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I am studying nursing and have a question regarding the physiological response to shock (decreased perfusion). In lecture notes supplied by the lecturer, he indicates that there is a neural, hormonal and immune response to shock that is compensatory.

The neural component is the activation of the sympathetic nervous system, and hormonal response is through RAAS, etc. This makes sense, as these mechanisms attempt to increase blood pressure and blood volume

I don't understand the immune response, though, which is described as the release of pro-inflammatory mediators, which lead to endothelial cell damage, making the vessels leaky, leading to oedema. So how is the compensatory, it seems disruptive? And why exactly would pro-inflammatory mediators be released in response to shock in the first place?

esotechnica
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  • While I'll try to flesh out an answer when I can, try to access this article. There are some fair points, but importantly that tissues release inflammatory mediators in response to damage and stress. – CKM Nov 08 '17 at 01:24
  • Also this article: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4846925/ – CKM Nov 08 '17 at 01:45
  • Great articles, thanks. I think this basically fills the gap in my knowledge. So ischaemia from any form of shock causes endothelial damage, which leads to inflammation, etc... – esotechnica Nov 08 '17 at 12:05

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First: what is inflammation. From wikipedia https://en.wikipedia.org/wiki/Inflammation

Acute inflammation is the initial response of the body to harmful stimuli and is achieved by the increased movement of plasma and leukocytes (especially granulocytes) from the blood into the injured tissues. A series of biochemical events propagates and matures the inflammatory response, involving the local vascular system, the immune system, and various cells within the injured tissue.

Second re shock: why does it happen? If I go into shock from blood loss after a terrible knife juggling accident I will probably not have the inflammatory piece: I am dying from lack of blood and consequent low blood pressure.

What if I am in septic shock? That means shock caused by organisms, usually bacteria, in the blood stream. Bacteria are the ancient enemy and we have layers upon layer of defense accumulated over evolutionary time. The reason we have them is that somehow, our ancestors that had them had some fitness advantage - probably because they survived having bacteria in the blood.

Some of the stuff that comes with that package does not seem very adaptive - like the leaky vessels and lungs filling up with fluid. Maybe we see the wild extreme of this reaction but to a lesser degree (lesser infections?) those inflammatory responses are good? Maybe releasing a storm of neutrophils has unavoidable side effects for the surroundings - like the Avengers fighting an alien army in NYC? It was tough on NYC. Maybe those extreme shock reactions save the organism 1 time in 10, which is better than the odds otherwise with an overwhelming bacterial infection.

Bottom line though is that bacteria in the blood in great numbers is an existential threat to the organism. Desperate times call for desperate measures.

Willk
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