scholarly journals Assessment of Functional Hemispheric Asymmetry by Bilateral Simultaneous Cerebral Blood Flow Velocity Monitoring

1997 ◽  
Vol 17 (5) ◽  
pp. 577-585 ◽  
Author(s):  
Jürgen Klingelhöfer ◽  
Gernot Matzander ◽  
Dirk Sander ◽  
Jens Schwarze ◽  
Henning Boecker ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Blood Flow ◽  
Flow Velocity ◽  
Transcranial Doppler ◽  
Spatial Task ◽  
Hemispheric Dominance ◽  
Left And Right ◽  
End Tidal ◽  
Overt Speech

The aim of this study was to investigate side-to-side differences of simultaneously measured middle cerebral artery (MCA) blood flow velocities during various hemisphere-specific tasks. Using a transcranial Doppler device, flow velocity changes of 24 healthy, right-handed subjects were monitored simultaneously in the left and right MCA during different hemisphere-specific tasks. Mean flow velocity (MFV) curves were averaged for each individual subject and task. Simultaneously, heart rate, blood pressure and end-tidal carbon dioxide (CO2) were measured in a subgroup of six subjects. When compared with the resting state, all stimuli produced significant ( p < 0.001) bilateral MFV increases, ranging from 2.5–9.2%. A lateralization of MFV increases with a significantly ( p < 0.001) more pronounced increase in MFV in the hemisphere contralateral to the performing hand was observed both during simple sequential finger movements and a complex spatial task. During the complex spatial task, consistently higher MFV increases were observed in the right MCA ( p < 0.001), regardless of the side of task performance. Recognition of pictorial material presented as part of a memory task, also resulted in a side-to-side difference of respective MFV increases (right > left, p < 0.001), whereas memorization did not. Whereas bilateral MFV elevations observed during stimulation with white noise were only discrete and not lateralized, exposure to overt speech produced significantly higher ( p < 0.001) MFV increases in the left MCA. The time course of the MFV reaction showed a rapid increase with an initial maximum after 4–5 s. Heart rate, blood pressure, and end-tidal CO2 showed only subtle changes during the stimulation periods. In conclusion, the observed side-to-side differences of MFV reaction in the left and right MCA concur with current functional imaging data. Bilateral simultaneous repetitive transcranial Doppler monitoring is a sensitive method to detect cerebral perfusion asymmetries caused by hemisphere-specific activation, and thus may be helpful for noninvasive assessment of hemispheric dominance for language.

Direct Cerebral Vasodilatory Effects of Sevoflurane and Isoflurane 

1999 ◽  
Vol 91 (3) ◽  
pp. 677-677 ◽  
Author(s):  
Basil F. Matta ◽  
Karen J. Heath ◽  
Kate Tipping ◽  
Andrew C. Summors
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Middle Cerebral Artery ◽  
Flow Velocity ◽  
Cerebral Artery ◽  
Blood Flow Velocity ◽  
End Tidal

Background The effect of volatile anesthetics on cerebral blood flow depends on the balance between the indirect vasoconstrictive action secondary to flow-metabolism coupling and the agent's intrinsic vasodilatory action. This study compared the direct cerebral vasodilatory actions of 0.5 and 1.5 minimum alveolar concentration (MAC) sevoflurane and isoflurane during an propofol-induced isoelectric electroencephalogram. Methods Twenty patients aged 20-62 yr with American Society of Anesthesiologists physical status I or II requiring general anesthesia for routine spinal surgery were recruited. In addition to routine monitoring, a transcranial Doppler ultrasound was used to measure blood flow velocity in the middle cerebral artery, and an electroencephalograph to measure brain electrical activity. Anesthesia was induced with propofol 2.5 mg/kg, fentanyl 2 micro/g/kg, and atracurium 0.5 mg/kg, and a propofol infusion was used to achieve electroencephalographic isoelectricity. End-tidal carbon dioxide, blood pressure, and temperature were maintained constant throughout the study period. Cerebral blood flow velocity, mean blood pressure, and heart rate were recorded after 20 min of isoelectric encephalogram. Patients were then assigned to receive either age-adjusted 0.5 MAC (0.8-1%) or 1.5 MAC (2.4-3%) end-tidal sevoflurane; or age-adjusted 0.5 MAC (0.5-0.7%) or 1.5 MAC (1.5-2%) end-tidal isoflurane. After 15 min of unchanged end-tidal concentration, the variables were measured again. The concentration of the inhalational agent was increased or decreased as appropriate, and all measurements were repeated again. All measurements were performed before the start of surgery. An infusion of 0.01% phenylephrine was used as necessary to maintain mean arterial pressure at baseline levels. Results Although both agents increased blood flow velocity in the middle cerebral artery at 0.5 and 1.5 MAC, this increase was significantly less during sevoflurane anesthesia (4+/-3 and 17+/-3% at 0.5 and 1.5 MAC sevoflurane; 19+/-3 and 72+/-9% at 0.5 and 1.5 MAC isoflurane [mean +/- SD]; P&lt;0.05). All patients required phenylephrine (100-300 microg) to maintain mean arterial pressure within 20% of baseline during 1.5 MAC anesthesia. Conclusions In common with other volatile anesthetic agents, sevoflurane has an intrinsic dose-dependent cerebral vasodilatory effect. However, this effect is less than that of isoflurane.

scholarly journals Adenosine receptor-dependent signaling is not obligatory for normobaric and hypobaric hypoxia-induced cerebral vasodilation in humans

2017 ◽  
Vol 122 (4) ◽  
pp. 795-808 ◽  
Author(s):  
Ryan L. Hoiland ◽  
Anthony R. Bain ◽  
Michael M. Tymko ◽  
Mathew G. Rieger ◽  
Connor A. Howe ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Blood Flow ◽  
Cerebral Blood Flow ◽  
High Altitude ◽  
Sea Level ◽  
Adenosine Receptor ◽  
Hypobaric Hypoxia ◽  
End Tidal ◽  
Double Blinded

Hypoxia increases cerebral blood flow (CBF) with the underlying signaling processes potentially including adenosine. A randomized, double-blinded, and placebo-controlled design, was implemented to determine if adenosine receptor antagonism (theophylline, 3.75 mg/Kg) would reduce the CBF response to normobaric and hypobaric hypoxia. In 12 participants the partial pressures of end-tidal oxygen ([Formula: see text]) and carbon dioxide ([Formula: see text]), ventilation (pneumotachography), blood pressure (finger photoplethysmography), heart rate (electrocardiogram), CBF (duplex ultrasound), and intracranial blood velocities (transcranial Doppler ultrasound) were measured during 5-min stages of isocapnic hypoxia at sea level (98, 90, 80, and 70% [Formula: see text]). Ventilation, [Formula: see text] and [Formula: see text], blood pressure, heart rate, and CBF were also measured upon exposure (128 ± 31 min following arrival) to high altitude (3,800 m) and 6 h following theophylline administration. At sea level, although the CBF response to hypoxia was unaltered pre- and postplacebo, it was reduced following theophylline ( P < 0.01), a finding explained by a lower [Formula: see text] ( P < 0.01). Upon mathematical correction for [Formula: see text], the CBF response to hypoxia was unaltered following theophylline. Cerebrovascular reactivity to hypoxia (i.e., response slope) was not different between trials, irrespective of [Formula: see text]. At high altitude, theophylline ( n = 6) had no effect on CBF compared with placebo ( n = 6) when end-tidal gases were comparable ( P > 0.05). We conclude that adenosine receptor-dependent signaling is not obligatory for cerebral hypoxic vasodilation in humans. NEW & NOTEWORTHY The signaling pathways that regulate human cerebral blood flow in hypoxia remain poorly understood. Using a randomized, double-blinded, and placebo-controlled study design, we determined that adenosine receptor-dependent signaling is not obligatory for the regulation of human cerebral blood flow at sea level; these findings also extend to high altitude.

Case 16: Autonomic Failure or Postural Tachycardia Syndrome?

2019 ◽  
pp. 120-124
Author(s):  
Peter Novak
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Flow Velocity ◽  
Blood Flow Velocity ◽  
Cerebral Blood Flow Velocity ◽  
Postural Tachycardia Syndrome ◽  
Postural Tachycardia ◽  
Transient Elevation

Small fiber neuropathy is associated with adrenergic failure. Anxiety is common and occasionally can be identified as a transient elevation of heart rate, blood pressure, and cerebral blood flow velocity.

scholarly journals Postural hypocapnic hyperventilation is associated with enhanced peripheral vasoconstriction in postural tachycardia syndrome with normal supine blood flow

2006 ◽  
Vol 291 (2) ◽  
pp. H904-H913 ◽  
Author(s):  
Julian M. Stewart ◽  
Marvin S. Medow ◽  
Neil S. Cherniack ◽  
Benjamin H. Natelson
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Blood Flow ◽  
Blood Volume ◽  
Peripheral Resistance ◽  
Impedance Plethysmography ◽  
Postural Tachycardia Syndrome ◽  
Peripheral Vasoconstriction ◽  
Postural Tachycardia ◽  
End Tidal

Previous investigations have demonstrated a subset of postural tachycardia syndrome (POTS) patients characterized by normal peripheral resistance and blood volume while supine but thoracic hypovolemia and splanchnic blood pooling while upright secondary to splanchnic hyperemia. Such “normal-flow” POTS patients often demonstrate hypocapnia during orthostatic stress. We studied 20 POTS patients (14–23 yr of age) and compared them with 10 comparably aged healthy volunteers. We measured changes in heart rate, blood pressure, heart rate and blood pressure variability, arm and leg strain-gauge occlusion plethysmography, respiratory impedance plethysmography calibrated against pneumotachography, end-tidal partial pressure of carbon dioxide (PetCO2), and impedance plethysmographic indexes of blood volume and blood flow within the thoracic, splanchnic, pelvic (upper leg), and lower leg regional circulations while supine and during upright tilt to 70°. Ten POTS patients demonstrated significant hyperventilation and hypocapnia (POTSHC) while 10 were normocapnic with minimal increase in postural ventilation, comparable to control. While relative splanchnic hypervolemia and hyperemia occurred in both POTS groups compared with controls, marked enhancement in peripheral vasoconstriction occurred only in POTSHC and was related to thoracic blood flow. Variability indexes suggested enhanced sympathetic activation in POTSHC compared with other subjects. The data suggest enhanced cardiac and peripheral sympathetic excitation in POTSHC.

scholarly journals Modeling of Hemodynamics in a Vascular Bioprosthesis

2021 ◽  
Vol 16 (1) ◽  
pp. 15-28
Author(s):  
P. Onishchenko ◽  
Yu. Zakharov ◽  
V. Borisov ◽  
K. Klyshnikov ◽  
E. Ovcharenko ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Blood Flow ◽  
Flow Velocity ◽  
Flow Structure ◽  
Numerical Comparison ◽  
Vascular Bed ◽  
Inner Surface ◽  
Implantation Method ◽  
Complicated Task

The study of blood flow in vascular bioprostheses is a rather complicated task, since the shape of the inner surface of the bioprosthesis is variable, due to xenogenic origin. Because of this, vortex zones can occur inside the vascular bioprosthesis. In addition, the flow structure may contain sections where the flow velocity is abnormally high. It is all the more difficult to assess the nature of the course when using this vascular bioprosthesis as a shunt. A numerical comparison of the blood flow in a bioprosthesis connected to the main vascular bed using the «end-to-end» and «end-to-side» methods (bypass) taking into account the heart rate and blood pressure was performed. It is shown that, due to the nonlinearity of the initial bioprosthesis geometry, the implantation method affects the blood flow. Because of this, vortex zones arise and, with certain combinations of parameters, the effects of «separation» of vortices.

Case 31: Hypocapnic Cerebral Hypoperfusion with an Artifact

2019 ◽  
pp. 194-197
Author(s):  
Peter Novak
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Flow Velocity ◽  
Blood Flow Velocity ◽  
Cerebral Blood Flow Velocity ◽  
Cerebral Hypoperfusion ◽  
Autonomic Functions ◽  
Raw Data

In this patient, the initial decline in blood pressure at the tilt onset was physiologic since it was accompanied by the decline in cerebral blood flow velocity and heart rate responses. The testing revealed normal autonomic functions. It is important always to check the raw data. Blood pressure from the finger cuff is not always accurate.

scholarly journals Systemic hypoxia and vasoconstrictor responsiveness in exercising human muscle

2006 ◽  
Vol 101 (5) ◽  
pp. 1343-1350 ◽  
Author(s):  
Brad W. Wilkins ◽  
William G. Schrage ◽  
Zhong Liu ◽  
Kellie C. Hancock ◽  
Michael J. Joyner
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Blood Flow ◽  
Forearm Blood Flow ◽  
Minute Ventilation ◽  
Exercise Bout ◽  
Dependent Manner ◽  
Forearm Exercise ◽  
End Tidal ◽  
Hypoxic Exercise

Exercise blunts sympathetic α-adrenergic vasoconstriction (functional sympatholysis). We hypothesized that sympatholysis would be augmented during hypoxic exercise compared with exercise alone. Fourteen subjects were monitored with ECG and pulse oximetry. Brachial artery and antecubital vein catheters were placed in the nondominant (exercising) arm. Subjects breathed hypoxic gas to titrate arterial O2 saturation to 80% while remaining normocapnic via a rebreath system. Baseline and two 8-min bouts of rhythmic forearm exercise (10 and 20% of maximum) were performed during normoxia and hypoxia. Forearm blood flow, blood pressure, heart rate, minute ventilation, and end-tidal CO2 were measured at rest and during exercise. Vasoconstrictor responsiveness was determined by responses to intra-arterial tyramine during the final 3 min of rest and each exercise bout. Heart rate was higher during hypoxia ( P < 0.01), whereas blood pressure was similar ( P = 0.84). Hypoxic exercise potentiated minute ventilation compared with normoxic exercise ( P < 0.01). Forearm blood flow was higher during hypoxia compared with normoxia at rest (85 ± 9 vs. 66 ± 7 ml/min), at 10% exercise (276 ± 33 vs. 217 ± 27 ml/min), and at 20% exercise (464 ± 32 vs. 386 ± 28 ml/min; P < 0.01). Arterial epinephrine was higher during hypoxia ( P < 0.01); however, venoarterial norepinephrine difference was similar between hypoxia and normoxia before ( P = 0.47) and during tyramine administration ( P = 0.14). Vasoconstriction to tyramine (%decrease from pretyramine values) was blunted in a dose-dependent manner with increasing exercise intensity ( P < 0.01). Interestingly, vasoconstrictor responsiveness tended to be greater ( P = 0.06) at rest (−37 ± 6% vs. −33 ± 6%), at 10% exercise (−27 ± 5 vs. −22 ± 4%), and at 20% exercise (−22 ± 5 vs. −14 ± 4%) between hypoxia and normoxia, respectively. Thus sympatholysis is not augmented by moderate hypoxia nor does it contribute to the increased blood flow during hypoxic exercise.

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