Neurogenic Shock Flashcards
- This type of shock leads to the inability of the SNS to stimulate nerve impulses, which causes hemodynamic problems
- This leads to a decr in tissue perfusion where the cells that make up our organs & tissues don’t receive enough oxygen; hence, s/s of shock occur
- Is a type of distributive shock (like anaphylactic & septic), meaning that the vessels that deliver blood flow to the cells have an issue w/distributing that blood flow
- Here, it’s d/t massive vasodilation b/c the SNS has lost the ability to stimulate nerves that control vessel vasomotor tone (this is the ability to regulate the diameter of the vessels)
What can cause neurogenic shock?
- SCI’s located @ the cervical or upper thoracic locations (above T6)
- Rx’s that affect ANS & SNS
- Spinal anesthesia
Neurogenic shock is sometimes referred to as vasogenic shock
Pathophysiology of Neurogenic Shock/Pre-Briefing
- ANS controls the functions we cannot consciously control like our HR, digestion, rate of breathing, pupil response, etc
- Divided into SNS & PSNS
PSNS
- Known as the “rest & digest” system
- Helps us relax by decr our HR & allows us to digest food, among other functions
SNS
- “keep you alive or fight or flight” system
- Incr HR, BP, dilates pupils for better vision, etc
- Therefore, a HUGE role it plays is that it controls VASOMOTOR TONE > this means that the SNS regulates the diameter of our vessels
- It will cause our vessels to constrict or dilate as needed, depending on the signals it receives from the body
☆ PSNS & SNS are always balancing each other out to keep things regulated in our body
! If 1 system is not working (such as w/neurogenic shock… SNS is malfunctioning), the other system will be UNOPPOSED & in a sense take over, which is why many pts w/neurogenic shock have bradycardia
How does the SNS regulate the diameter of our vessels?
- The nerve fibers of the SNS branch out & hang out on the layers of the vessels
- When nerve signals are fired, it will cause the neurotransmitters epi & norepi to be released
- They will cause the vessel to constrict (narrow)
- H/e, if there’s a low lvl of nerve firing or NO firing, these neurotransmitters are NOT released, so the vessel just relaxes, or dilates
! This is the problem w/neurogenic shock → the nerves are not being stimulated, so they’re relaxed (! causes major problems)
Why?
- Dilated vessels affect the BP
- When vasomotor tone is lost, vessel dilation occurs & this lowers SVR, which causes a major decr in BP (hypotension)
- D/t the decr SVR & low BP, blood pooling will occur in the vessels
- This will DECREASE the amt of blood draining back to the heart (remember, there’s no pressure/resistance helping to push it back so it just hangs out away from the heart)
What does this leave the heart to pump?
Hardly anything @ all!
This will cause a DECREASE in tissue perfusion
In addition, this blood pooling will lead to a risk of DVT development & lower the body core temp (hypothermia)
Why hypothermia?
The blood is just sitting in the extremities cooling down & not returning to the core body to be warmed
These pts will have warm/dry extremities but a cold body
Why does this lead to a decr in tissue perfusion?
There’s venous pooling of blood & not much blood will be flowing back to the heart b/c there isn’t any resistance making it go back
This will decr preload (the amt the ventricle stretches @ the end of diastole/filling phase) & afterload (resistance the ventricles must overcome to pump blood out of the heart & is d/t the decr in SVR)
- When CO falls, so does the amt of blood that’s rich in O2 that flows to the cells that make up our tissues & organs
> If cells don’t receive enough O2, they start to die, & the pt starts to experience the classic s/s of shock
Also, hypothermia can occur d/t the body’s inability to regulate the body temp b/c of ____ dysfunction
This is further complicated by the peripheral vasodilation & pooling of blood in the extremities
hypothalamus
This will lead to heat loss b/c the blood isn’t returning back to the body to keep it warm (! extremities warm & dry BUT body cold) [poikilothermic - loses ability to regulate core body temp]
____ will occur too
HR is controlled by both the SNS & PSNS
Bradycardia
____ incr the HR & ____ works to decr the HR
SNS, PSNS
