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The Role of Transcranial Doppler as a Monitoring Tool in the Neurocritical Care Unit. Neurocrit Care 2019. [DOI: 10.1017/9781107587908.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Unnerbäck M, Bloomfield EL, Söderström S, Reinstrup P. The intracranial pressure curve correlates to the pulsatile component of cerebral blood flow. J Clin Monit Comput 2018; 33:77-83. [PMID: 29549499 PMCID: PMC6315053 DOI: 10.1007/s10877-018-0129-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2017] [Accepted: 03/13/2018] [Indexed: 12/02/2022]
Abstract
Current methods to measure cerebral blood flow (CBF) in the neuro critical care setting cannot monitor the CBF continuously. In contrast, continuous measurement of intracranial pressure (ICP) is readily accomplished, and there is a component of ICP that correlates with arterial inflow of blood into the cranial cavity. This property may have utility in using continuous ICP curve analysis to continuously estimate CBF. We examined the data from 13 patients, monitored with an intraventricular ICP device determining the pulsatile amplitude ICPamp as well as the area under the ICP curve (AUCICP). Using an elastance measurement, the ICP curve was converted to craniospinal volume (AUCΔV). The patients were examined with Phase Contrast Magnetic Resonance Imaging (MRI), measuring flow in the carotid and vertebral arteries. This made it possible to calculate CBF for one cardiac cycle (ccCBFMRtot) and divide it into the pulsatile (ccCBFMRpuls) and non-pulsatile (ccCBFMRconst) flow. ICP derived data and MRI measurements were compared. Linear regression was used to establish wellness of fit and ANOVA was used to calculate the P value. No correlation was found between ICPamp and the ccICPMRpuls (P = 0.067). In contrast there was a correlation between the AUCICP and ccCBFMRpuls (R2 = 0.440 P = 0.013). The AUCΔV correlated more appropriately with the ccCBFMRpuls. (R2 = 0.688 P < 0.001). Our findings suggests that the pulsatile part of the intracranial pressure curve, especially when transformed into a volume curve, correlates to the pulsatile part of the CBF.
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Affiliation(s)
- Mårten Unnerbäck
- Department of Clinical Sciences Lund, Intensive Care and Perioperative Medicine, Lund University, Skane University Hospital, Malmö, Sweden. .,IPV SUS Malmö, Inga Marie Nilssons gata 47, 205 02, Malmö, Sweden.
| | | | - Sven Söderström
- Department of Clinical Sciences Lund, Neurosurgery, Lund University, Skane University Hospital, Lund, Sweden
| | - Peter Reinstrup
- Department of Clinical Sciences Lund, Neurosurgery, Lund University, Skane University Hospital, Lund, Sweden
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Donnelly J, Budohoski KP, Smielewski P, Czosnyka M. Regulation of the cerebral circulation: bedside assessment and clinical implications. Crit Care 2016; 20:129. [PMID: 27145751 PMCID: PMC4857376 DOI: 10.1186/s13054-016-1293-6] [Citation(s) in RCA: 122] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Regulation of the cerebral circulation relies on the complex interplay between cardiovascular, respiratory, and neural physiology. In health, these physiologic systems act to maintain an adequate cerebral blood flow (CBF) through modulation of hydrodynamic parameters; the resistance of cerebral vessels, and the arterial, intracranial, and venous pressures. In critical illness, however, one or more of these parameters can be compromised, raising the possibility of disturbed CBF regulation and its pathophysiologic sequelae. Rigorous assessment of the cerebral circulation requires not only measuring CBF and its hydrodynamic determinants but also assessing the stability of CBF in response to changes in arterial pressure (cerebral autoregulation), the reactivity of CBF to a vasodilator (carbon dioxide reactivity, for example), and the dynamic regulation of arterial pressure (baroreceptor sensitivity). Ideally, cerebral circulation monitors in critical care should be continuous, physically robust, allow for both regional and global CBF assessment, and be conducive to application at the bedside. Regulation of the cerebral circulation is impaired not only in primary neurologic conditions that affect the vasculature such as subarachnoid haemorrhage and stroke, but also in conditions that affect the regulation of intracranial pressure (such as traumatic brain injury and hydrocephalus) or arterial blood pressure (sepsis or cardiac dysfunction). Importantly, this impairment is often associated with poor patient outcome. At present, assessment of the cerebral circulation is primarily used as a research tool to elucidate pathophysiology or prognosis. However, when combined with other physiologic signals and online analytical techniques, cerebral circulation monitoring has the appealing potential to not only prognosticate patients, but also direct critical care management.
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Affiliation(s)
- Joseph Donnelly
- />Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, Cambridge Biomedical Campus, University of Cambridge, Hills Road, Cambridge, CB2 0QQ UK
| | - Karol P. Budohoski
- />Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, Cambridge Biomedical Campus, University of Cambridge, Hills Road, Cambridge, CB2 0QQ UK
| | - Peter Smielewski
- />Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, Cambridge Biomedical Campus, University of Cambridge, Hills Road, Cambridge, CB2 0QQ UK
| | - Marek Czosnyka
- />Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, Cambridge Biomedical Campus, University of Cambridge, Hills Road, Cambridge, CB2 0QQ UK
- />Institute of Electronic Systems, Warsaw University of Technology, ul. Nowowiejska 15/19, 00-665 Warsaw, Poland
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Cerebral blood flow and transcranial doppler sonography measurements of CO2-reactivity in acute traumatic brain injured patients. Neurocrit Care 2015; 20:54-9. [PMID: 22700360 DOI: 10.1007/s12028-012-9727-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
BACKGROUND Cerebral blood flow (CBF) measurements are helpful in managing patients with traumatic brain injury (TBI), and testing the cerebrovascular reactivity to CO(2) provides information about injury severity and outcome. The complexity and potential hazard of performing CBF measurements limits routine clinical use. An alternative approach is to measure the CBF velocity using bedside, non-invasive, and transcranial Doppler (TCD) sonography. This study was performed to investigate if TCD is a useful alternative to CBF in patients with severe TBI. METHOD CBF and TCD flow velocity measurements and cerebrovascular reactivity to hypocapnia were simultaneously evaluated in 27 patients with acute TBI. Measurements were performed preoperatively during controlled normocapnia and hypocapnia in patients scheduled for hematoma evacuation under general anesthesia. MAIN FINDING AND CONCLUSION Although the lack of statistical correlation between the calculated reactivity indices, there was a significant decrease in TCD-mean flow velocity and a decrease in CBF with hypocapnia. CBF and TCD do not seem to be directly interchangeable in determining CO(2)-reactivity in TBI, despite both methods demonstrating deviation in the same direction during hypocapnia. TCD and CBF measurements both provide useful information on cerebrovascular events which, although not interchangeable, may complement each other in clinical scenarios.
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Rostami E, Engquist H, Enblad P. Imaging of cerebral blood flow in patients with severe traumatic brain injury in the neurointensive care. Front Neurol 2014; 5:114. [PMID: 25071702 PMCID: PMC4083561 DOI: 10.3389/fneur.2014.00114] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2014] [Accepted: 06/16/2014] [Indexed: 12/21/2022] Open
Abstract
Ischemia is a common and deleterious secondary injury following traumatic brain injury (TBI). A great challenge for the treatment of TBI patients in the neurointensive care unit (NICU) is to detect early signs of ischemia in order to prevent further advancement and deterioration of the brain tissue. Today, several imaging techniques are available to monitor cerebral blood flow (CBF) in the injured brain such as positron emission tomography (PET), single-photon emission computed tomography, xenon computed tomography (Xenon-CT), perfusion-weighted magnetic resonance imaging (MRI), and CT perfusion scan. An ideal imaging technique would enable continuous non-invasive measurement of blood flow and metabolism across the whole brain. Unfortunately, no current imaging method meets all these criteria. These techniques offer snapshots of the CBF. MRI may also provide some information about the metabolic state of the brain. PET provides images with high resolution and quantitative measurements of CBF and metabolism; however, it is a complex and costly method limited to few TBI centers. All of these methods except mobile Xenon-CT require transfer of TBI patients to the radiological department. Mobile Xenon-CT emerges as a feasible technique to monitor CBF in the NICU, with lower risk of adverse effects. Promising results have been demonstrated with Xenon-CT in predicting outcome in TBI patients. This review covers available imaging methods used to monitor CBF in patients with severe TBI.
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Affiliation(s)
- Elham Rostami
- Section of Neurosurgery, Department of Neuroscience, Uppsala University , Uppsala , Sweden ; Department of Neuroscience, Karolinska Institutet , Stockholm , Sweden
| | - Henrik Engquist
- Department of Surgical Sciences, Anaesthesiology and Intensive Care, Uppsala University , Uppsala , Sweden
| | - Per Enblad
- Section of Neurosurgery, Department of Neuroscience, Uppsala University , Uppsala , Sweden
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Timofeev I, Czosnyka M, Carpenter KLH, Nortje J, Kirkpatrick PJ, Al-Rawi PG, Menon DK, Pickard JD, Gupta AK, Hutchinson PJ. Interaction between brain chemistry and physiology after traumatic brain injury: impact of autoregulation and microdialysis catheter location. J Neurotrauma 2011; 28:849-60. [PMID: 21488707 PMCID: PMC3113421 DOI: 10.1089/neu.2010.1656] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Bedside monitoring of cerebral metabolism in traumatic brain injury (TBI) with microdialysis is gaining wider clinical acceptance. The objective of this study was to examine the relationship between the fundamental physiological neuromonitoring modalities intracranial pressure (ICP), cerebral perfusion pressure (CPP), brain tissue oxygen (P(bt)O(2)), and cerebrovascular pressure reactivity index (PRx), and cerebral chemistry assessed with microdialysis, with particular focus on the lactate/pyruvate (LP) ratio as a marker of energy metabolism. Prospectively collected observational neuromonitoring data from 97 patients with TBI, requiring neurointensive care management and invasive cerebral monitoring, were analyzed. A linear mixed model analysis was used to account for individual patient differences. Perilesional tissue chemistry exhibited a significant independent relationship with ICP, P(bt)O(2) and CPP thresholds, with increasing LP ratio in response to decrease in P(bt)O(2) and CPP, and increase in ICP. The relationship between CPP and chemistry depended upon the state of PRx. Within the studied physiological range, tissue chemistry only changed in response to increasing ICP or drop in P(bt)O(2)<1.33 kPa (10 mmHg). In agreement with previous studies, significantly higher levels of cerebral lactate (p<0.001), glycerol (p=0.013), LP ratio (p<0.001) and lactate/glucose (LG) ratio (p=0.003) were found in perilesional tissue, compared to "normal" brain tissue (Mann-Whitney test). These differences remained significant following adjustment for the influences of other important physiological parameters (ICP, CPP, P(bt)O(2), P(bt)CO(2), PRx, and brain temperature; mixed linear model), suggesting that they may reflect inherent tissue properties related to the initial injury. Despite inherent biochemical differences between less-injured brain and "perilesional" cerebral tissue, both tissue types exhibited relationships between established physiological variables and biochemistry. Decreases in perfusion and oxygenation were associated with deteriorating neurochemistry and these effects were more pronounced in perilesional tissue and when cerebrovascular reactivity was impaired.
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Affiliation(s)
- Ivan Timofeev
- Division of Neurosurgery, University of Cambridge, Addenbrooke's Hospital, Cambridge, United Kingdom.
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Poon WS. Great hospitals of Asia: neurosurgery at Prince of Wales Hospital. World Neurosurg 2011; 75:383-6. [PMID: 21600469 DOI: 10.1016/j.wneu.2011.02.027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2011] [Accepted: 02/08/2011] [Indexed: 10/18/2022]
Abstract
Prince of Wales Hospital, a 1400-bed regional referral center, was established in 1984 as the primary teaching hospital of the second medical school in Hong Kong at the Chinese University of Hong Kong. The Academic Division of Neurosurgery was given an autonomous status, the support of 40 acute beds, and a well-equipped and well-staffed intensive care unit (ICU), in developing neurosurgery as a distinct surgical specialty. Over this short 26-year history, we have gone through the difficult time of one-man-band neurosurgery, excelled in emergency neurosurgery, and evolved to an era of organized neurosurgical practice, where clinical services, teaching of undergraduate and postgraduate students, and clinical and translational research have been brought up to international standards.
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Affiliation(s)
- Wai S Poon
- Division of Neurosurgery, Department of Surgery, Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, Hong Kong.
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Wilson JRF, Green A. Acute Traumatic Brain Injury: A Review of Recent Advances in Imaging and Management. Eur J Trauma Emerg Surg 2009; 35:176. [PMID: 26814773 DOI: 10.1007/s00068-008-8095-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2008] [Accepted: 12/06/2008] [Indexed: 10/21/2022]
Abstract
Acute traumatic brain injury (TBI) is a major cause of death and disability in young persons worldwide, producing a substantial economic burden on health services. New technology in computed tomography and magnetic resonance imaging is allowing the acquisition of more accurate and detailed information on cerebral pathology post-TBI. This has greatly improved prognostic ability in TBI and enables earlier identification of pathology, making it potentially amenable to therapeutic intervention. Recent advances in the management of TBI have been hampered by a lack of class I evidence arising from difficulties in applying strict study protocols to a patient subset as heterogeneous as post-TBI patients. The most definite benefits in terms of survival after TBI come from admission to a specialist neurosurgical centre, with goal-targeted therapy and intensive care services. Some traditional therapies for the treatment of acute TBI have been proven to be harmful and should be avoided. A number of management strategies have proved potentially beneficial post-TBI, but there is insufficient evidence to make definitive recommendations at present. Future therapies that are currently under investigation include decompressive craniectomy, progesterone therapy, and possibly therapeutic hypothermia.
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Affiliation(s)
- Jamie R F Wilson
- University of Oxford Medical Sciences Division, John Radcliffe Hospital, Headley Way, Headington, Oxford, UK. .,University of Oxford Medical Sciences Division, John Radcliffe Hospital, Headley Way, Headington, Oxford, OX39DU, UK.
| | - Alex Green
- Department of Neurosurgery, West Wing, John Radcliffe Hospital, Oxford, UK
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Abstract
PURPOSE OF REVIEW Developments in imaging following traumatic brain injury are outlined. Numerous techniques have evolved over the past several years giving us more information about the injury and prognosis for recovery. Some of these techniques are in clinical use while others are used primarily in research but have the potential to become clinically useful. RECENT FINDINGS Computed tomography (CT) scanning is the primary imaging technique for acute brain injury, giving rapid information and being part of a general trauma work up in the emergency situation. It has supplanted plain films in the immediate management of brain injury. Following stabilization, MRI is the method of choice for evaluating the full extent of brain injury. Information on diffuse axonal injury is obtained by several MRI sequences. Diffusion tensor imaging is able to show long tract damage and relates to prognosis. There are several techniques which are best suited to research in brain injury, including single photon emission CT, PET and xenon CT. SUMMARY CT and MRI are now the imaging techniques for acute and subacute brain injury, respectively. Diffusion tensor imaging is being developed to provide more information on structural damage in brain injury. There are several research techniques available for brain injury, particularly relating to cerebral blood flow and metabolism.
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Abstract
Head injury remains an important cause of death and disability in young adults. This review will discuss the role of structural imaging using computed tomography (CT) and magnetic resonance imaging (MRI) and physiological imaging using CT perfusion, 131Xe CT, MRI and spectroscopy (MRS), single photon emission computed tomography, and positron emission tomography (PET) in the assessment, management, and prediction of outcome after head injury. CT allows rapid assessment of brain pathology which ensures patients who require urgent surgical intervention receive appropriate care. Although MRI provides greater spatial resolution, particularly within the posterior fossa and deep white matter, a complete assessment of the burden of injury requires imaging of cerebral physiology. Physiological imaging techniques can only provide 'snap shots' of physiology within the injured brain, but they can be repeated, and such data can be used to assess the impact of therapeutic interventions. Perfusion imaging based on CT techniques (xenon CT and CT perfusion) can be implemented easily in most hospital centres, and provide quantitative perfusion data in addition to structural images. PET imaging provides unparalleled insights into cerebral physiology and pathophysiology, but is not widely available and is primarily a research tool. MR technology continues to develop and is becoming generally available. Using a complex variety of sequences, MR can provide data concerning both structural and physiological derangements. Future developments with such imaging techniques should improve understanding of the pathophysiology of brain injury and provide data that should improve management and prediction of functional outcome.
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Affiliation(s)
- J P Coles
- University Department of Anaesthesia, Addenbrooke's Hospital, Box 93, Hills Road, Cambridge CB2 2QQ, UK.
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Abstract
Transcranial Doppler has several practical applications in neurocritical care. It has its main application in the diagnosis and monitoring of vasospasm in patients with subarachnoid hemorrhage. In addition, it holds promise for the detection of critical elevations of intracranial pressure. Its ability to measure CO2 reactivity and autoregulation may ultimately allow intensivists to optimize cerebral perfusion pressure and ventilatory therapy for the individual patient. Transcranial Doppler findings of brain death are well described and can be useful as a screening tool.
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Affiliation(s)
- Maher Saqqur
- Department of Critical Care Medicine, University of Calgary, Calgary, Alberta, Canada
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