of ICP from known ICP using data from 232 patients, and validated with data from the remaining 48 patients. RESULTS Cohort analysis showed eCPP to be correlated with measured CPP (R = 0.851, p < 0.001), with a mean ± SD difference of 4.02 ± 6.01 mm Hg, and 83.3% of the cases with an estimation error below 10 mm Hg. eCPP accurately predicted low CPP (< 70 mm Hg) with an area under the curve of 0.913 (95% CI 0.883-0.944). When each recording session of a patient was assessed individually, eCPP could predict CPP with a 95% CI of the SD for estimating CPP between multiple recording sessions of 1.89-5.01 mm Hg. CONCLUSIONS Overall, CrCP-based eCPP was strongly correlated with invasive CPP, with sensitivity and specificity for detection of low CPP that show promise for clinical use.
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Affiliation(s)
- Georgios V Varsos
- Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, United Kingdom
| | - Angelos G Kolias
- Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, United Kingdom
| | - Peter Smielewski
- Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, United Kingdom
| | - Ken M Brady
- Baylor College of Medicine, Texas Children's Hospital, Houston, Texas
| | | | - Peter J Hutchinson
- Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, United Kingdom
| | - John D Pickard
- Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, United Kingdom
| | - Marek Czosnyka
- Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, United Kingdom;,Institute of Electronic Systems, Warsaw University of Technology, Warsaw, Poland
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Prabhakar H, Sandhu K, Bhagat H, Durga P, Chawla R. Current concepts of optimal cerebral perfusion pressure in traumatic brain injury. J Anaesthesiol Clin Pharmacol 2014; 30:318-27. [PMID: 25190937 PMCID: PMC4152669 DOI: 10.4103/0970-9185.137260] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
Traumatic brain injury (TBI) consists of varied pathophysiological consequences and alteration of intracranial dynamics, reduction of the cerebral blood flow and oxygenation. In the past decade more emphasis has been directed towards optimizing cerebral perfusion pressure (CPP) in patients who have suffered TBI. Injured brain may show signs of ischemia if CPP remains below 50 mmHg and raising the CPP above 60 mmHg may avoid cerebral oxygen desaturation. Though CPP above 70 mmHg is influential in achieving an improved patient outcome, maintenance of CPP higher than 70 mmHg was associated with greater risk of acute respiratory distress syndrome (ARDS). The target CPP has been laid within 50-70 mmHg. Cerebral blood flow and metabolism are heterogeneous after TBI and with regional temporal differences in the requirement for CPP. Brain monitoring techniques such as jugular venous oximetry, monitoring of brain tissue oxygen tension (PbrO2), and cerebral microdialysis provide complementary and specific information that permits the selection of the optimal CPP. This review highlights the rationale for use CPP directed therapies and neuromonitoring to identify optimal CPP of head injured patients. The article also reviews the evidence provided by various clinical trials regarding optimal CPP and their application in the management of head injured patients.
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Affiliation(s)
- Hemanshu Prabhakar
- Department of Neuroanaesthesiology, Neurosciences Centre, All India Institute of Medical Sciences, PGIMER, Chandigarh, India
| | - Kavita Sandhu
- Department of Neuroanaesthesiology and Critical Care, Max Superspeciality Hospital, PGIMER, Chandigarh, India
| | - Hemant Bhagat
- Department of Anaesthesia and Intensive Care, PGIMER, Chandigarh, India
| | - Padmaja Durga
- Department of Anesthesiology and Intensive Care, Nizam's Institute of Medical Sciences, Hyderabad, India
| | - Rajiv Chawla
- Department of Anaesthesiology and Intensive Care, G B Pant Hospital, New Delhi, India
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Griesdale DEG, Örtenwall V, Norena M, Wong H, Sekhon MS, Kolmodin L, Henderson WR, Dodek P. Adherence to guidelines for management of cerebral perfusion pressure and outcome in patients who have severe traumatic brain injury. J Crit Care 2014; 30:111-5. [PMID: 25179411 DOI: 10.1016/j.jcrc.2014.07.026] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2014] [Revised: 07/23/2014] [Accepted: 07/25/2014] [Indexed: 11/17/2022]
Abstract
PURPOSE The aims of this study are to assess adherence to the Brain Trauma Foundation (BTF) cerebral perfusion pressure (CPP) guidelines and to determine if adherence is associated with mortality in patients who have a severe traumatic brain injury. MATERIALS AND METHODS Retrospective cohort study of 127 patients admitted to one intensive care unit between 2006 and 2012. Adherence to BTF guidelines was measured as the time that the CPP was within 50 to 70 mm Hg divided by the total time of CPP monitoring (CPP time index). RESULTS The percentage of time that the CPP was within the recommended range was 31.6% (SD, 22.2); CPP was greater than 70 mm Hg for 63.9% (SD, 26.2) of the time and less than 50 mm Hg for 4.5% of the time (SD, 16.3). After adjustment for covariates, CPP time index (between 50 and 70 mm Hg) was not associated with hospital mortality (odds ratio [OR], 1.2; 95% confidence interval [CI], 0.98-1.6; P= .079). The time indices for CPP ≥70 and <50 mm Hg were associated with decreased (OR, 0.66; 95%CI, 0.52-0.82; P< .0001) and increased (OR, 9.9; 95% CI, 1.4-69.6; P= .021) mortality, respectively. CONCLUSION Cerebral perfusion pressure was greater than 70 mm Hg for most of the time. This level of CPP was associated with decreased hospital mortality.
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Affiliation(s)
- Donald E G Griesdale
- Division of Critical Care Medicine, Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada; Department of Anesthesiology, Pharmacology and Therapeutics University of British Columbia, Vancouver, British Columbia, Canada; Centre for Clinical Epidemiology and Evaluation, Vancouver Coastal Health Research Institute, Vancouver British Columbia, Canada.
| | - Victoria Örtenwall
- Department of Anaesthesiology and Critical Care Medicine, Lund University, Lund, Sweden
| | - Monica Norena
- Centre for Health Evaluation & Outcome Sciences, Providence Health Care and University of British Columbia, Vancouver, British Columbia, Canada
| | - Hubert Wong
- Centre for Health Evaluation & Outcome Sciences, Providence Health Care and University of British Columbia, Vancouver, British Columbia, Canada; School of Population and Public Health, University of British Columbia, Vancouver, British Columbia, Canada
| | - Mypinder S Sekhon
- Division of Critical Care Medicine, Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - Leif Kolmodin
- Division of Critical Care Medicine, Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - William R Henderson
- Division of Critical Care Medicine, Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - Peter Dodek
- Division of Critical Care Medicine, Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada; Centre for Health Evaluation & Outcome Sciences, Providence Health Care and University of British Columbia, Vancouver, British Columbia, Canada
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Le Roux P. Physiological monitoring of the severe traumatic brain injury patient in the intensive care unit. Curr Neurol Neurosci Rep 2013; 13:331. [PMID: 23328942 DOI: 10.1007/s11910-012-0331-2] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Traumatic brain injury (TBI) is a major cause of morbidity and mortality worldwide. Despite encouraging animal research, pharmacological agents and neuroprotectants have disappointed in the clinical environment. Current TBI management therefore is directed towards identification, prevention, and treatment of secondary cerebral insults that are known to exacerbate outcome after injury. This strategy is based on a variety of monitoring techniques that include the neurological examination, imaging, laboratory analysis, and physiological monitoring of the brain and other organ systems used to guide therapeutic interventions. Recent clinical series suggest that TBI management informed by multimodality monitoring is associated with improved patient outcome, in part because care is provided in a patient-specific manner. In this review we discuss physiological monitoring of the brain after TBI and the emerging field of neurocritical care bioinformatics.
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Affiliation(s)
- Peter Le Roux
- Department of Neurosurgery, University of Pennsylvania, 235 South 8th Street, Philadelphia, PA 19106, USA.
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El Ahmadieh TY, Adel JG, El Tecle NE, Daou MR, Aoun SG, Nanney AD, Bendok BR. Surgical treatment of elevated intracranial pressure: decompressive craniectomy and intracranial pressure monitoring. Neurosurg Clin N Am 2013; 24:375-91. [PMID: 23809032 DOI: 10.1016/j.nec.2013.03.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Surgical techniques that address elevated intracranial pressure include (1) intraventricular catheter insertion and cerebrospinal fluid drainage, (2) removal of an intracranial space-occupying lesion, and (3) decompressive craniectomy. This review discusses the role of surgery in the management of elevated intracranial pressure, with special focus on intraventricular catheter placement and decompressive craniectomy. The techniques and potential complications of each procedure are described, and the existing evidence regarding the impact of these procedures on patient outcome is reviewed. Surgical management of mass lesions and ischemic or hemorrhagic stroke occurring in the posterior fossa is not discussed herein.
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Affiliation(s)
- Tarek Y El Ahmadieh
- Department of Neurological Surgery, McGaw Medical Center, Northwestern University Feinberg School of Medicine, 676 North Saint Clair Street, Suite 2210, Chicago, IL 60611, USA
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Abstract
OBJECTIVE To review novel techniques of noninvasive brain stimulation (NBS), which may have value in assessment and treatment of traumatic brain injury (TBI). METHODS Review of the following techniques: transcranial magnetic stimulation, transcranial direct current stimulation, low-level laser therapy, and transcranial Doppler sonography. Furthermore, we provide a brief overview of TMS studies to date. MAIN FINDINGS We describe the rationale for the use of these techniques in TBI, discuss their possible mechanisms of action, and raise a number of considerations relevant to translation of these methods to clinical use. Depending on the stimulation parameters, NBS may enable suppression of the acute glutamatergic hyperexcitability following TBI and/or counter the excessive GABAergic effects in the subacute stage. In the chronic stage, brain stimulation coupled to rehabilitation may enhance behavioral recovery, learning of new skills, and cortical plasticity. Correlative animal models and comprehensive safety trials seem critical to establish the use of these modalities in TBI. CONCLUSIONS Different forms of NBS techniques harbor the promise of diagnostic and therapeutic utility, particularly to guide processes of cortical reorganization and enable functional restoration in TBI. Future lines of safety research and well-designed clinical trials in TBI are warranted to determine the capability of NBS to promote recovery and minimize disability.
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Abstract
INTRODUCTION Pressure-reactivity index (PRx) is a useful tool in brain monitoring of trauma patients, but the question remains about its critical values. Using our TBI database, we identified the thresholds for PRx and other monitored parameters that maximize the statistical difference between death/survival and favorable/unfavorable outcomes. We also investigated how these thresholds depend on clinical factors such as age, gender and initial GCS. METHODS A total of 459 patients from our database were eligible. Tables of 2 × 2 format were created grouping patients according to survival/death or favorable/unfavorable outcomes and varying thresholds for PRx, ICP and CPP. Pearson's chi square was calculated, and the thresholds returning the highest score were assumed to have the best discriminative value. The same procedure was repeated after division according to clinical factors. RESULTS In all patients, we found that PRx had different thresholds for survival (0.25) and for favorable outcome (0.05). Thresholds of 70 mmHg for CPP and 22 mmHg for ICP were identified for both survival and favorable outcomes. The ICP threshold for favorable outcome was lower (18 mmHg) in females and patients older than 55 years. In logistic regression models, independent variables associating with mortality and unfavorable outcome were age, GCS, ICP and PRx. CONCLUSION The prognostic role of PRx is confirmed but with a lower threshold of 0.05 for favorable outcome than for survival (0.25). Results for ICP are in line with current guidelines. However, the lower value in elderly and in females suggests increased vulnerability to intracranial hypertension in these groups.
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Abstract
The gold standard for assessing neurological function is the bedside clinical examination. However, in neurocritical patients, the signs and symptoms related to the severity of illness can often be ambiguous. It can be hard to distinguish between a severe but stable disease state and one that is dynamic and in a critical decline. Clinicians and family members alike may struggle with the uncertainty of functional outcome prediction. Intermediate biomarkers of brain injury can assist with ongoing clinical management of patients, and in some circumstances can guide prognosis. Used in the right setting, biomarkers in neurocritical care can also aid with decisions to intensify treatment or avoid prolonged and unnecessary therapy. The term biomarker is used in various ways, and here we use it to refer to 3 general types: 1) circulating blood macromolecules, 2) brain imaging, and 3) continuous invasive monitors. Despite its promise, biomarkers have several limitations and should be interpreted in the context of the overall clinical assessment.
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Affiliation(s)
- W Taylor Kimberly
- Department of Neurology, Division of Neurocritical Care and Emergency Neurology, Massachusetts General Hospital, Boston, MA 02114, USA.
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Effects of cerebrovascular pressure reactivity-guided optimization of cerebral perfusion pressure on brain tissue oxygenation after traumatic brain injury. Crit Care Med 2010; 38:1343-7. [PMID: 20154598 DOI: 10.1097/ccm.0b013e3181d45530] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
OBJECTIVE To evaluate the concept of a cerebrovascular pressure reactivity-guided optimal cerebral perfusion pressure after traumatic brain injury by analyzing the relationship between optimal cerebral perfusion pressure and brain tissue oxygen. DESIGN Prospective observational cohort study. SETTING Neurosurgical intensive care unit of a university hospital. PATIENTS Thirty-eight patients after head injury. INTERVENTIONS Continuous computerized monitoring of mean arterial pressure, intracranial pressure, and brain tissue oxygen for 5.3 +/- 2.6 days. The index of cerebrovascular pressure reactivity was calculated as a moving correlation coefficient between spontaneous low-frequency fluctuations of mean arterial pressure and intracranial pressure. Optimal cerebral perfusion pressure was defined as the cerebral perfusion pressure level with the lowest average index of cerebrovascular pressure reactivity. MEASUREMENTS AND MAIN RESULTS Optimal cerebral perfusion pressure could be identified in 32 of 38 patients. Median optimal cerebral perfusion pressure was between 70 and 75 mm Hg (range, 60-100 mm Hg). Below the level of optimal cerebral perfusion pressure, brain tissue oxygen decreased in parallel to cerebral perfusion pressure, whereas brain tissue oxygen reached a plateau above optimal cerebral perfusion pressure. Optimal cerebral perfusion pressure correlated significantly with the cerebral perfusion pressure level, where brain tissue oxygen reached its plateau (r = .79; p < .01). Average brain tissue oxygen at optimal cerebral perfusion pressure was 24.5 +/- 6.0 mm Hg. CONCLUSIONS This study supports the concept of cerebrovascular pressure reactivity-based individual optimal cerebral perfusion pressure. Driving cerebral perfusion pressure in excess of optimal cerebral perfusion pressure does not yield improvements in brain tissue oxygen after head injury and should be avoided, whereas cerebral perfusion pressure below optimal cerebral perfusion pressure may result in secondary cerebral ischemia.
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Abstract
PURPOSE OF REVIEW This review highlights recent advances in cerebral microdialysis for investigational and clinical neurochemical monitoring in patients with critical neurological conditions. RECENT FINDINGS Use of microdialysis with other methods, including PET, electrophysiological monitoring and brain tissue oximetry in traumatic brain injury, subarachnoid hemorrhage with vasospasm, and infarction with refractory increased intracranial pressure have been reported. Potentially adverse neurochemical effects of nonconvulsive status epilepticus and cortical slow depolarization waves, both of which are increasingly recognized in traumatic brain injury and stroke patients, have been reported. The explosive growth in the use of cerebral oximetry with targeted management of brain tissue oxygen levels is leading to greater understanding of derangements of cerebral bioenergetics in the critically ill brain, but there remain unresolved basic issues. Understanding of the analytes that are measurable at the bedside - glucose, lactate, pyruvate, glutamate and glycerol - continues to evolve with glucose, lactate, pyruvate and the lactate-pyruvate ratio taking center stage. Analytes including inflammatory biomarkers such as cytokines and metabolites of nitric oxide are presently investigational, but hold promise for future application in advancing our understanding of basic pathophysiology, therapeutic target selection and prognostication. Growing consensus on indications for use of clinical microdialysis and advances in commercially available equipment continue to make microdialysis increasingly 'ready for prime time.' SUMMARY Cerebral microdialysis is an established tool for neurochemical research in the ICU. This technique cannot be fruitfully used in isolation, but when combined with other monitoring methods provides unique insights into the biochemical and physiological derangements in the injured brain.
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Effects of autoregulation and CO2 reactivity on cerebral oxygen transport. Ann Biomed Eng 2009; 37:2288-98. [PMID: 19629692 DOI: 10.1007/s10439-009-9763-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2009] [Accepted: 07/15/2009] [Indexed: 10/20/2022]
Abstract
Both autoregulation and CO(2) reactivity are known to have significant effects on cerebral blood flow and thus on the transport of oxygen through the vasculature. In this paper, a previous model of the autoregulation of blood flow in the cerebral vasculature is expanded to include the dynamic behavior of oxygen transport through binding with hemoglobin. The model is used to predict the transfer functions for both oxyhemoglobin and deoxyhemoglobin in response to fluctuations in arterial blood pressure and arterial CO(2) concentration. It is shown that only six additional nondimensional groups are required in addition to the five that were previously found to characterize the cerebral blood flow response. A resonant frequency in the pressure-oxyhemoglobin transfer function is found to occur in the region of 0.1 Hz, which is a frequency of considerable physiological interest. The model predictions are compared with results from the published literature of phase angle at this frequency, showing that the effects of changes in breathing rate can significantly alter the inferred phase dynamics between blood pressure and hemoglobin. The question of whether dynamic cerebral autoregulation is affected under conditions of stenosis or stroke is then examined.
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An analysis of regional microvascular loss and recovery following two grades of fluid percussion trauma: a role for hypoxia-inducible factors in traumatic brain injury. J Cereb Blood Flow Metab 2009; 29:575-84. [PMID: 19088740 DOI: 10.1038/jcbfm.2008.151] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Secondary hypoxic/ischemic injuries, stemming from reductions in cerebral blood flow are important contributing factors in progressive neuronal dysfunction after brain trauma. A greater preclinical understanding of how brain trauma leads to secondary hypoxia/ischemia is necessary in the development of posttraumatic brain injury (TBI) therapeutics. To this end, we examined the density of microvascular coverage in the injured and contralateral cortical hemispheres using two intensities of fluid percussion trauma in rats. A silicone microangiography technique showed a significant loss in microvascular density in 2 atmosphere (atm) (16.9+/-3.8%) and 3 atm (15.7+/-1.3%) injured animals relative to sham animals (29.9+/-2.5%; P<0.01). RECA-1 immunohistochemistry indicated that capillary changes involved a reduction in capillary number and diameter. Reduction in microvascular density was shown to be a diffuse phenomenon occurring up to 4 mm rostral and caudal to the injury epicenter. Recovery of microvasculature occurred by 2 weeks after injury only in the 2 atm injury group. Expression of HIF1alpha and increased vascular endothelial growth factor expression were observed in the ipsilateral hippocampus suggesting sufficiently impaired microcirculation resulting in the expression of hypoxic-response proteins. Collectively, the results indicate diffuse and heterogeneous microvascular alterations as well as endogenous expression of neuroprotective and neovascularization pathways after TBI.
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Abstract
Head injury remains a major cause of preventable death and serious morbidity in young adults. Based on the available evidence, it appears that a cerebral perfusion pressure of 50 to 70 mm Hg is generally adequate to ensure cerebral oxygen delivery and prevent ischemia. However, evidence suggests that perfusion requirements may not only vary across the injured brain but also differ depending on the time since injury. Such heterogeneity, both within and between subjects, suggests that individualized therapy may be an appropriate treatment strategy. Future studies should aim to assess which groups of patients, and what regional pathophysiological derangements, may benefit with improvements in functional outcome from therapeutic increases or decreases in cerebral perfusion pressure beyond these proposed limits. Such functional improvements may be of immense importance to patients and require formal neurocognitive assessments to discriminate improvements.
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Affiliation(s)
- Monica Trivedi
- Division of Anaesthesia, University of Cambridge, Addenbrooke's Hospital, Cambridge, United Kingdom
| | - Jonathan P. Coles
- Wolfson Brain Imaging Centre, Department of Clinical Neurosciences, University of Cambridge, Addenbrooke's Hospital, Cambridge, United Kingdom, Division of Anaesthesia, University of Cambridge, Addenbrooke's Hospital, Cambridge, United Kingdom,
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Timaru-Kast R, Meissner A, Heimann A, Hoelper B, Kempski O, Alessandri B. Acute subdural hematoma in pigs: role of volume on multiparametric neuromonitoring and histology. J Neurotrauma 2008; 25:1107-19. [PMID: 18771396 DOI: 10.1089/neu.2008.0517] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Traumatic brain injury (TBI) is often complicated by acute subdural hemorrhage (ASDH) with a high mortality rate. The pathophysiological mechanisms behind such an injury type and the contribution of blood to the extent of an injury remain poorly understood. Therefore, the goals of this study were to establish a porcine ASDH model in order to investigate pathomechanisms of ASDH and to compare effects induced by blood or sheer volume. Thus, we infused 2, 5, and 9 mL of blood (up to 15% of intracranial volume), and we compared a 5-mL blood and paraffin oil volume to separate out effects of extravasated blood on brain tissue. An extended neuromonitoring was applied that lasted up to 12 h after injury and included intracranial pressure (ICP), cerebral perfusion pressure (CPP), tissue oxygen concentration (ptiO(2)), biochemical markers (glutamate, lactate), somatosensory evoked potentials (SEP), brain water content, and histological assessment (Lesion Index [LI]). Volume-dependent changes were detected mainly during the first hours after injury. ICP increased to significant levels (p < 0.05) of 36.89 +/- 1.59, 15.52 +/- 0.48, and 11.25 +/- 0.35 mm Hg after 9, 5, and 2 mL of subdural blood, respectively (sham, 4.85 +/- 0.06 mm Hg). The ptiO(2) dropped drastically after 9 mL of subdural blood without recovery in both hemispheres to below 20% of baseline, but was affected little after 2 and 5 mL in the acute monitoring period (maximal drop to 71% of baseline). Later, 5 mL of blood led to a significant increase of ptiO(2) compared to 2 mL ipsilaterally (p < 0.05). Glutamate and lactate showed a comparable pattern with a long-lasting increase after 9 mL of blood and short-lasting changes after 2 and 5 mL. The two smaller volumes caused an increased brain swelling (2 mL, 80.60 +/- 0.34%; 5 mL, 81.20 +/- 0.66%; p < 0.05 vs. sham), a significant LI (sham, 6.4 +/- 1.4; 2 mL, 30.0 +/- 0.95; 5 mL, 32.1 +/- 1.2; p < 0.05 vs. sham), and a reduced SEP amplitude (5 mL, p < 0.05 vs. baseline) at the end of the experiment. A 9-mL led to herniation during the experiment causing dramatical brain swelling and acute histological damage. Comparison of blood volume with paraffin oil showed no significance, indicating that volume alone determines the acute pathophysiological processes leading to a rapidly developing histological damage. Additional effects due to blood contact with brain tissue (e.g., inflammation) may be detected only at later time points (>12 h).
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Affiliation(s)
- Ralph Timaru-Kast
- Institute for Neurosurgical Pathophysiology, Johannes Gutenberg University, Mainz, Germany
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20
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Abstract
Multimodality monitoring of cerebral physiology encompasses the application of different monitoring techniques and integration of several measured physiologic and biochemical variables into assessment of brain metabolism, structure, perfusion, and oxygenation status. Novel monitoring techniques include transcranial Doppler ultrasonography, neuroimaging, intracranial pressure, cerebral perfusion, and cerebral blood flow monitors, brain tissue oxygen tension monitoring, microdialysis, evoked potentials, and continuous electroencephalogram. Multimodality monitoring enables immediate detection and prevention of acute neurologic injury as well as appropriate intervention based on patients' individual disease states in the neurocritical care unit. Real-time analysis of cerebral physiologic, metabolic, and cardiovascular parameters simultaneously has broadened knowledge about complex brain pathophysiology and cerebral hemodynamics. Integration of this information allows for more precise diagnosis and optimization of management of patients with brain injury.
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Affiliation(s)
- Katja Elfriede Wartenberg
- Neurological Intensive Care Unit, New York Presbyterian Hospital, Columbia University Medical Center, 710 W. 168th Street, New York, NY 10032, USA
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21
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Abstract
Increased intracranial pressure (ICP) is an important cause of secondary brain injury, and ICP monitoring has become an established component of brain monitoring after traumatic brain injury. ICP cannot be reliably estimated from any specific clinical feature or computed tomography finding and must actually be measured. Different methods of monitoring ICP have been described but intraventricular catheters and microtransducer systems are most widely used in clinical practice. ICP is a complex variable that links ICP and cerebral perfusion pressure and provides additional information from identification and analysis of pathologic ICP wave forms. ICP monitoring can also be augmented by measurement of indices describing cerebrovascular pressure reactivity and pressure-volume compensatory reserve. There is considerable variability in the use of ICP monitoring and treatment modalities among head injury centers. However, there is a large body of clinical evidence supporting the use of ICP monitoring to detect intracranial mass lesions early, guide therapeutic interventions, and assess prognosis, and it is recommended by consensus guidelines for head injury management. There remains a need for a prospective, randomized, controlled trial to identify the value of ICP monitoring and management after head injury.
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Affiliation(s)
- Martin Smith
- National Hospital for Neurology and Neurosurgery, University College London Hospitals NHS Trust, London, UK.
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22
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Bader MK. Recognizing and treating ischemic insults to the brain: the role of brain tissue oxygen monitoring. Crit Care Nurs Clin North Am 2006; 18:243-56, xi. [PMID: 16728310 DOI: 10.1016/j.ccell.2006.01.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
This article describes the potential application of brain tissue oxygen monitoring technology in the care of patients who have sustained traumatic brain injury (TBI) or subarachnoid hemorrhage (SAH). To accomplish this objective, a review of the intracranial dynamics that are created by primary and secondary brain injury, and the challenges of optimizing oxygen delivery to the injured brain are presented. Furthermore, interventions that facilitate cerebral oxygen supply and reduce oxygen consumption are identified. Finally, application of this technology is highlighted by using case vignettes of patients who have TBI or SAH.
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Affiliation(s)
- Mary Kay Bader
- Mission Hospital, 27700 Medical Center Road, Mission Viejo, CA 92691, USA.
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23
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Abstract
Multimodality monitoring of cerebral physiology encompasses the application of different monitoring techniques and integration of several measured physiological and biochemical variables into the assessment of brain metabolism, structure, perfusion and oxygenation status, in addition to clinical evaluation. Novel monitoring techniques include transcranial Doppler ultrasonography, neuroimaging, intracranial pressure, cerebral perfusion and cerebral blood flow monitors, brain tissue oxygen tension monitoring, microdialysis, evoked potentials and continuous electroencephalography. Multimodality monitoring enables the immediate detection and prevention of acute neurological events, as well as appropriate intervention based on a patient’s individual disease state in the neurocritical care unit. Simultaneous real-time analysis of cerebral physiological, metabolic and cardiovascular parameters has broadened knowledge regarding complex brain pathophysiology and cerebral hemodynamics. Integration of this information allows for a more precise diagnosis and optimization of management of patients with brain injury.
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Affiliation(s)
- Katja Elfriede Wartenberg
- Columbia University, Division of Stroke and Critical Care, Neurological Institute, 710 West 168th Street, NY 10032, USA
| | - J Michael Schmidt
- Columbia University, Division of Stroke and Critical Care, Neurological Institute, 710 W, 168th Street, NY 10032, USA
| | - Derk W Krieger
- Cleveland Clinic Foundation, Section of Stroke and Neurologic Intensive Care, Department of Neurology, S91, 9500 Euclid Avenue, OH 44195, USA
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24
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Payne SJ, Tarassenko L. Combined transfer function analysis and modelling of cerebral autoregulation. Ann Biomed Eng 2006; 34:847-58. [PMID: 16708269 DOI: 10.1007/s10439-006-9114-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2005] [Accepted: 03/15/2006] [Indexed: 10/24/2022]
Abstract
The clinical importance of cerebral autoregulation has resulted in a significant body of literature that attempts both to model the underlying physiological processes and to estimate the mathematical relationships between clinically measurable variables, the most common of which are Arterial Blood Pressure and Cerebral Blood Flow Velocity. These approaches have, however, rarely been used together to interpret clinical data. A simple model of cerebral autoregulation is thus proposed here, based on a flow dependent feedback mechanism with gain and time constant that adjusts arterial compliance. Analysis of this model shows that it closely approximates a second order system for typical values of physiological parameters. The model parameters can be optimally estimated from available experimental data for the Impulse Response (IR), yielding physiologically reasonable values, although there is one free parameter that must be fixed. The effects of changes in feedback gain and time constant are found to be significant on the predicted IR and can thus be estimated robustly from experimental data. The effects of elevated baseline Intracranial Pressure (ICP) are found to be exactly equivalent to a reduced feedback gain, although the solution is much less sensitive to the former effect. A transfer function approach can be used to estimate autoregulation status clinically using a physiologically-based model, thus providing greater insight into the processes that govern cerebral autoregulation.
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Affiliation(s)
- S J Payne
- Department of Engineering Science, University of Oxford, Parks Road, OX1 3PJ, Oxford, UK
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25
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Bader MK, Arbour R, Palmer S. Refractory increased intracranial pressure in severe traumatic brain injury: barbiturate coma and bispectral index monitoring. ACTA ACUST UNITED AC 2006; 16:526-41. [PMID: 16269897 DOI: 10.1097/00044067-200510000-00009] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Patients with severe traumatic brain injury resulting in increased intracranial pressure refractory to first-tier interventions challenge the critical care team. After exhausting these initial interventions, critical care practitioners may utilize barbiturate-induced coma in an attempt to reduce the intracranial pressure. Titrating appropriate levels of barbiturate is imperative. Underdosing the drug may fail to control the intracranial pressure, whereas overdosing may lead to untoward effects such as hypotension and cardiac compromise. Monitoring for a therapeutic level of barbiturate coma includes targeting drug levels and using continuous electroencephalogram monitoring, considered the gold standard. New technology, the Bispectral Index monitor, utilizes electroencephalogram principles to monitor the level of sedation and hypnosis in the critical care environment. This technology is now being considered for targeting appropriate levels of barbiturate coma.
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Bodo M, Pearce FJ, Baranyi L, Armonda RA. Changes in the intracranial rheoencephalogram at lower limit of cerebral blood flow autoregulation. Physiol Meas 2005; 26:S1-17. [PMID: 15798222 DOI: 10.1088/0967-3334/26/2/001] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Cerebral blood flow (CBF) reactivity monitoring is an appropriate primary parameter to evaluate cerebral resuscitation due to a systemic or regional cerebral injury leading to possible irreversible brain injury. Use of the electrical impedance method to estimate CBF is rare, as the method's anatomical background is not well understood. Use of intracranial rheoencephalography (iREG) during hemorrhage and comparison of iREG to other CBF measurements have not been previously reported. Our hypothesis was that iREG would reflect early cerebrovascular alteration (CBF autoregulation). Studies comparing iREG, laser Doppler flowmetry and ultrasound were undertaken on anesthetized rats to define CBF changes during hemorrhage. Blood was removed at a rate required to achieve a mean arterial blood pressure (MABP) of 40 mm Hg over 15 min. Estimation of CBF was taken with intracranial, bipolar REG (REG I; n=14), laser Doppler flowmetry (LDF; n=3) and carotid flow by ultrasound (n=11). Data were processed off-line. During the initial phase of hemorrhage, when MABP was close to 40 mm Hg, intracranial REG amplitude transiently increased (80.94%); LDF (77.92%) and carotid flow (52.04%) decreased and changed with systemic arterial pressure. Intracranial REG amplitude change suggests classical CBF autoregulation, demonstrating its close relationship to arteriolar changes. The studies indicate that iREG might reflect cerebrovascular responses more accurately than changes in local CBF measured by LDF and carotid flow. REG may indicate promise as a continuous, non-invasive life-sign monitoring tool with potential advantages over ultrasound, the CBF measurement technique normally applied in clinical practice. REG has particular advantages in non-hospital settings such as military and emergency medicine.
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Affiliation(s)
- M Bodo
- Department of Resuscitative Medicine, Walter Reed Army Institute of Research, Silver Spring, MD 20910, USA.
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27
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Raz A, Lieber B, Soliman F, Buhle J, Posner J, Peterson BS, Posner MI. Ecological nuances in functional magnetic resonance imaging (fMRI): psychological stressors, posture, and hydrostatics. Neuroimage 2005; 25:1-7. [PMID: 15734338 DOI: 10.1016/j.neuroimage.2004.11.015] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2004] [Revised: 11/09/2004] [Accepted: 11/10/2004] [Indexed: 11/22/2022] Open
Abstract
Brain imaging techniques such as functional magnetic resonance imaging (fMRI) have forged an impressive link between psychology and neuroscience. Whereas most experiments in cognitive psychology require participants to perform while sitting upright in front of display devices, fMRI obliges participants to perform cognitive tasks while lying supine and motionless inside a narrow bore. In addition to introducing psychological and physical stressors, such as loud thumps and head restraints, fMRI procedures also alter brain hydrostatics. The ecological factors associated with current fMRI technology, such as supine posture, may skew cognitive processing and influence hemodynamic and electrophysiological measurements, especially in extreme age groups and pathological populations. Recognizing the central role of fMRI in unraveling the neural mechanisms of cognition, we outline ways to address these limitations.
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Affiliation(s)
- Amir Raz
- MRI Unit, Department of Psychiatry, Columbia University College of Physicians and Surgeons, New York State Psychiatric Institute, 1051 Riverside Drive, Box 74, New York, NY 10032, USA.
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