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  • 1
    ISSN: 1439-6327
    Keywords: Carotid blood flow ; Transcranial Doppler ; Cerebral blood velocities
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We determined middle cerebral artery, common carotid artery and temporal superficial artery Doppler derived flow velocities in ten subjects for 10 min after change in posture. Maximal changes were observed after about 3 min. The 10° head-down tilt position increased blood velocities in the common carotid artery by 13% (SD 4)% (P 〈 0.001), in the middle cerebral artery by,6% (SD 3)% (P 〈 0.001) and in the superficial temporal artery by 70% (SD 26)% (P 〈 0.001). In the standing position, there was an 18% (SD 9)% (P 〈 0.001) decrease in the common carotid blood velocities, with 14% (SD 6)% (P 〈 0.001) and 53% (SD 23)% (P 〈 0.001) reductions in the middle cerebral and superficial temporal artery velocities, respectively. At 9 min after the changes in posture, velocities in the middle cerebral artery were at the value of supine rest, whereas the common carotid blood velocity was not completely restored and deviations in the temporal artery velocity persisted. The data would suggest that cerebral blood flow is regulated with some delay and that such regulation is partially reflected in the common artery blood flow, since changes in a branch of the external carotid artery flow velocity remained.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1439-6327
    Keywords: Key words Intracerebral haemodynamics ; Transcranial Doppler ; Carotid blood flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The intra- and extracerebral Doppler artery blood velocity responses to a 10-mmHg abrupt blood pressure (BP) decrease in ten healthy men were studied. This decrease was obtained using two cuffs placed over both thighs. First, cuffs were inflated to pressures greater than the arterial BP for 5 min. Next, they were deflated to 60 mmHg in order to prevent venous return from the legs. We obtained a decrease in mean arterial BP of from 101 (10) to 90 (10) mmHg [mean (SD), P 〈 0.01] without modifications in the heart rate [HR, 88 (14) beats min−1]. Middle cerebral artery mean blood velocity (MCAmv) decreased immediately from 50 (10) to 42 (12) cm s−1 (P 〈 0.05). Simultaneously, temporal superficial artery mean blood velocity (TSAmv) decreased from 11 (3) to 7 (2) cm s−1 (P 〈 0.05) and common carotid artery blood flow (CCAbf ) decreased from 305 (23) to 233 (33) ml min−1 (P 〈 0.05). After 5 s, MCAmv and CCAbf returned to baseline values, whereas TSAmv [8 (2) cm s−1], mean arterial BP [86 (10) mmHg] remained low and HR increased [92 (12) beats min−1]. TSAmv, BP and HR returned to baseline values in 1 min. These data confirm that cerebral blood flow (CBF) is very rapidly regulated but that blood flow in extracranial territories is not and that it follows the arterial BP changes.
    Type of Medium: Electronic Resource
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