Dynamic cerebral autoregulation is unrelated to decrease in external carotid artery blood flow during acute hypotension in healthy young men

Ogoh, Shigehiko; Sørensen, Henrik; Hirasawa, Ai; Sasaki, Hiroyuki; Washio, Takuro; Hashimoto, Takeshi; Bailey, Damian Miles; Secher, Niels H.

doi:10.1113/ep085772

Cited by 15 publications

(40 citation statements)

References 33 publications

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“…Our studies also suggest that the intracranial vasculature is 'defended' against acute changes by varying ECA vascular responses during acute central hypovolaemia and hypervolaemia or hypotension or hypertension (Sato et al 2011;Ogoh et al 2013Ogoh et al , 2014Ogoh et al , 2016Hirasawa et al 2016). In addition, Aratow et al (1991) demonstrated that a postural change from 60 deg head-up tilt to −6 deg head-down tilt increased forehead cutaneous flow (ß26%) significantly.…”

Section: Cerebral Blood Flow Distribution During Acute Microgravitymentioning

confidence: 53%

“…MCA) using transcranial Doppler. However, we have recently demonstrated that there is a heterogeneous CBF response in cerebral arteries during several physiological conditions, and the data of these previous studies suggested that these heterogeneous CBF responses might help to maintain circulatory homeostasis in the brain (Sato et al 2011;Ogoh et al 2013Ogoh et al , 2014Ogoh et al , 2016Hirasawa et al 2016). There are two principal arteries that supply blood to the brain, namely the common carotid (CCA) and the vertebral arteries (VA).…”

Section: Introductionmentioning

confidence: 99%

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Internal carotid, external carotid and vertebral artery blood flow responses to 3 days of head‐out dry immersion

Ogoh

Hirasawa

Abreu

et al. 2017

Experimental Physiology

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What is the central question of this study? The extent to which weightlessness associated with a fluid shift from the peripheral to the central circulation influences the blood flow in each cerebral artery remains unknown. The present study was designed to explore the effect of short-term weightlessness conditions on both anterior and posterior cerebral blood flow. What is the main finding and its importance? Short-term weightlessness affects both anterior and posterior cerebral vasculature. However, a heterogeneous cerebral blood flow response in each cerebral artery did not occur during 3 days of dry immersion. We have recently demonstrated that a heterogeneous cerebral blood flow (CBF) response in each cerebral artery might contribute to the maintenance of circulatory homeostasis in the brain. However, the extent to which weightlessness associated with a fluid shift from the peripheral to the central circulation influences the distribution of CBF in each cerebral artery remains unknown. We hypothesized that a dry immersion-induced fluid shift (weightlessness conditions) would cause a heterogeneous CBF response in each cerebral artery. During and after 3 days of dry immersion, the blood flows in the internal carotid (ICA), external carotid (ECA) and vertebral arteries (VA) were measured by Doppler ultrasonography using an 8 MHz linear transducer. Although the 3 days of dry immersion and the 2 days recovery period did not change the blood flow in each cerebral artery, the conductance in both ICA and VA decreased during dry immersion on days 2 and 3 (ICA, 2.95 and 3.23 ml min mmHg ; VA, 1.10 and 1.05 ml min mmHg , respectively) from the baseline (ICA, 3.47 ml min mmHg , P = 0.027; VA, 1.23 ml min mmHg , P = 0.004). In addition, Pearson correlation analysis demonstrated that the 3 days of dry immersion induced a decrease in cardiac output (P = 0.004) that was associated with changes in ICA (P = 0.046) and VA blood flow (P = 0.021), but not ECA blood flow (P = 0.466). These findings suggest that short exposures to weightlessness, acting via a cephalad redistribution of fluid volume and blood flow in the human body, influenced the cerebral vasculature in each cerebral artery but did not cause a heterogeneous CBF response in each cerebral artery.

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Section: Cerebral Blood Flow Distribution During Acute Microgravitymentioning

confidence: 53%

Section: Introductionmentioning

confidence: 99%

Internal carotid, external carotid and vertebral artery blood flow responses to 3 days of head‐out dry immersion

Ogoh

Hirasawa

Abreu

et al. 2017

Experimental Physiology

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“…It is not known what happens to the distribution of Q in spaceflight. The normal response to upright posture is a reduction in splanchnic blood flow (26), while brain blood flow (19) and resting leg blood flow (32) can be reduced. With long-duration spaceflight, blood flow is unchanged from preflight in the femoral and cerebral arteries compared with supine baseline (3).…”

Section: Discussionmentioning

confidence: 99%

Cardiac output by pulse contour analysis does not match the increase measured by rebreathing during human spaceflight

Hughson

Peterson

Yee

et al. 2017

Journal of Applied Physiology

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Pulse contour analysis of the noninvasive finger arterial pressure waveform provides a convenient means to estimate cardiac output (Q̇). The method has been compared with standard methods under a range of conditions but never before during spaceflight. We compared pulse contour analysis with the Modelflow algorithm to estimates of Q̇ obtained by rebreathing during preflight baseline testing and during the final month of long-duration spaceflight in nine healthy male astronauts. By Modelflow analysis, stroke volume was greater in supine baseline than seated baseline or inflight. Heart rate was reduced in supine baseline so that there were no differences in Q̇ by Modelflow estimate between the supine (7.02 ± 1.31 l/min, means ± SD), seated (6.60 ± 1.95 l/min), or inflight (5.91 ± 1.15 l/min) conditions. In contrast, rebreathing estimates of Q̇ increased from seated baseline (4.76 ± 0.67 l/min) to inflight (7.00 ± 1.39 l/min, significant interaction effect of method and spaceflight, < 0.001). Pulse contour analysis utilizes a three-element Windkessel model that incorporates parameters dependent on aortic pressure-area relationships that are assumed to represent the entire circulation. We propose that a large increase in vascular compliance in the splanchnic circulation invalidates the model under conditions of spaceflight. Future spaceflight research measuring cardiac function needs to consider this important limitation for assessing absolute values of Q̇ and stroke volume. Noninvasive assessment of cardiac function during human spaceflight is an important tool to monitor astronaut health. This study demonstrated that pulse contour analysis of finger arterial blood pressure to estimate cardiac output failed to track the 46% increase measured by a rebreathing method. These results strongly suggest that alternative methods not dependent on pulse contour analysis are required to track cardiac function in spaceflight.

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“…Baroreflex acts for example on the total peripheral resistance by modulating sympathetic nerve activity. However, the sympathetic effect on the extracranial vascular bed and the relations between the intracranial and extracranial circulations are not completely understood [4]. A better understanding of the intracranial and extracranial hemodynamics may improve the assessment of the intracranial state by non-invasive, yet superficial tissue dependent, extracranial measurements such as functional Near-Infrared Spectroscopy [5–7] and noninvasive intracranial pressure (ICP) monitoring by strain gauge [8].…”

Section: Introduction and Motivationsmentioning

confidence: 99%

“…The authors in [3,4] recorded the blood flow at the internal (ICA) and external carotid (ECA) arteries during a bout of acute hypotension caused by thigh-cuff inflation-deflation. The ICA blood flow dropped (26.7% in [3], 16.8% in [4]-control) and returned rapidly to baseline levels thanks to CA and baroreflex, showing an overshoot (23.8% in [3], 8.1% in [4]-control) followed by an oscillatory behavior in [3].…”

Section: Introduction and Motivationsmentioning

confidence: 99%

Cerebral hemodynamics: a mathematical model including autoregulation, baroreflex and extracranial peripheral circulation

Linninger

2021

Preprint

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Increasing evidence supports that cerebral autoregulation and mean arterial pressure regulation via baroreflex contribute to cerebral blood flow regulation. It is unclear whether the extracranial vascular bed of the head and neck helps reestablishing cerebral blood flow during changes in mean arterial pressure. Current computational models of cerebral blood flow regulation do not address the relationships between the intracranial and extracranial blood flow dynamics. We present a model of cerebral autoregulation, extracranial peripheral circulation and baroreflex control of heart rate and of peripheral vasculature that was included to the model of intracranial dynamics proposed by Linninger et al. (2009), which incorporates the fully coupled blood, cerebrospinal fluid and brain parenchyma systems. Autoregulation was modelled as being pressure-mediated at the arteries and arterioles and flow-mediated at the microcirculation. During simulations of a bout of acute hypotension, cerebral blood flow returns rapidly to baseline levels with a very small overshoot, whereas the blood flow to the peripheral circulation of the head and neck suffers a prolonged suppression in accordance with experimental evidence. The inclusion of baroreflex regulation at the extracranial vascular bed had a negligible effect on cerebral blood flow regulation during dynamic changes in mean arterial pressure. Moreover, the results suggest that the extracranial blood flow carries only modest information about cerebral blood flow in dynamic situations in which cerebral autoregulation is preserved and mean arterial pressure suffers alterations. This information is likely higher when the autoregulation is impaired. Steady-state cerebral blood flow in the model is kept within normal ranges despite variations in mean arterial pressure from 50 to 175 mmHg. By inputting aortic pressure waves from individuals with increasing arterial rigidity, increasing arterial systolic and pulse pressures, the model predicts the generation of intracranial pressure waves with accordingly increasing peaks and amplitudes.

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Dynamic cerebral autoregulation is unrelated to decrease in external carotid artery blood flow during acute hypotension in healthy young men

Cited by 15 publications

References 33 publications

Internal carotid, external carotid and vertebral artery blood flow responses to 3 days of head‐out dry immersion

Internal carotid, external carotid and vertebral artery blood flow responses to 3 days of head‐out dry immersion

Cardiac output by pulse contour analysis does not match the increase measured by rebreathing during human spaceflight

Cerebral hemodynamics: a mathematical model including autoregulation, baroreflex and extracranial peripheral circulation

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