Shock, Sepsis, Sirs, Mods Flashcards
What a shock?
Not enough oxygen for tissue perfusion.
That is really the essence of shock one so when you watch TV and you watched all of the medical dramas, and the patients are in shock, what are they treating them with?
Fluids. which is the exact second thing to do. The first thing to do is oxygen. Always remember that.
So there is a few things that I want to review, tissue and oxygen perfusion is directly related to mean arterial pressure, and there are three factors that influence mean arterial pressure.
The first factor is total employment volume. Second factor is cardiac output, and the third factor is the size of the vascular bed.
So if total blood volume and cardiac output are low, mean arterial pressure will be low.
If cardiac output and total blood volume are high, the mean arterial pressure will be high.
What is the required for minimum mean arterial pressure to perfuse the heart?
- So any time that the mean arterial pressure drops below 60, we should start to get nervous.
if your heart rate is higher than your systolic pressure…
you need to be calling somebody.
Now, in terms of the size of the vascular bed, if it becomes larger, the mean arterial pressure drops.
So when I say that the vascular bed becomes larger, what am I really saying? Vasodilation. Exactly.
So if we had vasoconstriction, and all of a sudden the vascular bed is smaller,…
the mean arterial pressure goes up. We get faster flow.
What controls vascular bed size ?
sympathetic Stimulation. So if you have an increased sympathetic nervous system stimulation, you are going to increase mean arterial pressure.
Any issue that impairs oxygen delivery to tissues and organs can start the syndrome of shock.
Any issue that impairs oxygen delivery to tissues and organs can start the syndrome of shock.
Shock is a syndrome because
it occurs in a predictable sequence and pattern.
Additionally shock is a metabolic condition, because
oxygen delivery is not adequate to meet tissue demand. It represents a whole body response. Everybody’s system is affected by shock.
now there are some common cellular changes that occur in all of the types of shock. The first one is…..
decreased energy production. So decreased ATP
With that decreased energy production comes decreased aerobic metabolism, and increased in aerobic metabolism. What is the outcome of increased anaerobic metabolism?
Lactic acid. Which results in what type of acidosis? Metabolic.
You have decreased cell function, so whatever the cell is supposed to do, it’s not working right.
So if it is a pancreatic cell, you have insulin issues. If it is a heart cell, you have rhythm issues. If it is a lung cell, you may have diffusion issues. So it could be an issue with oxygenation, or what is the other part? Ventilation.
You will have altered integrity of the cell membrane. If the cell membrane alters itself, what happens inside the cell?
It is going to be “Bad”. The cell is going to explode. We call this process apoptosis. because it is what the cell is doing. It is popping open. With those changes in the cellular environment, you will have an acidosis, electrolyte changes, rupture of the lysosome and then apoptosis.
hypovolemic shock. What is really going on here?
too little circulating blood volume.What is important here is that in this extracellular fluid, a quarter of this is plasma, and three quarters of this is interstitial.
in hypovolemic shock when there is too little circulating blood volume are issue is decreased intravascular volume.. Because of that decreased intravascular volume, we had decreased venous return. What does that sound like?
CHF.
decreased intravascular volume leads to…
decreased venous return…
decreased venous return leads to….
decreased ventricular filling…
decreased ventricular filling…leads to…
results in a decreased stroke volume….
results in a decreased stroke volume leads to….
a decreased cardiac output..
a decreased cardiac output leads to…
decreased tissue perfusion, which takes us to cellular changes….
those cellular changes are those that I just mentioned where you have decreased ATP production,
where you have decreased cell function, where you have changes in the cellular environment, and then the cell gets mad and it blows itself up. Suicidal cells.