Shock!

[kris02]

Hi there,
I was wondering if anyone had any decent flow charts/information on the basic pathophys of shock?

I am also struggling with the ANS so i think that may be my problem with understanding shock completely

I am trying to learn it for my final exam and cant seem to get my head around it.


Any help would be much appreciated

Thanks
Kris

 

[Guardian]

Nobody else is answering your question so I might as well take a stab at it. I wish your questions were a little more specific. It would also be nice to know whether this is a ALS or BLS question.

Nervous system is composed of CNS which is brain and spinal cord and PNS which is everything else.

The Autonomic Nervous System (ANS) is a component of the PNS and is the system of regulation. The ANS has 2 parts, the parasympathetic system and the sympathetic system.

Parasympathetic System (cholinergic system) is controlled through vagus nerve and its primary mediator is acetylcholine. This system slows down everything except the GI tract (increases peristalsis). It slows heart rate, respiration rate, and decreases BP.

Sympathetic system (adrenergic system) does the opposite and increases everything except peristalsis (thats why upset people have upset stomachs). Another words, it increases HR, RR, and BP. Its primary mediator is Norepinephrine, epinephrine. This system is stimulated through the Alpha and Beta receptors. Alpha receptors cause bronchoconstriction and vasoconstriction. Beta receptors cause increase HR, bronchodilation and vasodilation. Ex. epinephrine stimulates both alpha and beta receptors and that's why it does what it does.

Shock is widespread inadequate tissue perfusion. It is caused by low blood volume, mechanical heart problems (the hearts not pumping good enough because of tension pneumothroax, myocardial contusion, etc.), or relative hypovolemia (neurogenic shock) where nervous system relaxes muscle tension on veins and suddenly there is not enough blood to maintain adequate BP.

When someone goes into shock, the ANS jumps into action when the sympathetic system releases epi which as we now know increases vasoconstriction, increases HR, shunts blood to vital organs (brain and heart) and hopefully increases BP.

This is only the beginning. There have been books written on shock. Hopefully this will give you a basic understanding.

 

[Guardian]

I'm bored so I'm going to add a few more tidbits about shock that all ALS providers should know.

The battle against shock is won or lost at the cellular level. During shock, the capillaries can selectively supply undernourished tissue with blood and temporarily bypass tissue with no immediate need. They accomplish this because the pre-capillary sphincter responds to local tissue demand such as acidosis and opens as more arterial blood is needed.

All shock pts. die of hypoxia. We can replace blood volume with normal saline but we can't replace the bloods ability to carry oxygen (at least not yet). With lack of O2, the cell dies which kills tissue which kills organs which kills people.

Cellular metabolism plays a big role. When everything is going right, aerobic metabolism is taking place and glucose is broken down into pyruvic acid. Then the Krebs cycle takes over and breaks pyruvic acid into usable energy. The Krebs cycle requires oxygen. When things are not going well (shock), anaerobic metabolism takes over. Glucose is broken down into pyruvic acid just like aerobic metabolism but then never finishes with Krebs cycle because the lack of O2. Pyruvic acid then accumulates and turns into lactic acid. Lactic acids then accumulate and the cell dies. Then lactic acid then gets into the circulatory system and wreaks havoc. This increases acidosis which decreases catecholamine response.

 

[kris02]

Thanks

Hi guys i know it is quite a boring topic so i appreciate your help. Thanks


Kris!