Neurogenic Shock Flashcards
This type of shock leads to the inability of the sympathetic nervous system to stimulate nerve impulses, which causes hemodynamic problems
Neurogenic shock
This type of shock leads to the inability of the sympathetic nervous system to ___________________-, which causes hemodynamic problems. This leads to a decrease in_________________ where the cells that make up our organs and tissue don’t receive enough oxygen. Hence, signs and symptoms of shock occur.
stimulate nerve impulses; tissue perfusion
NEUROGENIC SHOCK
What kind of shock is neurogenic shock ?
Neurogenic shock is a type of distributive shock (anaphylactic and septic shock are the other types of distributive shock).
This means that the vessels that deliver blood flow to the cells have an issue with distributing that blood flow.
What can cause neurogenic shock?
Spinal cord injuries that are located at the cervical or upper thoracic locations (above T6)
Drugs that affect the autonomic and sympathetic nervous system
Spinal anesthesia
Neurogenic shock is sometimes referred to as _____________- shock.
vasogenic
The ________________nervous system controls the functions we cannot consciously control like our heart rate, digestion, rate of breathing, pupil response, etc. It is divided into two systems called the:
autonomic
Sympathetic Nervous System (SNS) and Parasympathetic Nervous System (PSNS)
The ________________—-nervous system is known as the “rest and digest” system. It helps us relax by decreasing our heart rate and allows us to digest food, among other functions.
parasympathetic
The _______________— nervous system is the “keep you alive or fight or flight” system! It increases the heart rate, blood pressure, dilates your pupils for better vision etc. Therefore, a HUGE role it plays is that it controls __________________. What does that mean ?.
sympathetic; 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.
Now, it’s very important to note that the PSNS and SNS are always __________________each other out to keep things regulate in our body. For example, if the SNS had to kick in to save your life, eventually it would have to slow down and this is where the PSNS system would help. Therefore, if one system is not working (as the case with neurogenic shock…the SNS is malfunctioning), the other system will be_________________- and in a sense take over, which is why many patients with neurogenic shock will have ________________–
balancing; UNOPPOSED; bradycardia.
How does the sympathetic nervous system regulate the diameter of our vessels?
The nerve fibers of the sympathetic nervous system branch out and hang out on the layers of the vessels.
When nerve signals are fired, it will cause the neurotransmitters epinephrine and norepinephrine to be released. These neurotransmitters will cause the vessel to constrict (narrow).
However, if there is a low level of nerve firing or NO firing, these neurotransmitters are NOT released, so the vessel just relaxes….hence dilates.
This is the problem with neurogenic shock. The nerves are not being stimulated, so they are relaxed. This causes major problems!
Dilated vessels affect the ______________–. When vasomotor tone is lost, __________________n occurs and this lowers systemic vascular resistance (SVR), which causes a major decrease in blood pressure (hypotension). Due to the decreased SVR and low blood pressure,_______________– will occur in the vessels. This will _______________—the amount of blood draining back to the heart (remember there is not 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 at all! This will cause a ________in tissue perfusion.
In addition, this blood pooling will lead to a risk of ________________________) development and ______________the body core temperature (hypothermia).
blood pressure; vessel dilation; blood pooling; DECREASE; DECREASE; deep vein thrombosis (DVT); lower
Why hypothermia in neurogenic shock ?
The blood is just sitting in the extremities cooling down and not returning to the core body to be warmed. These patients will have warm/dry extremities but a cold body.
hypothermia can occur due to the body’s inability to regulate the body temperature because of hypothalamus dysfunction. This is further complicated by the peripheral vasodilation and pooling of blood in the extremities . This will lead to heat loss because the blood isn’t returning back to the body to keep it warm. So, extremities will be warm and dry, but the body will be cold (poikilothermic: loses the ability to regular core body temperature).
In neurogenic shock, Why does the venous blood pooling lead to a decrease in tissue perfusion?
There is venous pooling of blood and not much blood will be flowing back to the heart because there isn’t any resistance making it go back. This will decrease cardiac preload (the amount the ventricle stretch at the end of diastole/filling phase) and cardiac afterload (resistance the ventricles must overcome to pump blood out of the heart and this is due to the decrease in SVR).
Remember we discussed in our lecture on cardiac output that cardiac preload and afterload play a huge role with cardiac output because they affect stroke volume (the amount of blood the ventricle pumps with each BEAT), which affects cardiac output. CO is calculated by:
CO = Heart Rate (HR) x Stroke Volume (SV)
Cardiac output is the amount of blood the heart pumps per minute. When CO falls, so does the amount of blood that is rich in oxygen that flows to the cells that make up our tissues and organs. If cells don’t receive enough oxygen they start to die, and the patient starts to experience the classic signs and symptoms of shock.
If we lose the function of the SNS, the PSNS will be unopposed and _________________—-will occur.
bradycardia
The major signs and symptoms you will see with neurogenic shock are…
hypotension, bradycardia, hypothermia, warm/dry extremities but cold body
