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Syncope, cerebral perfusion, and oxygenation.

Johannes J Van Lieshout1, Wouter Wieling, John M Karemaker

  • 1Cardiovascular Research Institute Amsterdam and Departments of Medicine and Physiology, Academic Medical Center, University of Amsterdam, 1105 AZ Amsterdam, The Netherlands. j.j.vanlieshout@amc.uva.nl

Journal of Applied Physiology (Bethesda, Md. : 1985)
|February 7, 2003
PubMed
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Standing challenges the brain

Area of Science:

  • Neuroscience
  • Cardiovascular Physiology
  • Autonomic Nervous System Function

Background:

  • Upright posture reduces blood flow to the brain, challenging cerebral autoregulation (CA).
  • Syncope (fainting) is linked to compromised cerebral blood flow (CBF) and oxygenation.
  • Muscle activity is crucial for maintaining blood volume and preventing syncope.

Purpose of the Study:

  • To investigate cerebrovascular adjustments to postural stress.
  • To understand the role of CA in preventing syncope.
  • To clarify the relationship between mean arterial pressure (MAP) and cerebral blood velocity (V(mean)).

Main Methods:

  • Continuous monitoring of CBF using transcranial Doppler (measuring V(mean)).
  • Near-infrared spectroscopy to assess regional cerebral tissue oxygenation (cO(2)Hb).

Related Experiment Videos

  • Analysis of CA as a frequency-dependent phenomenon.

    • Main Results:

    • MAP changes do not always reflect cerebrovascular events during (pre)syncope.
    • CA attenuates MAP oscillations at low frequencies, indicating it doesn't respond to rapid MAP changes.
    • A transient fall in V(mean) occurs upon standing, causing lightheadedness in healthy individuals.

    Conclusions:

    • Cerebral perfusion relies on arterial inflow pressure and adequate cardiac output.
    • Dynamic CA in recurrent vasovagal syncope patients is similar to healthy controls.
    • Understanding CA's frequency-dependent nature is key to managing syncope.