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In Acupuncture, Trigger Points and Musculoskeletal Pain (3rd Edition), Baldry advances the following:

"When the Myofascial Trigger Point nociceptor-sensitizing substances bradykinin and prostaglandins are released into the tissues as a result of trauma-induced inflammation, they give rise to the development of both vasodilatation and increased vascular permeability.The effect of this is to cause oedema to develop with compression of veins and resultant tissue ischaemia. As a consequence of this a vicious circle is liable to be created because the ischaemia then leads to the release of still more MTrP nociceptor sensitizing chemical substances."

Why does vasodilation and increased vascular permeability entail oedema and vein compression?

Shouldn't vasodilation counterbalance vein compression and, thus, hinder ischaemia?

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Increased vascular permeability means fluid leaks more readily from blood vessels. That leakage builds up in the surrounding tissue, which causes edema. The edema squeezes veins, thereby compressing them, which means they can't do their job of draining the tissue efficiently, and that can lead to the vicious circle he mentions.

Vasodilation means the vessels increase their inside diameter, but it doesn't prevent them from being compressed, so no, nothing is counterbalanced.

  • Why does pressure from oedema squeeze veins instead of forcing leakage back into blood vessels? – Bruno Schiavo Feb 2 '17 at 13:20
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    @BrunoSchiavo For that to happen the fluid in the tissue would have to be under greater pressure than your diastolic BP. I think that much pressure would cause you to be blown up like a balloon. And I don't know if this is true but it's possible fluids can't pass as easily into vessels as out. – Carey Gregory Feb 2 '17 at 15:13

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