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Zhang Z, Hwang M, Kilbaugh TJ, Sridharan A, Katz J. Cerebral microcirculation mapped by echo particle tracking velocimetry quantifies the intracranial pressure and detects ischemia. Nat Commun 2022; 13:666. [PMID: 35115552 PMCID: PMC8814032 DOI: 10.1038/s41467-022-28298-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Accepted: 01/14/2022] [Indexed: 12/26/2022] Open
Abstract
Affecting 1.1‰ of infants, hydrocephalus involves abnormal accumulation of cerebrospinal fluid, resulting in elevated intracranial pressure (ICP). It is the leading cause for brain surgery in newborns, often causing long-term neurologic disabilities or even death. Since conventional invasive ICP monitoring is risky, early neurosurgical interventions could benefit from noninvasive techniques. Here we use clinical contrast-enhanced ultrasound (CEUS) imaging and intravascular microbubble tracking algorithms to map the cerebral blood flow in hydrocephalic pediatric porcine models. Regional microvascular perfusions are quantified by the cerebral microcirculation (CMC) parameter, which accounts for the concentration of micro-vessels and flow velocity in them. Combining CMC with hemodynamic parameters yields functional relationships between cortical micro-perfusion and ICP, with correlation coefficients exceeding 0.85. For cerebral ischemia cases, the nondimensionalized cortical micro-perfusion decreases by an order of magnitude when ICP exceeds 50% of the MAP. These findings suggest that CEUS-based CMC measurement is a plausible noninvasive method for assessing the ICP and detecting ischemia.
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Affiliation(s)
- Zeng Zhang
- Department of Mechanical Engineering, Johns Hopkins University, Baltimore, MD, USA
| | - Misun Hwang
- Department of Radiology, Children's Hospital of Philadelphia, Philadelphia, PA, USA.,Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Todd J Kilbaugh
- Department of Anesthesiology and Critical Care Medicine, Children's Hospital of Philadelphia, Philadelphia, PA, USA
| | - Anush Sridharan
- Department of Radiology, Children's Hospital of Philadelphia, Philadelphia, PA, USA
| | - Joseph Katz
- Department of Mechanical Engineering, Johns Hopkins University, Baltimore, MD, USA.
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Invasive and ultrasound based monitoring of the intracranial pressure in an experimental model of epidural hematoma progressing towards brain tamponade on rabbits. ScientificWorldJournal 2014; 2014:504248. [PMID: 24578637 PMCID: PMC3918727 DOI: 10.1155/2014/504248] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Accepted: 11/12/2013] [Indexed: 11/17/2022] Open
Abstract
INTRODUCTION An experimental epidural hematoma model was used to study the relation of ultrasound indices, namely, transcranial color-coded-Doppler (TCCD) derived pulsatility index (PI), optic nerve sheath diameter (ONSD), and pupil constriction velocity (V) which was derived from a consensual sonographic pupillary light reflex (PLR) test with invasive intracranial pressure (ICP) measurements. MATERIAL AND METHODS Twenty rabbits participated in the study. An intraparenchymal ICP catheter and a 5F Swan-Ganz catheter (SG) for the hematoma reproduction were used. We successively introduced 0.1 mL increments of autologous blood into the SG until the Cushing reaction occurred. Synchronous ICP and ultrasound measurements were performed accordingly. RESULTS A constant increase of PI and ONSD and a decrease of V values were observed with increased ICP values. The relationship between the ultrasound variables and ICP was exponential; thus curved prediction equations of ICP were used. PI, ONSD, and V were significantly correlated with ICP (r² = 0.84 ± 0.076, r² = 0.62 ± 0.119, and r² = 0.78 ± 0.09, resp. (all P < 0.001)). CONCLUSION Although statistically significant prediction models of ICP were derived from ultrasound indices, the exponential relationship between the parameters underpins that results should be interpreted with caution and in the current experimental context.
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Naranjo D, Arkuszewski M, Rudzinski W, Melhem ER, Krejza J. Brain ischemia in patients with intracranial hemorrhage: pathophysiological reasoning for aggressive diagnostic management. Neuroradiol J 2013; 26:610-28. [PMID: 24355179 PMCID: PMC4202872 DOI: 10.1177/197140091302600603] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Accepted: 10/15/2013] [Indexed: 11/15/2022] Open
Abstract
Patients with intracranial hemorrhage have to be managed aggressively to avoid or minimize secondary brain damage due to ischemia, which contributes to high morbidity and mortality. The risk of brain ischemia, however, is not the same in every patient. The risk of complications associated with an aggressive prophylactic therapy in patients with a low risk of brain ischemia can outweigh the benefits of therapy. Accurate and timely identification of patients at highest risk is a diagnostic challenge. Despite the availability of many diagnostic tools, stroke is common in this population, mostly because the pathogenesis of stroke is frequently multifactorial whereas diagnosticians tend to focus on one or two risk factors. The pathophysiological mechanisms of brain ischemia in patients with intracranial hemorrhage are not yet fully elucidated and there are several important areas of ongoing research. Therefore, this review describes physiological and pathophysiological aspects associated with the development of brain ischemia such as the mechanism of oxygen and carbon dioxide effects on the cerebrovascular system, neurovascular coupling and respiratory and cardiovascular factors influencing cerebral hemodynamics. Consequently, we review investigations of cerebral blood flow disturbances relevant to various hemodynamic states associated with high intracranial pressure, cerebral embolism, and cerebral vasospasm along with current treatment options.
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Affiliation(s)
- Daniel Naranjo
- Department of Diagnostic Radiology of the University of Maryland, Division of Clinical Research; Baltimore, Maryland, USA
| | - Michal Arkuszewski
- Department of Neurology, Medical University of Silesia, Central University Hospital; Katowice, Poland
| | - Wojciech Rudzinski
- Department of Cardiology, Robert Packer Hospital; Sayre, Pennsylvania USA
| | - Elias R. Melhem
- Department of Diagnostic Radiology of the University of Maryland, Division of Clinical Research; Baltimore, Maryland, USA
| | - Jaroslaw Krejza
- Department of Diagnostic Radiology of the University of Maryland, Division of Clinical Research; Baltimore, Maryland, USA
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Wagshul ME, Eide PK, Madsen JR. The pulsating brain: A review of experimental and clinical studies of intracranial pulsatility. Fluids Barriers CNS 2011; 8:5. [PMID: 21349153 PMCID: PMC3042979 DOI: 10.1186/2045-8118-8-5] [Citation(s) in RCA: 251] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2010] [Accepted: 01/18/2011] [Indexed: 02/01/2023] Open
Abstract
The maintenance of adequate blood flow to the brain is critical for normal brain function; cerebral blood flow, its regulation and the effect of alteration in this flow with disease have been studied extensively and are very well understood. This flow is not steady, however; the systolic increase in blood pressure over the cardiac cycle causes regular variations in blood flow into and throughout the brain that are synchronous with the heart beat. Because the brain is contained within the fixed skull, these pulsations in flow and pressure are in turn transferred into brain tissue and all of the fluids contained therein including cerebrospinal fluid. While intracranial pulsatility has not been a primary focus of the clinical community, considerable data have accrued over the last sixty years and new applications are emerging to this day. Investigators have found it a useful marker in certain diseases, particularly in hydrocephalus and traumatic brain injury where large changes in intracranial pressure and in the biomechanical properties of the brain can lead to significant changes in pressure and flow pulsatility. In this work, we review the history of intracranial pulsatility beginning with its discovery and early characterization, consider the specific technologies such as transcranial Doppler and phase contrast MRI used to assess various aspects of brain pulsations, and examine the experimental and clinical studies which have used pulsatility to better understand brain function in health and with disease.
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Affiliation(s)
- Mark E Wagshul
- Albert Einstein College of Medicine, Department of Radiology, Bronx, NY 10461, USA.
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Mapping vascular response to in vivo Hemodynamics: application to increased flow at the basilar terminus. Biomech Model Mechanobiol 2010; 9:421-34. [DOI: 10.1007/s10237-009-0185-y] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2009] [Accepted: 12/21/2009] [Indexed: 10/20/2022]
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Splavski B, Radanović B, Muzević D, Has B, Janculjak D, Kristek J, Jukić D. Assessment of intra-cranial pressure after severe traumatic brain injury by transcranial Doppler ultrasonography. Brain Inj 2007; 20:1265-70. [PMID: 17132549 DOI: 10.1080/02699050601082099] [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
PRIMARY OBJECTIVE To investigate the potential of transcranial Doppler ultrasonography in estimating post-traumatic intra-cranial pressure early after severe traumatic brain injury. RESEARCH DESIGN The group of 24 patients was analysed for the observation of an early post-traumatic cerebral haemodynamic by middle cerebral artery blood velocity measuring. METHODS AND PROCEDURES The standard method of measuring the mean blood middle cerebral artery velocity by transcranial Doppler ultrasonic device was performed. MAIN OUTCOMES AND RESULTS The increased duration of intra-cranial hypertension correlated to the middle cerebral artery low blood velocity (p = 0.042; r = -0.498) (n = 17) and to elevated pulsatility indices (p = 0.007; r = 0.753) (n = 11) significantly. The increased duration of lowered cerebral perfusion pressure correlated to the middle cerebral artery low blood velocity significantly (p = 0.001; r = -0.619) (n = 24). CONCLUSIONS The significance of transcranial Doppler ultrasonography as a method to estimate an early post-traumatic intra-cranial pressure after severe brain injury was confirmed. This simple and non-invasive technique could be easily used in daily clinical practice and precede intra-cranial pressure monitoring in selected patients.
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Affiliation(s)
- Bruno Splavski
- Division of Neurosurgery, Clinical Hospital, Osijek, Croatia.
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Lee CH, Chang HY, Chen CW, Hsiue TR. The role of nitric oxide in the spatial heterogeneity of basal microvascular blood flow in the rat diaphragm. J Biomed Sci 2005; 12:197-207. [PMID: 15864750 DOI: 10.1007/s11373-004-8166-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2004] [Accepted: 11/04/2004] [Indexed: 11/26/2022] Open
Abstract
The effects of N omega-nitro-L: -arginine (L: -NOARG) and N(G)-monomethyl-L: -arginine (L: -NMMA) on the spatial distribution of diaphragmatic microvascular blood flow were assessed in anesthetized, mechanically ventilated rats. Microvascular blood flow was measured after different periods at either a fixed site (Q stat) or 25 different sites (Q scan) using computer-aided laser-Doppler flowmetry (LDF) scanning. The value of Q stat was unaffected after 15-20 min superfusion with any one of the following agents: L: -NOARG (0.1 mM), L: -NMMA (0.1 mM), L: -arg (10 mM). The cumulative frequency histogram of the Q scan value in the control group displayed a non-Gaussian distribution that was not significantly affected after 15 min superfusion with the vehicle of L: -NOARG. Superfusion with either L: -NMMA or L: -NOARG at 0.1 mM for 15 min displaced the histogram of cumulative frequency to the left, with the median value of blood flow decreasing by 10 to 20%. However, skewness and kurtosis of the distribution of basal Q(scan) were unaffected after superfusion of either of the L: -arg analogues. Pretreatment with L: -arg (10 mM), followed by co-administration of L: -arg (10 mM) with L: -NOARG (0.1 mM) only partially prevented L: -NOARG from exerting this inhibitory effect on the distribution of basal Q scan, while pretreatment with L: -arg in the same manner could prevent L: -NMMA from exerting its inhibitory effect. There was a weak but significant linear relationship between the magnitude of basal Q(scan) and normalized changes in basal Q scan after superfusion of either of the L: -arg analogues. In conclusion, a basal NO activity is present in the diaphragmatic microvascular bed of rats. LDF scanning rather may yield more vivid information about the extent of overall tissue perfusion than conventional LDF whenever basal NO activity is involved. Moreover, the parallel flow profiles after NO synthase blockade suggest that the spatial inhomogeneity of basal diaphragmatic microvascular blood flow is not dependent on basal NO formation.
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Affiliation(s)
- Cheng-Hung Lee
- Department of Internal Medicine, College of Medicine, National Cheng Kung University, 704 Tainan, Taiwan. ROC
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Cağavi F, Kalayci M, Ozer Y, Oz OO, Açikgöz B. Dispersion of cerebral temperature, cerebral perfusion and intracranial pressure in rabbits placed with epidural balloons. Brain Res Bull 2005; 64:481-5. [PMID: 15639543 DOI: 10.1016/j.brainresbull.2004.10.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2004] [Revised: 09/27/2004] [Accepted: 10/10/2004] [Indexed: 11/25/2022]
Abstract
This study examines the intracranial pressure and temperature dispersion in a rabbit model after epidural balloon compression. Right and left supratentorial, intraventricular and infratentorial pressures and temperatures of the rabbits have been measured before epidural balloon was placed. Afterwards, the epidural balloon was placed in right parietal epidural area. The intracranial pressure and temperature dispersion values were recorded after inflation with 0.3 and 0.6 ml, respectively. The control values of intracranial pressure measurements of four different brain regions were found to be similar. When the balloon was inflated to 0.3 ml, the intracranial pressure distribution was found to be equal in all the fields. After the balloon was inflated up to 0.6 ml, right and left supratentorial intracranial pressure values were found to be equal. However, infratentorial pressure values were lower and intraventricular pressure values were higher when compared with the right hemisphere. Before the inflation and at two different inflation volumes, perfusion pressure and temperature dispersion were found to be similar between right hemisphere and other compartments. We conclude that, the effective mechanism in cerebral temperature regulation may be related to preserved cerebral perfusion pressure and cerebral blood flow.
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Affiliation(s)
- Ferda Cağavi
- Zonguldak Karaelmas University, Department of Neurosurgery, Zonguldak 67600, Turkey.
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Soehle M, Czosnyka M, Pickard JD, Kirkpatrick PJ. Continuous assessment of cerebral autoregulation in subarachnoid hemorrhage. Anesth Analg 2004; 98:1133-1139. [PMID: 15041613 DOI: 10.1213/01.ane.0000111101.41190.99] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
UNLABELLED Cerebral vasospasm remains a leading cause of morbidity and mortality after subarachnoid hemorrhage (SAH). Cerebral ischemia may ensue when autoregulation fails to compensate for spasm. We examined how autoregulation is affected by vasospasm by using transcranial Doppler. The moving correlation coefficient between slow changes of arterial blood pressure and mean or systolic flow velocity (FV), termed "Mx" and "Sx," respectively, was used to characterize cerebral autoregulation. Vasospasm was declared when the mean FV increased to more than 120 cm/s and the Lindegaard ratio was more than 3. This occurred in 15 of 32 SAH patients. On the basis of the bilateral transcranial Doppler recordings of the middle cerebral artery in vasospastic patients, Mx and Sx were calculated for baseline and vasospasm. Mx increased during vasospasm (0.46 +/- 0.32; mean +/- SD) and was significantly higher (P = 0.021) than at baseline (0.21 +/- 0.24). Sx was also increased (0.22 +/- 0.26 vs 0.05 +/- 0.21 at baseline; P = 0.03). Mx correlated with mean FV (r = 0.577; P = 0.025) and the Lindegaard ratio (r = 0.672; P < 0.006). Mx (P = 0.006) and Sx (P = 0.044) were higher on the vasospastic side (Mx, 0.44 +/- 0.27; Sx, 0.24 +/- 0.23) when compared with the contralateral side (Mx, 0.34 +/- 0.29; Sx, 0.16 +/- 0.25). The increased Mx and Sx during cerebral vasospasm demonstrate impaired cerebral autoregulation. Mx and Sx provide additional information on changes in autoregulation in SAH patients. IMPLICATIONS The moving correlation coefficients between slow changes of arterial blood pressure and mean or systolic flow velocity, termed "Mx" and "Sx," respectively, characterize cerebral autoregulation but have not been applied to subarachnoid hemorrhage. A study in 15 patients revealed that Mx and Sx were significantly increased, indicating impaired autoregulation during vasospasm as compared with baseline, as well as on the side of vasospasm in comparison with the contralateral side.
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Affiliation(s)
- Martin Soehle
- *Department of Anaesthesiology and Intensive Care Medicine, University of Bonn, Bonn, Germany; and †Academic Neurosurgery Unit, Addenbrooke's Hospital, University of Cambridge, Cambridge, United Kingdom
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Barbiro-Michaely E, Mayevsky A. Effects of elevated ICP on brain function: can the multiparametric monitoring system detect the 'Cushing Response'? Neurol Res 2003; 25:42-52. [PMID: 12564125 DOI: 10.1179/016164103101201102] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
The 'Cushing Response' is a significant phenomenon associated with elevated ICP. The purpose of our study was to examine the effects of the intracranial hypertension level and duration on the cerebral tissue physiology, using a Multiprobe assembly (MPA). The parameters monitored simultaneously included ICP, CBF, mitochondrial NADH redox state, extracellular K+ and H+ levels, DC potential and ECoG, calculated CPP and blood pressure. Two groups of rats were used. In one group, ICP was elevated to 50-60 mmHg for 13-15 min and, in the second group, ICP was elevated to 20 mmHg for 30 min. The results show that ICP of 50-60 mmHg led to CPP reduction below the lower limits of autoregulation. However, ICP of 20 mmHg, even for a prolonged period of time is completely tolerated. Additionally, we found that the 'Cushing Response', developed in the moderate treatment (ICP = 20 mmHg) is beneficial, assuring high CBF levels under intracranial hypertension. Furthermore, CBF and CPP monitoring, apparently, are not sufficient for autoregulation assessment; more parameters are needed.
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Burger R, Vince GH, Meixensberger J, Bendszus M, Roosen K. Interrelations of laser doppler flowmetry and brain tissue oxygen pressure during ischemia and reperfusion induced by an experimental mass lesion. J Neurotrauma 1999; 16:1149-64. [PMID: 10619194 DOI: 10.1089/neu.1999.16.1149] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The objective of this study was to assess interrelations between bilateral changes of cortical laser doppler flowmetry and intraparenchymal, subcortical partial tissue oxygen tension in the course of an experimental trauma. Ten animals served as a sham group, 8 Sprague-Dawley rats received an unilateral, focal parietal mass lesion. The bilateral course of cortical blood flow measured by laser doppler flowmetry (LDF) was correlated with subcortical, intraparenchymal partial tissue oxygen tension [p(ti)O2]. In the sham-operated group, laser doppler mean flow values drifted between 9.0% and 9.5% and showed no significant changes over time neither between the hemispheres nor within each hemisphere. Absolute mean p(ti)O2 in sham-operated animals was 32.4 mm Hg in the left and 30.5 mm Hg in the right hemisphere. In the trauma group, mean laser doppler flow values during maximum brain compression decreased ipsilateral to 20.3% and contralateral to 34.4% of the baseline values. P(ti)O2 decreased ipsilateral from 25.9 to 6.6 mm Hg (25.4%) and contralateral from 22.6 to 9.8 mm Hg (43.6%). After balloon deflation, cortical LDF was restored much faster compared to p(ti)O2, but did not reach baseline values [ipsilateral 61.6% (p < 0.05); contralateral 75.8% of baseline values]. The p(ti)O2 values reached 25.2 mm Hg (97%) ipsilateral and 23.7 mm Hg (105%) contralateral. A temporary phase of reactive hyperemia occurred sporadically shortly after decompression. Both parameters showed a significant but rather weak correlation (r = 0.56; p < 0.001). Based upon these findings, we conclude that intraparenchymal, subcortical p(ti)O2 measurements supplemented on-line cortical CBF monitoring and score out discontinuous alternative measurement techniques in detecting hemodynamically relevant events. The small spatial resolution of LDF and p(ti)O2 probes, however, which in the small animal model may be of negligible influence, does raise the question whether the values obtained represent the microcirculatory situation of the human brain.
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Affiliation(s)
- R Burger
- Department of Neurological Surgery, University of Würzberg, Germany.
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Piechnik SK, Yang X, Czosnyka M, Smielewski P, Fletcher SH, Jones AL, Pickard JD. The continuous assessment of cerebrovascular reactivity: a validation of the method in healthy volunteers. Anesth Analg 1999; 89:944-9. [PMID: 10512269 DOI: 10.1097/00000539-199910000-00023] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
UNLABELLED Using transcranial Doppler ultrasonography, we investigated the moving correlation between slow waves in arterial blood pressure (ABP) and blood flow velocity (FV) at different levels of cerebrovascular vasodilation provoked by changing PETCO2. Fourteen healthy volunteers were examined. The FV in middle cerebral arteries, PETCO2, and ABP were recorded during normocapnia, hypercapnia, and hypocapnia. The moving correlation coefficients between ABP and mean FV (FVm) or systolic FV (FVs) during spontaneous fluctuations in ABP were calculated for 3-min epochs and averaged for each investigation, thus yielding the mean index (Mx) and systolic index (Sx). As a reference method, Aaslid's cuff tests were performed to obtain the rate of regulation (RoR). RoR, Mx, and Sx significantly depended on PETCO2 (analysis of variance, P < 0.00001). At high PETCO2, cerebrovascular reactivity was disturbed as reflected in RoR values of < 0.17/s for all volunteers and increased values of Mx (> 0.4 in 86% of volunteers) and Sx (> 0.2 in 79% of volunteers). Overall, there was a reasonably good correlation of both Mx and Sx with RoR (R2 = 0.65 and 0.58, respectively). IMPLICATIONS Indices derived from the correlation between spontaneous fluctuations of blood flow velocity wave form and arterial blood pressure may be used for the noninvasive continuous monitoring of cerebrovascular reactivity.
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Affiliation(s)
- S K Piechnik
- Wolfson Brain Imaging Centre, Cambridge Medical Research Council's Centre for Brain Repair and Academic Neurosurgery Unit, Addenbrooke's Hospital, United Kingdom.
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Piechnik SK, Yang X, Czosnyka M, Smielewski P, Fletcher SH, Jones AL, Pickard JD. The Continuous Assessment of Cerebrovascular Reactivity: A Validation of the Method in Healthy Volunteers. Anesth Analg 1999. [DOI: 10.1213/00000539-199910000-00023] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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14
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Kirkeby OJ, Rise IR. Intracerebral laser Doppler blood flow measurements compared to blood flow in porcine internal carotid artery. J Clin Neurosci 1999. [DOI: 10.1016/s0967-5868(99)90033-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Ursino M, Giulioni M, Lodi CA. Relationships among cerebral perfusion pressure, autoregulation, and transcranial Doppler waveform: a modeling study. J Neurosurg 1998; 89:255-66. [PMID: 9688121 DOI: 10.3171/jns.1998.89.2.0255] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
OBJECT The aim of this study was to analyze how the main values extrapolated from the transcranial Doppler (TCD) waveform (systolic, mean, and diastolic velocity; velocity peak-to-peak amplitude; and pulsatility index [PI]) are affected by changes in intracranial pressure (ICP), systemic arterial pressure (SAP), autoregulation, and intracranial compliance. METHODS The analysis was performed using a mathematical model of the intracranial dynamics. This model includes a passive middle cerebral artery, the biomechanics of large and small pial arteries subjected to autoregulatory mechanisms, a collapsing venous cerebrovascular bed, the cerebrospinal fluid circulation, and the ICP-volume relationship. The results indicate that there are approximately three distinct zones characterized by different relationships between cerebral perfusion pressure (CPP) and velocity parameters in patients with preserved autoregulation. In the central autoregulatory zone (CPP > 70 mm Hg) the mean velocity does not change with decreasing CPP, whereas the PI and velocity peak-to-peak amplitude increase moderately. In a second zone (CPP between 4045 and 70 mm Hg), in which vasodilation of small pial arteries becomes maximal, the mean velocity starts to decrease, whereas the PI and velocity amplitude continue to increase. In the third zone, in which autoregulation is completely exhausted (CPP < 40 mm Hg), arterioles behave passively, mean velocity and velocity amplitude decline abruptly, and the PI exhibits a disproportionate rise. Moreover, this rise is quite independent of whether CPP is reduced by increasing ICP or reducing mean SAP. In contrast, in patients with defective autoregulation, the mean velocity and velocity amplitude decrease linearly with decreasing CPP, but the PI still increases in a way similar to that observed in patients with preserved autoregulation. CONCLUSIONS The information contained in the TCD waveform is affected by many factors, including ICP, SAP, autoregulation. and intracranial compliance. Model results indicate that only a comparative analysis of the concomitant changes in ultrasonographic quantities during multimodality monitoring may permit the assessment of several aspects of intracranial dynamics (cerebral blood flow changes, vascular pulsatility, ICP changes, intracranial compliance, CPP, and autoregulation).
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Affiliation(s)
- M Ursino
- Department of Electronics, Computer Science and Systems, University of Bologna, Italy
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16
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Czosnyka M, Piechnik S, Richards HK, Kirkpatrick P, Smielewski P, Pickard JD. Contribution of mathematical modelling to the interpretation of bedside tests of cerebrovascular autoregulation. J Neurol Neurosurg Psychiatry 1997; 63:721-31. [PMID: 9416805 PMCID: PMC2169860 DOI: 10.1136/jnnp.63.6.721] [Citation(s) in RCA: 105] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
OBJECTIVES Cerebral haemodynamic responses to short and longlasting episodes of decreased cerebral perfusion pressure contain information about the state of autoregulation of cerebral blood flow. Mathematical simulation may help to elucidate which of the indices, that can be derived using transcranial Doppler ultrasonography and trends of intracranial pressure and blood pressure, are useful in clinical tests of autoregulatory reserve. METHODS Time dependent interactions between pressure, flow, and volume of cerebral blood and CSF were modelled using a set of non-linear differential equations. The model simulates changes in arterial blood inflow and storage, arteriolar and capillary blood flow controlled by cerebral autoregulation, venous blood storage and venous outflow modulated by changes in ICP, and CSF storage and reabsorption. The model was used to simulate patterns of blood flow during either short or longlasting decreases in cerebral perfusion pressure. These simulations can be considered as clinically equivalent to a short compression of the common carotid artery, systemic hypotension, and intracranial hypertension. Simulations were performed in autoregulating and non-autoregulating systems and compared with recordings obtained in patients. RESULTS After brief compression of the common carotid artery, a subsequent transient hyperaemia can be interpreted as evidence of intact autoregulation. During longlasting sustained hypoperfusion, a gradual increase in the systolic value of the blood flow velocity waveform along with a decrease in the diastolic value is specific for an autoregulating cerebrovascular system. CONCLUSION Modelling studies help to interpret both clinical and experimental cerebral haemodynamic phenomena and their dependence on the state of autoregulation.
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Affiliation(s)
- M Czosnyka
- Wolfson Brain Imaging Centre, Addenbrooke's Hospital, Cambridge, UK.
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Beiner JM, Olgivy CS, DuBois AB. Cerebral blood flow changes in response to elevated intracranial pressure in rabbits and bluefish: a comparative study. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. PART A, PHYSIOLOGY 1997; 116:245-52. [PMID: 9102186 DOI: 10.1016/s0300-9629(96)00206-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
In mammals, the cerebrovascular response to increases in intracranial pressure may take the form of the Cushing response, which includes increased mean systemic arterial pressure, bradycardia and diminished respirations. The mechanism, effect and value of these responses are debated. Using laser-Doppler flowmetry to measure cerebral blood flow, we analyzed the cardiovascular responses to intracranial pressure raised by epidural infusion of mock cerebrospinal fluid in the bluefish and in the rabbit, and compare the results. A decline in cerebral blood flow preceding a rise in mean systemic arterial pressure was observed in both species. Unlike bluefish, rabbits exhibit a threshold of intracranial pressure below which cerebral blood flow was maintained and no cardiovascular changes were observed. The difference in response between the two species was due to the presence of an active autoregulatory system in the cerebral tissue of rabbits and its absence in bluefish. For both species studied, the stimulus for the Cushing response seems to be a decrement in cerebral blood flow. The resulting increase in the mean systemic arterial pressure restores cerebral blood flow to levels approaching controls.
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Affiliation(s)
- J M Beiner
- Yale University School of Medicine, New Haven, CT 06510, USA.
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Nagai H, Moritake K, Takaya M. Correlation between transcranial Doppler ultrasonography and regional cerebral blood flow in experimental intracranial hypertension. Stroke 1997; 28:603-7; discussion 608. [PMID: 9056619 DOI: 10.1161/01.str.28.3.603] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
BACKGROUND AND PURPOSE Transcranial Doppler ultrasonography (TCD) provides useful information on cerebral circulation even under raised intracranial pressure. This study was designed to evaluate the correlation between cerebral blood flow (CBF) and TCD parameters under conditions of boundary intracranial hypertension that can cause brain death. METHODS Intracranial pressure was raised by inflation of a supratentorial epidural balloon in cats. Blood flow velocity of the middle cerebral artery was measured transorbitally with microvascular Doppler sonography, and intracranial pressure and CBF were evaluated. RESULTS In this study, four characteristic flow patterns were observed, appearing in the following order with progressive increases in intracranial pressure: sharp wave, systolic flow, systolic spike, and no flow. These flow patterns showed a significant correlation with flow velocity, CBF, the pulsatility index, and cerebral perfusion pressure. The systolic-spike and no-flow patterns and pulsatility index over 4.0 indicated decreased CBF, under 10% of control values. CONCLUSIONS The critical level of brain circulation can be detected by Doppler sonography, indicating that TCD is available as a tool for the assessment of cerebral circulatory arrest in brain death.
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Affiliation(s)
- H Nagai
- Department of Neurosurgery, Shimane Medical University, Japan.
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Richards HK, Kozniewska E, Czosnyka M, Pickard JD. Changes in transcranial Doppler flow velocity waveform following inhibition of nitric oxide synthesis. Experimental study in anaesthetised rabbits. Acta Neurochir (Wien) 1997; 139:63-9; discussion 69-70. [PMID: 9059714 DOI: 10.1007/bf01850870] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
BACKGROUND Analysis of the transcranial Doppler blood flow velocity (FV) waveform is used clinically to detect changes in cerebral haemodynamic profile. Such changes may be initiated both by alterations in microvascular resistance and in the tone of the cerebral arteries. METHODS The role of endothelial mechanisms was investigated using inhibition of NO synthesis by systemic administration of NG-nitro-L-arginine methyl ester (L-NAME, 6 mg/kg) followed by simultaneous monitoring of both basilar artery FV and cerebrocortical microcirculation (laser Doppler flowmetry, LDF) in anaesthetised, ventilated rabbits over 60 minutes. RESULTS Arterial blood pressure (AP) increased significantly (p < 0.01) above baseline level in the second minute following L-NAME and remained elevated until the end of experiment. Time average mean and systolic FV decreased immediately following L-NAME injection, with the statistically significant (p < 0.01) decrease from the third minute. Diastolic FV did not show such radical changes. LDF exhibited a slow decrease with time becoming significantly lower than baseline (p < 0.01) at 50 min. CONCLUSION A gradual decrease in cortical microcirculation preceded by a rapid reaction recorded in the TCD waveform implies that an increase in the tone of the great cerebral arteries is the predominant phenomenon seen during the acute phase of NO synthase inhibition.
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Affiliation(s)
- H K Richards
- MRC Cambridge Centre for Brain Repair, Addenbrooke's Hospital, UK
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Mayer SA, Thomas CE, Diamond BE. Asymmetry of intracranial hemodynamics as an indicator of mass effect in acute intracerebral hemorrhage. A transcranial Doppler study. Stroke 1996; 27:1788-92. [PMID: 8841331 DOI: 10.1161/01.str.27.10.1788] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
BACKGROUND AND PURPOSE Hematoma volume is an important determinant of outcome and predictor of clinical deterioration in patients with intracerebral hemorrhage. In many cases, worsening results from herniation due to compartmentalized pressure gradients. We used transcranial Doppler sonography (TCD) to assess the impact of hematoma volume on symmetry of intracranial hemodynamics in patients with acute intracerebral hemorrhage. The goal was to evaluate TCD as a noninvasive method for monitoring compartmentalized mass effect. METHODS TCD was performed an average of 1.1 days (range, 0 to 3 days) after onset in 30 patients with supratentorial intracerebral hemorrhage. Hematoma, hematoma + edema, and intraventricular hemorrhage volumes were calculated from admission CT scans using computerized planimetry and were compared with combined TCD values from the middle cerebral and internal carotid arteries. RESULTS Ipsilateral pulsatility indexes were consistently elevated and mean velocities consistently depressed when intracerebral hemorrhage volumes exceeded 25 mL. Compared with patients with small hemorrhages, those with large hemorrhages (> or = 25 mL, n = 10) had significantly higher ipsilateral pulsatility indexes (1.72 versus 1.13, P < .0001) and higher ratios of ipsilateral-to-contralateral pulsatility (1.29 versus 1.06, P = .001). The ratio of ipsilateral-to-contralateral mean velocity was similarly reduced in patients with large versus small hemorrhages (0.87 versus 1.06, P = .01), but this effect was less pronounced. In a multiple regression analysis, ipsilateral and contralateral pulsatility indexes correlated primarily with intraventricular hemorrhage volume (P < .001), whereas the ratio of ipsilateral-to-contralateral pulsatility correlated with total hemispheric lesion (hematoma + edema) volume (P = .003). CONCLUSIONS Asymmetry of intracranial hemodynamics as assessed by TCD occurs when intracerebral hemorrhage volumes exceed 25 mL. Alterations of pulsatility index reflect intracranial lesion volume more reliably than mean velocity. Although pulsatility is strongly influenced by the presence of intraventricular blood, elevated ratios of ipsilateral-to-contralateral pulsatility correlate primarily with hemispheric lesion volume and may reflect compartmentalized intracranial pressure gradients.
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Affiliation(s)
- S A Mayer
- Department of Neurology, Columbia-Presbyterian Medical Center, New York, NY, USA.
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Diehl RR, Linden D, Chalkiadaki A, Ringelstein EB, Berlit P. Transcranial Doppler during neurocardiogenic syncope. Clin Auton Res 1996; 6:71-4. [PMID: 8726090 DOI: 10.1007/bf02291226] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The purpose of the present study was to investigate changes in cerebral circulation during neurocardiogenic syncope (NCS). Twenty patients with a history of unexplained syncopes were studied over a 45 min period in a tilted position. Heart rate and arterial blood pressure were recorded non-invasively using Finapres. Cerebral blood flow velocity of both middle cerebral arteries was measured with transcranial Doppler (TCD). Ten patients (50%) developed a NCS during the tilt test, with a strong reduction in blood pressure (mean, 48/34 mmHg) and heart rate (mean, 54 beats/min). Simultaneously, diastolic blood flow velocities dropped to values close to zero. However, systolic blood flow velocities did not decrease. In consequence, the pulsatility index (PI) increased considerably from 0.93 to 2.01. The increase in PI suggests that there is a constriction of cerebral resistance vessels during NCS. Despite the drop in blood pressure and the putative increase in cerebrovascular resistance, systolic blood flow velocities remained unchanged in the TCD records. This fact can be explained by a lumen narrowing of the middle cerebral artery at the site of insonation. In conclusion, the typical changes in cerebral blood flow velocity during NCS are probably due to a strong constriction of both the proximal and the peripheral segments of cerebral arteries. It is clear that, in addition to vasodepression and cardiac inhibition, cerebral vasoconstriction is a further mechanism in the pathogenesis of a NCS.
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Affiliation(s)
- R R Diehl
- Department of Neurology and Clinical Neurophysiology, Alfried Krupp Hospital, Essen, Germany
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Czosnyka M, Richards HK, Whitehouse HE, Pickard JD. Relationship between transcranial Doppler-determined pulsatility index and cerebrovascular resistance: an experimental study. J Neurosurg 1996; 84:79-84. [PMID: 8613840 DOI: 10.3171/jns.1996.84.1.0079] [Citation(s) in RCA: 145] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Clinical studies with transcranial Doppler suggest that the pulsatility of the flow velocity (FV) waveform increases when the distal cerebrovascular resistance (CVR) increases. To clarify this relationship, the authors studied animal models in which the resistance may be decreased in a controlled manner by an increase in arterial CO2 tension, or by a decrease in cerebral perfusion pressure (CPP) in autoregulating animals. Twelve New Zealand white rabbits were anesthetized, paralyzed, and ventilated. Transcranial Doppler basilar artery FV, laser Doppler cortical blood flow, arterial pressure, intracranial pressure, and end-tidal CO2 concentration were measured continuously. Cerebrovascular resistance (CPP divided by laser Doppler cortical flux) and Gosling Pulsatility Index (PI, defined as an FV pulse amplitude divided by a timed average FV) were calculated as time-dependent variables for each animal. Four groups of animals undergoing controlled manipulations of CVR were analyzed. In Group I, arterial CO2 concentration was changed gradually from hypocapnia to hypercapnia. In Group II, gradual hemorrhagic hypotension was used to reduce CPP. In Group III, the short-acting ganglion blocking drug trimetaphan was injected intravenously to induce transient hypotension. Intracranial hypertension was produced by subarachnoid saline infusion in Group IV. During the hypercapnic challenge the correlation between the cortical resistance and Doppler flow pulsatility was positive (r = 0.77, p<0.001). In all three groups in which cerebral perfusion pressure was reduced a negative correlation between pulsatility index and cerebrovascular resistance was found (r = -0.84, p<0.001). The authors conclude that PI cannot be interpreted simply as an index of CVR in all circumstances.
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Affiliation(s)
- M Czosnyka
- MRC Cambridge Centre for Brain Repair, Addenbrooke's Hospital, Cambridge, England
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