Imbalanced flow changes of distal arteries: An important factor in process of delayed ipsilateral parenchymal hemorrhage after flow diversion in patients with cerebral aneurysms

2021 ◽  
pp. 159101992110091
Author(s):  
Wenqiang Li ◽  
Wei Zhu ◽  
Jian Liu ◽  
Xinjian Yang
Keyword(s):  
Blood Flow ◽  
Cerebral Artery ◽  
Cerebral Aneurysms ◽  
Flow Distribution ◽  
Maximum Flow ◽  
Flow Diverter ◽  
Control Group ◽  
Blood Flow Distribution ◽  
Mean Velocity ◽  
The Mean

Background and objective Hemodynamic forces may play a role in symptomatic delayed ipsilateral parenchymal hemorrhage (DIPH) of intracranial aneurysm (IA) after flow diverter placement. We aimed to investigate the hemodynamic risk factors in the postsurgical DIPH process. Methods Six patients with internal carotid artery (ICA) aneurysm developed to DIPH and 12 patients without DIPH (1:2 matched controls) after flow diverter were included between January 2015 to January 2019. Postsurgical hemodynamics of distal arteries (terminal ICA, middle cerebral artery (MCA), anterior cerebral artery (ACA)) were investigated using computational fluid dynamics, as well as the hemodynamic alteration between pre- and post-treatment. The DIPH related and unrelated distal arteries (either MCA or ACA) were discriminated and compared. Definition of imbalance index is the difference in increased velocity post-flow diverter between MCA and ACA and was used to evaluate the blood flow distribution of distal arteries. Results The mean and maximum flow velocities in the terminal ICA increased significantly after treatment in both groups. In DIPH group, the increase rate of mean velocity in the DIPH-related artery was significantly higher than that in DIPH-unrelated artery after the treatment (20.98 ± 15.38% vs −6.40 ± 7.74%; p = 0.028). Between the DIPH and control group, the baseline characteristics were well matched. However, a higher imbalance index of mean velocity was found in DIPH group (27.38 ± 13.03% vs 10.85 ± 14.12%; p = 0.031). Conclusion The mean velocity of DIPH related artery increased more, and the imbalance in increased blood flow distribution of distal arteries might play an important role in DIPH after flow diverter of IAs.

Hemodilution during Venous Gas Embolization Improves Gas Exchange, without Altering V̇A/Q̇ or Pulmonary Blood Flow Distributions 

1999 ◽  
Vol 91 (6) ◽  
pp. 1861-1861 ◽  
Author(s):  
Steven Deem ◽  
Steven McKinney ◽  
Nayak L. Polissar ◽  
Richard G. Hedges ◽  
Erik R. Swenson
Keyword(s):  
Blood Flow ◽  
Gas Exchange ◽  
Lung Injury ◽  
Partial Pressure ◽  
Pulmonary Blood Flow ◽  
Flow Distribution ◽  
Arterial Oxygen ◽  
Control Group ◽  
Blood Flow Distribution ◽  
Over Time

Background Isovolemic anemia results in improved gas exchange in rabbits with normal lungs but in relatively poorer gas exchange in rabbits with whole-lung atelectasis. In the current study, the authors characterized the effects of hemodilution on gas exchange in a distinct model of diffuse lung injury: venous gas embolization. Methods Twelve anesthetized rabbits were mechanically ventilated at a fixed rate and volume. Gas embolization was induced by continuous infusion of nitrogen via an internal jugular venous catheter. Serial hemodilution was performed in six rabbits by simultaneous withdrawal of blood and infusion of an equal volume of 6% hetastarch; six rabbits were followed as controls over time. Measurements included hemodynamic parameters and blood gases, ventilation-perfusion (V(A)/Q) distribution (multiple inert gas elimination technique), pulmonary blood flow distribution (fluorescent microspheres), and expired nitric oxide (NO; chemoluminescence). Results Venous gas embolization resulted in a decrease in partial pressure of arterial oxygen (PaO2) and an increase in partial pressure of arterial carbon dioxide (PaCO2), with markedly abnormal overall V(A)/Q distribution and a predominance of high V(A)/Q areas. Pulmonary blood flow distribution was markedly left-skewed, with low-flow areas predominating. Hematocrit decreased from 30+/-1% to 11+/-1% (mean +/- SE) with hemodilution. The alveolar-arterial PO2 (A-aPO2) difference decreased from 375+/-61 mmHg at 30% hematocrit to 218+/-12.8 mmHg at 15% hematocrit, but increased again (301+/-33 mmHg) at 11% hematocrit. In contrast, the A-aPO2 difference increased over time in the control group (P < 0.05 between groups over time). Changes in PaO2 in both groups could be explained in large part by variations in intrapulmonary shunt and mixed venous oxygen saturation (SvO2); however, the improvement in gas exchange with hemodilution was not fully explained by significant changes in V(A)/Q or pulmonary blood flow distributions, as quantitated by the coefficient of variation (CV), fractal dimension, and spatial correlation of blood flow. Expired NO increased with with gas embolization but did not change significantly with time or hemodilution. Conclusions Isovolemic hemodilution results in improved oxygen exchange in rabbits with lung injury induced by gas embolization. The mechanism for this improvement is not clear.

scholarly journals Informativity of blood flow distribution in the precerebral arteries for determining the hemodynamic significance of carotid stenosis

2021 ◽  
Vol 20 (2) ◽  
pp. 45-51
Author(s):  
V. B. Semenyutin ◽  
А. А. Nikiforova ◽  
V. A. Aliev ◽  
G. К. Panuntsev
Keyword(s):  
Blood Flow ◽  
Carotid Artery ◽  
Flow Velocity ◽  
Carotid Stenosis ◽  
Cerebral Artery ◽  
Blood Flow Velocity ◽  
Anterior Cerebral Artery ◽  
Flow Distribution ◽  
External Carotid ◽  
Blood Flow Distribution

Introduction. Conventionally, hemodynamic significance of carotid stenosis is characterized with an increased peak systolic velocity up to 230 cm/s, which corresponds to 70 % carotid stenosis. This does not take into account changes of cerebral hemodynamics or collateral circulation, which can be determined by assessment of blood flow distribution in precerebral arteries. Aim – to evaluate blood flow redistribution in precerebral arteries in patients with critical carotid stenosis. Materials and methods. 40 patients (aged 49–80 y. o.) with critical carotid stenosis were studied (13 patients had 70–79 % stenosis, 11 patients – 80–89 %, and 16 patients – 90–99 % stenosis). Flow velocity index in precerebral arteries was determined with duplex scanning (Vivid e, USA), whereas linear blood flow velocity in intracranial arteries – with transcranial Doppler (MultiDop X, Germany). Results. In 60 % of patients, flow velocity index in ipsilateral carotid artery was reliably decreased (p<0.05). In 49 % of patients flow velocity index in contralateral carotid artery and blood flow velocity in contralateral anterior cerebral artery were reliably increased (p<0.05), as well as linear blood flow velocity in the contralateral anterior cerebral artery. Just in 39 % of patients flow velocity index in ipsilateral vertebral artery and linear blood flow velocity in ipsilateral posterior cerebral artery were increased (p<0.05). In 13 % of cases flow velocity index in the external carotid artery was increased (p<0.05). Conclusion. Thus, critical degree of carotid stenosis does not always indicate its hemodynamic significance. Flow velocity index distribution in precerebral arteries can be used as an additional criterion for assessing hemodynamic significance of carotid stenosis and, along with other indicators, should be taken into account when choosing treatment modality.

scholarly journals Probabilistic Anatomic Mapping of Cerebral Blood Flow Distribution of the Middle Cerebral Artery

2007 ◽  
Vol 49 (1) ◽  
pp. 39-43 ◽  
Author(s):  
S.-J. Kim ◽  
I.-J. Kim ◽  
Y.-K. Kim ◽  
T.-H. Lee ◽  
J. S. Lee ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Middle Cerebral Artery ◽  
Cerebral Artery ◽  
Flow Distribution ◽  
Blood Flow Distribution

Color Doppler Sonographic Evaluation of Collateral Circulation in Patients with Cerebral Aneurysms and the Occlusion of the Brachiocephalic Vessels

Neurosurgery ◽  
2005 ◽  
Vol 57 (6) ◽  
pp. 1117-1126 ◽  
Author(s):  
Wojciech Kaspera ◽  
Henryk Majchrzak ◽  
Piotr Ładziński ◽  
Witold Tomalski
Keyword(s):  
Blood Flow ◽  
Carotid Artery ◽  
Flow Velocity ◽  
Cerebral Aneurysm ◽  
Cerebral Artery ◽  
Blood Flow Velocity ◽  
Collateral Circulation ◽  
Internal Carotid ◽  
Cerebral Aneurysms ◽  
Control Group

Abstract OBJECTIVE: The objective of this study was to assess the collateral circulation and blood flow velocity in arteries forming collateral circulation in patients with cerebral aneurysms and the occlusion of the brachiocephalic vessels. METHODS: Between 1989 and 2004 we examined a group of seven consecutive patients with diagnosed cerebral aneurysm and occlusion of the extracranial artery by means of cerebral angiography, transcranial color-coded sonography (TCCS) and color Doppler sonography of extracranial arteries. The Doppler examination results achieved in this group were compared with the Doppler results of 40 healthy subjects from a control group. RESULTS: Three patients were diagnosed with an occluded innominate artery. In four other cases an occlusion of the extracranial segment of the internal carotid artery was found. The aneurysms were located on intracranial arteries of collateral flow. The innominate artery occlusion resulted in a hemodynamic effect which was a complete vertebral steal and systolic deceleration (in one case) or alternating flow (in two cases) in the right common carotid artery. An additional route of collateral circulation in all these cases led from extracranial carotid branches through the right external carotid artery to the ipsilateral internal carotid artery. In all seven patients, 13 intracranial collateral pathways were examined. In eight of them, including four cases with cerebral aneurysms, an increase in blood flow velocity was observed. In the remaining five cases, including three cases with cerebral aneurysms, the mean blood velocity was within the normal range. The anterior communicating artery (AComA) formed the main intracranial collateral pathway which was found in seven patients, including three patients with diagnosed AComA aneurysm. Blood flow velocity in ipsilateral (on the obstructed side) and contralateral (on the unobstructed side) anterior cerebral artery, as well as pulsatility and resistance indexes in contralateral anterior cerebral and middle cerebral arteries were higher compared with healthy control subjects. In the ipsilateral middle cerebral artery a relative, insignificant decrease of pulsatility and resistance indexes was detected. Ipsilateral and contralateral middle cerebral artery blood flow velocities were lower compared with the control group. CONCLUSION: Occlusion of the brachiocephalic vessels leads to formation of collateral circulation through the circle of Willis and the extracranial collaterals connecting the external and internal carotid arteries. An increase in blood flow velocity is commonly observed in intracranial arteries forming a collateral pathways. In some cases, not excluding arteries with a cerebral aneurysm, the increase in blood flow velocity is insignificant or none at all. This study shows that formation of a cerebral aneurysm is not always related to an increase in the flow velocity of collateral arteries.

Distribution of Renal Blood Flow in Patients with Heart Disease

1972 ◽  
Vol 42 (5) ◽  
pp. 627-634
Author(s):  
D. C. Fluck ◽  
T. R. Evans ◽  
D. C. Siggers ◽  
J. Crawley ◽  
S. A. Srivongse
Keyword(s):  
Blood Flow ◽  
Cardiac Output ◽  
Glomerular Filtration Rate ◽  
Glomerular Filtration ◽  
Renal Blood Flow ◽  
Filtration Rate ◽  
Flow Distribution ◽  
Blood Flow Distribution ◽  
Component Group ◽  
The Mean

1. The renal blood flow distribution has been studied by the Xe washout method in nineteen patients undergoing routine left-sided cardiac catheterization. 2. It was found that there were two separate groups, one in which the washout curve could be analysed by curve stripping into four exponentials, and one in which only three could be detected. 3. The mean cardiac output was found to be lower in the three-component group, whereas the mean glomerular filtration rate did not differ significantly between the two groups. 4. In the four-component group but not in the three-component group, significant linear correlations were detected between cardiac output and glomerular filtration rate, and between glomerular filtration rate and intrarenal blood flow distribution. 5. One suggestion was that the three component distribution of renal blood flow was associated with increasing renal autoregulation and the maintenance of renal function in the presence of a low cardiac output. 6. A second suggestion was that the differences between the three- and four-component group were primarily due to the more intensive diuretic therapy given to the patients in the three-component group.

scholarly journals Fetal Aortic-cerebral Doppler Resistance Index Ratio: An Indicator of Physiologic Blood Flow Distribution

2009 ◽  
Vol 3 (3) ◽  
pp. 91-96
Author(s):  
Zoltán Tóth ◽  
János Aranyosi ◽  
Tamás Deli ◽  
Péter Bettembuk ◽  
Bence Kozma ◽  
...  
Keyword(s):  
Blood Flow ◽  
Middle Cerebral Artery ◽  
Cerebral Artery ◽  
Resistance Index ◽  
Flow Distribution ◽  
Arterial Blood Flow ◽  
Blood Flow Distribution ◽  
Descending Aorta ◽  
Arterial Blood ◽  
Index Ratio

Abstract Identical hemodynamic impedance and constant ratio of the fetal descending aorta and middle cerebral artery of uncomplicated pregnancies at term. Fetal aortic-cerebral Doppler resistance index ratio: An indicator of physiologic blood flow distribution. Objective To interpret the physiologic fetal arterial blood flow distribution by relating the vascular impedance of the fetal descending aorta (DA) and middle cerebral artery (MCA) and to establish the reference ranges for the aortic-cerebral Doppler resistance index ratio (ACRI). Study design Ninety-six patients with uncomplicated pregnancies were recruited for the cross-sectional assessment of the Doppler resistance index (RI) in the fetal DA and MCA between the 38rd and 40th weeks of gestation. The normal ranges of the ACRI were calculated. A cut-off value was designed to facilitate the clinical application of the ACRI. Results Between the 38th and 40th weeks of gestation in normal pregnancies the ACRI of healthy fetuses is constant, the overall mean is: 1.062 (+/– 0.087). A single cut-off value of 1.2 is recommended to assist separating normal and pathologic arterial blood flow patterns. Conclusion The normal ACRI reflects the identical vascular resistance of the descending aorta and the cerebral vessels, which maintains the physiologic fetal central arterial blood flow. Additional clinical studies are necessary to assess the diagnostic efficacy of the abnormal ACRI (>1.2) as a potentially useful marker of the centralized arterial circulation indicating the early stage of fetal hypoxemic jeopardy.

Effect of the larynx on oscillatory flow in the central airways: a model study

1985 ◽  
Vol 59 (1) ◽  
pp. 160-169 ◽  
Author(s):  
A. S. Menon ◽  
M. E. Weber ◽  
H. K. Chang
Keyword(s):  
Oscillatory Flow ◽  
Flow Distribution ◽  
Maximum Flow ◽  
Reynolds Numbers ◽  
Scale Model ◽  
Local Velocity ◽  
Mean Velocity ◽  
Model Study ◽  
Flow Cycle ◽  
The Mean

Measurements were made of the effect of the larynx on the oscillatory flow profiles in a 3:1 scale model of the human central airways. A fixed glottic aperture corresponding to the shape and size at midinspiration was used. Oscillatory airflows at peak Reynolds numbers, similar to those obtained during spontaneous breathing and panting, were studied. The flow distribution to the five lobar bronchi was maintained by distally placed linear resistors. A hot-wire anemometer probe was used to measure the local velocity along two perpendicular diameters at six stations distributed through the model. Near the proximal end of the trachea, the flat velocity profiles at the beginning of the flow cycle peaked at maximum flow because of the jet created by the glottic aperture. This peaked structure was conserved during the latter half of the inspiratory cycle. Close to the carina, the jet had almost dissipated and the entry conditions into the main bronchi corresponded to those in the absence of the laryngeal model. The effect of the glottic aperture on the mean velocity was not felt beyond the carina, and the characteristic skewed profiles seen in oscillatory flows, in the absence of the larynx, were present in the main and lobar bronchi.

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