scholarly journals Effect of Head Rotation on Cerebral Blood Velocity in the Prone Position

2012 ◽  
Vol 2012 ◽  
pp. 1-6 ◽  
Author(s):  
Jakob Højlund ◽  
Marie Sandmand ◽  
Morten Sonne ◽  
Teit Mantoni ◽  
Henrik L. Jørgensen ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Prone Position ◽  
Healthy Subjects ◽  
Jugular Vein ◽  
Treated Patient ◽  
Brain Perfusion ◽  
Blood Velocity ◽  
Positive Pressure ◽  
Arterial Blood

Background. The prone position is applied to facilitate surgery of the back and to improve oxygenation in the respirator-treated patient. In particular, with positive pressure ventilation the prone position reduces venous return to the heart and in turn cardiac output (CO) with consequences for cerebral blood flow. We tested in healthy subjects the hypothesis that rotating the head in the prone position reduces cerebral blood flow.Methods. Mean arterial blood pressure (MAP), stroke volume (SV), and CO were determined, together with the middle cerebral artery mean blood velocity (MCAVmean) and jugular vein diameters bilaterally in 22 healthy subjects in the prone position with the head centered, respectively, rotated sideways, with and without positive pressure breathing (10 cmH2O).Results. The prone position reduced SV (by5.4±1.5%;P<0.05) and CO (by2.3±1.9%), and slightly increased MAP (from78±3to80±2 mmHg) as well as bilateral jugular vein diameters, leaving MCAVmeanunchanged. Positive pressure breathing in the prone position increased MAP (by3.6±0.8 mmHg) but further reduced SV and CO (by9.3±1.3% and7.2±2.4% below baseline) while MCAVmeanwas maintained. The head-rotated prone position with positive pressure breathing augmented MAP further (87±2 mmHg) but not CO, narrowed both jugular vein diameters, and reduced MCAVmean(by8.6±3.2%).Conclusion. During positive pressure breathing the prone position with sideways rotated head reduces MCAVmean~10% in spite of an elevated MAP. Prone positioning with rotated head affects both CBF and cerebrovenous drainage indicating that optimal brain perfusion requires head centering.

scholarly journals Comparison of cerebral blood flow measurement with [15O]-water positron emission tomography and arterial spin labeling magnetic resonance imaging: A systematic review

2016 ◽  
Vol 36 (5) ◽  
pp. 842-861 ◽  
Author(s):  
Audrey P Fan ◽  
Hesamoddin Jahanian ◽  
Samantha J Holdsworth ◽  
Greg Zaharchuk
Keyword(s):  
Positron Emission Tomography ◽  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Arterial Spin Labeling ◽  
Brain Perfusion ◽  
Spin Labeling ◽  
Emission Tomography ◽  
Flow Measurements ◽  
Arterial Blood ◽  
Positron Emission

Noninvasive imaging of cerebral blood flow provides critical information to understand normal brain physiology as well as to identify and manage patients with neurological disorders. To date, the reference standard for cerebral blood flow measurements is considered to be positron emission tomography using injection of the [15O]-water radiotracer. Although [15O]-water has been used to study brain perfusion under normal and pathological conditions, it is not widely used in clinical settings due to the need for an on-site cyclotron, the invasive nature of arterial blood sampling, and experimental complexity. As an alternative, arterial spin labeling is a promising magnetic resonance imaging technique that magnetically labels arterial blood as it flows into the brain to map cerebral blood flow. As arterial spin labeling becomes more widely adopted in research and clinical settings, efforts have sought to standardize the method and validate its cerebral blood flow values against positron emission tomography-based cerebral blood flow measurements. The purpose of this work is to critically review studies that performed both [15O]-water positron emission tomography and arterial spin labeling to measure brain perfusion, with the aim of better understanding the accuracy and reproducibility of arterial spin labeling relative to the positron emission tomography reference standard.

scholarly journals Utilization of the repeated squat-stand model for studying the directional behavior of the cerebral pressure-flow relationship

2020 ◽  
Author(s):  
Lawrence Labrecque ◽  
Jonathan Smirl ◽  
Patrice Brassard
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Mean Arterial Pressure ◽  
Cerebral Autoregulation ◽  
Healthy Subjects ◽  
Blood Velocity ◽  
Pressure Flow ◽  
Flow Changes ◽  
Relative Change ◽  
Dynamic Cerebral Autoregulation

Hysteresis in the cerebral pressure-flow relationship describes the superior ability of the cerebrovasculature to buffer cerebral blood flow changes when mean arterial pressure (MAP) acutely increases compared to when it decreases. This phenomenon can be evaluated by comparing the relative change in middle cerebral artery mean blood velocity (MCAv) per relative change in MAP (%ΔMCAv/%ΔMAP) during either acute increases or decreases in MAP induced by repeated squat-stands (RSS). However, no real baseline can be employed for this particular protocol as there is no true stable reference point. Herein, we characterized the %ΔMCAv/%ΔMAP metric using the greatest MAP oscillations induced by RSS without using an independent baseline value. We also examined whether %ΔMCAv/%ΔMAP during each RSS transition were comparable between each other over the 5-min period. %ΔMCAv/%ΔMAP was calculated using the minimum to maximum MCAv and MAP for each RSS performed at 0.05 Hz and 0.10 Hz. We compared averaged %ΔMCAv/%ΔMAP during MAP increases and decreases in 74 healthy subjects [9 women; 32 ± 13 years]. %ΔMCAv/%ΔMAP was lower for MAP increases than MAP decreases (0.05 Hz: 1.25 ± 0.22 vs. 1.35 ± 0.27 %/%, p<0.0001; 0.10Hz: 1.31 ± 0.24 vs. 1.60 ± 0.50 %/%, p<0.0001). For both frequency and MAP direction, time during RSS had no effect on %ΔMCAv/%ΔMAP. This novel analytical method supports the use of the RSS model to evaluate the directional behavior of the pressure-flow relationship. These results contribute to the importance of considering the direction of MAP changes when evaluating dynamic cerebral autoregulation.

Abstract TMP103: New Blood Velocity Indices Can Improve the Accuracy of Transcranial Doppler to Detect Vasospasm After Subarachnoid Hemorrhage

Stroke ◽  
2016 ◽  
Vol 47 (suppl_1) ◽  
Author(s):  
Jaiyoung Ryu ◽  
Xiao Hu ◽  
Shawn C Shadden
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Subarachnoid Hemorrhage ◽  
Transcranial Doppler ◽  
Cerebral Autoregulation ◽  
Blood Velocity ◽  
Arterial Blood Flow ◽  
Flow Rates ◽  
Arterial Blood ◽  
Basilar Arteries

Background and Objectives: Early diagnosis of vasospasm after subarachnoid hemorrhage (SAH) can prompt aggressive treatment and improve neurological outcomes. Transcranial Doppler (TCD) is the only diagnosis modality that is noninvasive and available bedside. The purpose of this study was to numerically evaluate the relevance of various blood velocity indices in detection of unbalanced cerebral blood flow due to vasospasm, and to improve the accuracy of diagnosis using TCD. Methods: We employed a well-validated numerical model of arterial blood flow coupled with a sophisticated intracranial model to generate a cerebral blood flow database. Anterior (MCA and/or ACA) and posterior (PCA and/or basilar arteries) vasospasms were considered under normal and impaired cerebral autoregulation conditions. For each case, mean blood velocities and their ratios between ipsilateral and contralateral, downstream and upstream, and anterior and posterior arteries were monitored during the progress of vasospasm. Results: Blood velocities at vasospastic arterial segments demonstrated non-monotonic behavior, i.e. the velocities increased initially with mild and moderate vasospasm, however further vasospasm leads to decreasing values. This may lead to false-negative decisions clinically. Blood flow rates, however, decreased monotonically at the affected arteries. Blood velocities upstream of the vasospastic artery decreased in proportion to the blood flow rates (e.g. for MCA vasospasm, 30% and 20% reduction at ICA and CCA). For all vasospasm locations considered, normalization of velocities by upstream and contralateral velocities provided more robust detection. Moreover, the improvements were most compelling in cases with impaired cerebral autoregulation. Conclusions: The velocity indices and diagnosis strategy proposed in this study can improve the accuracy of TCD diagnosis for cerebral vasospasm. These indices are particularly effective in cases of severe vasospasm where traditional indices (e.g. absolute velocities, Lindegaard index) become problematic.

scholarly journals The Phosphodiesterase 5 Inhibitor Sildenafil Has No Effect on Cerebral Blood Flow or Blood Velocity, but Nevertheless Induces Headache in Healthy Subjects

2002 ◽  
Vol 22 (9) ◽  
pp. 1124-1131 ◽  
Author(s):  
Christina Kruuse ◽  
Lars Lykke Thomsen ◽  
Torsten Bjørn Jacobsen ◽  
Jes Olesen
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Middle Cerebral Artery ◽  
Cerebral Artery ◽  
Healthy Subjects ◽  
Blood Velocity ◽  
Emission Computed Tomography ◽  
Phosphodiesterase 5

Cyclic nucleotides are important hemodynamic regulators in many tissues. Glyceryl trinitrate markedly dilates large cerebral arteries and increases cGMP. Here, the authors study the effect of sildenafil, a selective inhibitor of cGMP-hydrolyzing phosphodiesterase 5 on cerebral hemodynamics and headache induction. Ten healthy subjects were included in a double-blind, placebo-controlled crossover study where placebo or sildenafil 100 mg (highest therapeutic dose) were administered on two separate days. Blood velocity in the middle cerebral artery (Vmca) was recorded by transcranial Doppler, and regional cerebral blood flow in the perfusion area of the middle cerebral artery (rCBFmca) was measured using single photon emission computed tomography and 133xenon inhalation. Radial and temporal artery diameters were studied using high-frequency ultrasound. Blood pressure and heart rate were recorded repeatedly. Headache responses and tenderness of pericranial muscles were scored verbally. Sildenafil caused no significant changes in rCBFmca, Vmca, or in temporal or radial artery diameter, but heart rate increased and diastolic blood pressure decreased significantly compared to placebo. Despite the lack of cerebral arterial dilatation, sildenafil caused significantly more headache than placebo. The present results show that sildenafil 100 mg does not dilate cerebral or extracerebral arteries but nevertheless causes headache, which may be attributed to nonvascular mechanisms.

Headache at high altitude is not related to internal carotid arterial blood velocity

1985 ◽  
Vol 59 (3) ◽  
pp. 909-915 ◽  
Author(s):  
J. T. Reeves ◽  
L. G. Moore ◽  
R. E. McCullough ◽  
R. G. McCullough ◽  
G. Harrison ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
High Altitude ◽  
Internal Carotid ◽  
Blood Velocity ◽  
Base Line ◽  
Primary Role ◽  
Arterial Blood ◽  
End Tidal ◽  
Carotid Arterial

The cause of headache in persons going to high altitude is unknown. Relatively severe hypoxemia in susceptible subjects could induce large increases in cerebral blood flow that then could initiate the headache. Thus we measured noninvasively, by Doppler ultrasound, changes in internal carotid arterial blood velocity (velocity) in 12 subjects in Denver (1,600 m) and repeatedly up to 7 h at a simulated altitude of 4,800 m (barometric pressure = 430 Torr). Six subjects, selected because of prior history of high-altitude headache, developed comparatively severe headache at 4,800 m, and four subjects, without such history, remained well. Two subjects developed moderate headache. Velocity at 4,800 m did not correlate with symptom development, arterial O2 saturation, or end-tidal PCO2. Also, neither velocity nor blood pressure was consistently elevated above the Denver base-line values. During measurements of hypercapnic ventilatory response in Denver, velocity increased linearly with end-tidal PCO2, confirming that our Doppler method could demonstrate an increase. Also, 30 min of isocapnic or poikilocapnic hypoxia caused small increases in velocity (+8 and +6%) during the base-line measurement at low altitude. Although even a small increase in cerebral perfusion could contribute to headache symptoms at high altitude, cerebral blood flow does not appear to play a primary role.

scholarly journals The cerebrocardiovascular response to periodic squat-stand maneuvers in healthy subjects: a time-domain analysis

2017 ◽  
Vol 313 (6) ◽  
pp. H1240-H1248 ◽  
Author(s):  
Sam C. Barnes ◽  
Naomi Ball ◽  
Victoria Joanna Haunton ◽  
Thompson G. Robinson ◽  
Ronney B. Panerai
Keyword(s):  
Heart Rate ◽  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Healthy Subjects ◽  
Function Analysis ◽  
Time Domain Analysis ◽  
Blood Velocity ◽  
Potential Contribution ◽  
Transfer Function Analysis ◽  
Cerebral Blood Velocity

Squat-stand maneuvers (SSMs) have been used to improve the coherence of transfer function analysis (TFA) estimates during the assessment of dynamic cerebral autoregulation (dCA). There is a need to understand the influence of peripheral changes resulting from SSMs on cerebral blood flow, which might confound estimates of dCA. Healthy subjects ( n = 29) underwent recordings at rest (5-min standing) and 15 SSMs (0.05 Hz). Heart rate (three-lead ECG), end-tidal CO2 (capnography), blood pressure (Finometer), cerebral blood velocity (CBV; transcranial Doppler, middle cerebral artery), and the angle of the thigh (tilt sensor) were measured continuously. The response of CBV to SSMs was decomposed into the relative contributions of mean arterial pressure (MAP), resistance-area product (RAP), and critical closing pressure (CrCP). Upon squatting, a rise in MAP (83.6 ± 21.1% contribution) was followed by increased CBV. A dCA response could be detected, determined by adjustments in RAP and CrCP (left hemisphere) with peak contributions of 24.8 ± 12.7% and 27.4 ± 22.8%, respectively, at different times during SSMs. No interhemispheric differences were detected. During standing, the contributions of MAP, RAP, and CrCP changed considerably. In conclusion, the changes of CBV subcomponents during repeated SSMs indicate a complex response of CBV to SSMs that can only be partially explained by myogenic mechanisms. More work is needed to clarify the potential contribution of other cofactors, such as breath-to-breath changes in Pco2, heart rate, stroke volume, and the neurogenic component of dCA. NEW & NOTEWORTHY Here, we describe the different contributions to the cerebral blood flow response after squat-stand maneuvers. Furthermore, we demonstrate the complex interaction of peripheral and cerebral parameters for the first time. Moreover, we show that the cerebral blood velocity response to squatting is likely to include a significant metabolic component.

scholarly journals Sustained Inflation Reduces Pulmonary Blood Flow during Resuscitation with an Intact Cord

Children ◽  
2021 ◽  
Vol 8 (5) ◽  
pp. 353
Author(s):  
Jayasree Nair ◽  
Lauren Davidson ◽  
Sylvia Gugino ◽  
Carmon Koenigsknecht ◽  
Justin Helman ◽  
...  
Keyword(s):  
Blood Flow ◽  
Perinatal Asphyxia ◽  
Arterial Blood Flow ◽  
Positive Pressure ◽  
Optimal Timing ◽  
Delayed Cord Clamping ◽  
Arterial Blood ◽  
Cord Clamping ◽  
Sustained Inflation ◽  
Near Term

The optimal timing of cord clamping in asphyxia is not known. Our aims were to determine the effect of ventilation (sustained inflation–SI vs. positive pressure ventilation–V) with early (ECC) or delayed cord clamping (DCC) in asphyxiated near-term lambs. We hypothesized that SI with DCC improves gas exchange and hemodynamics in near-term lambs with asphyxial bradycardia. A total of 28 lambs were asphyxiated to a mean blood pressure of 22 mmHg. Lambs were randomized based on the timing of cord clamping (ECC—immediate, DCC—60 s) and mode of initial ventilation into five groups: ECC + V, ECC + SI, DCC, DCC + V and DCC + SI. The magnitude of placental transfusion was assessed using biotinylated RBC. Though an asphyxial bradycardia model, 2–3 lambs in each group were arrested. There was no difference in primary outcomes, the time to reach baseline carotid blood flow (CBF), HR ≥ 100 bpm or MBP ≥ 40 mmHg. SI reduced pulmonary (PBF) and umbilical venous (UV) blood flow without affecting CBF or umbilical arterial blood flow. A significant reduction in PBF with SI persisted for a few minutes after birth. In our model of perinatal asphyxia, an initial SI breath increased airway pressure, and reduced PBF and UV return with an intact cord. Further clinical studies evaluating the timing of cord clamping and ventilation strategy in asphyxiated infants are warranted.

scholarly journals Renal arterial blood flow measurement by breath-held MRI: Accuracy in phantom scans and reproducibility in healthy subjects

2010 ◽  
Vol 63 (4) ◽  
pp. 940-950 ◽  
Author(s):  
Samuel Dambreville ◽  
Arlene B. Chapman ◽  
Vicente E. Torres ◽  
Bernard F. King ◽  
Ashley K. Wallin ◽  
...  
Keyword(s):  
Blood Flow ◽  
Healthy Subjects ◽  
Flow Measurement ◽  
Arterial Blood Flow ◽  
Blood Flow Measurement ◽  
Arterial Blood

scholarly journals Examination of Potential Mechanisms in the Enhancement of Cerebral Blood Flow by Hypoglycemia and Pharmacological Doses of Deoxyglucose

1997 ◽  
Vol 17 (1) ◽  
pp. 54-63 ◽  
Author(s):  
Naoaki Horinaka ◽  
Nicole Artz ◽  
Jane Jehle ◽  
Shinichi Takahashi ◽  
Charles Kennedy ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Glucose Metabolism ◽  
Plasma Glucose ◽  
Plasma Lactate ◽  
Insulin Hypoglycemia ◽  
Glucose Levels ◽  
Arterial Blood ◽  
Arterial Plasma

Cerebral blood flow (CBF) rises when the glucose supply to the brain is limited by hypoglycemia or glucose metabolism is inhibited by pharmacological doses of 2-deoxyglucose (DG). The present studies in unanesthetized rats with insulin-induced hypoglycemia show that the increases in CBF, measured with the [14C]iodoantipyrine method, are relatively small until arterial plasma glucose levels fall to 2.5 to 3.0 m M, at which point CBF rises sharply. A direct effect of insulin on CBF was excluded; insulin administered under euglycemic conditions maintained by glucose injections had no effects on CBF. Insulin administration raised plasma lactate levels and decreased plasma K+ and HCO3– concentrations and arterial pH. These could not, however, be related to the increased CBF because insulin under euglycemic conditions had similar effects without affecting CBF; furthermore, the inhibition of brain glucose metabolism with pharmacological doses (200 mg/kg intravenously) of DG increased CBF, just like insulin hypoglycemia, without altering plasma lactate and K+ levels and arterial blood gas tensions and pH. Nitric oxide also does not appear to mediate the increases in CBF. Chronic blockade of nitric oxide synthase activity by twice daily i.p. injections of NG-nitro-L-arginine methyl ester for 4 days or acutely by a single i.v. injection raised arterial blood pressure and lowered CBF in normoglycemic, hypoglycemic, and DG-treated rats but did not significantly reduce the increases in CBF due to insulin-induced hypoglycemia (arterial plasma glucose levels, 2.5-3 m M) or pharmacological doses of deoxyglucose.

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