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Blood flow in internal carotid and vertebral arteries during orthostatic stress

Kohei Sato1, James P Fisher, Thomas Seifert

  • 1Research Institute of Physical Fitness, Japan Women's College of Physical Education, Tokyo, Japan. ksato@jwcpe.ac.jp

Experimental Physiology
|June 13, 2012
PubMed

Insights

Orthostatic stress causes different changes in blood flow within the internal carotid arteries (ICA) and vertebral arteries (VA). Cerebral autoregulation is also impaired during head-up tilt, particularly in the VA.

Area of Science:

  • Physiology
  • Neuroscience
  • Cardiovascular Science

Background:

  • Orthostatic stress, like head-up tilt, can affect blood flow to the brain.
  • Regional differences in cerebral blood flow responses to orthostatic stress are not well understood.

Purpose of the Study:

  • To investigate regional differences in cerebral blood flow (CBF) and dynamic cerebral autoregulation (CA) in the internal carotid arteries (ICA) and vertebral arteries (VA) during orthostatic stress.

Main Methods:

  • Six healthy young men underwent 60-degree head-up tilt (HUT).
  • Blood flow in the ICA and VA was measured using Doppler ultrasonography.
  • Dynamic CA was assessed via the rate of regulation (RoR) during thigh-cuff release-induced hypotension in supine and HUT positions.

Main Results:

  • HUT decreased ICA blood flow (-9.4%) but did not change ICA conductance.
  • VA blood flow remained unchanged, while VA conductance increased (+12.9%) during HUT.
  • Dynamic CA, measured by RoR, was attenuated in both ICA and VA during HUT, with a more significant reduction in the VA.

Conclusions:

  • Orthostatic stress induces regional variations in CBF between the ICA and VA.
  • Dynamic CA is impaired during HUT, with differential effects on the ICA and VA.
  • These findings highlight distinct cerebrovascular responses to orthostatic challenges in major brain arteries.

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