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What is shock?

Created by Ian Mannarino.

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Video transcript

- [Voiceover] I'm sure most of us have seen those medical shows or those medical movies where a patient is hauled into the operating room or is in the emergency department, and the physician is furiously working on them, while somebody on the medical team is screaming, "Doctor, the patient is in shock!" Everybody continues to furiously work on the patient. There's a lot of commotion. It makes sense, because this is a life-threatening problem. Shock. But what is shock? To understand, let's go ahead and tackle some of the basics. So we know in the body there is something called the cardiovascular system, which is essentially your heart and blood vessels. So, here's a blood vessel. Blood passes through blood vessels. The reason we have blood is to distribute nutrients and energy and oxygen to the different cells of the body. So here we have some cells. So this is the normal physiological process by which we deliver oxygen to the tissues. But what if we're not able to deliver as much oxygen, which I'm doing with these little white dots here? What if we can't deliver as much oxygen to the tissues as we need? What if the O2, the oxygen that is delivered, is inadequate? What if it's less than the oxygen that is required by these cells? This is essentially what happens in shock. Shock is inadequate delivery of oxygen to the tissues. It's also known as tissue perfusion. So what is tissue perfusion? Tissue perfusion is basically the amount, so the volume of blood, that can be distributed over a certain amount of time, over, or to, a certain amount of tissue. Amount of tissue. So volume over time is essentially blood flow. So this is flow of blood to a certain amount of tissue. This could be in grams of tissue. So this might be written as something like 20 milliliters per minute delivered to 100 grams of tissue. So profusion is just a measurement of how much blood can reach a certain amount of tissue in a given time period. Now we know that cells require oxygen, and know there are things that can increase or decrease the amount of oxygen required by cells, So, for example, if you're exercising, you're going to have an increased need for oxygen. Increased oxygen requirement. But when we talk about shock, we mostly focus on this oxygen delivery. So let's take a look at oxygen delivery through the cardiovascular system. So here we have our heart. I'm going to do a good old Valentine's Day heart. The heart is really divided into four chambers. The right side of the heart. This is the patient's right. So you're looking at a patient. This is the right side of their body. And the left side of the heart. We've got the atria, which is where blood first enters into either the right or the left side of the heart, and we have the ventricles. So this will be the right ventricle, and the left ventricle, which will essentially pump blood to where it needs to go. So let's follow to the left side of the heart. So we can follow blood flow from the left side of the heart as it goes and gets pumped to the system, where different organs of the body, so these are cells from different organs of the body, receive oxygen, nutrients, glucose, everything they need from the blood. Then blood, after being deoxygenated, returns to the right side of the heart. Then this blood, this deoxygenated blood, is pumped again from the right side of the heart, to the lungs. Now obviously this isn't anatomically correct because the lungs are on the right and left side of the heart. They surround the heart on both sides. They're kind of situated on both sides of the heart. But this will really suffice for the purposes of our diagram. And so, blood will be oxygenated and returned to the left side of the heart to be pumped again, pumped to the organs of the body. And so this is the cardiovascular system. So when you think about shock, I want you to think about how the cardiovascular system is affected so that you can figure out the different types of shock. Because there are four different types of shock. First of all, remember our definition of shock is decreased tissue perfusion. So one thing that we could imagine is, if we decreased the volume of blood, that would decrease perfusion. Right? Because perfusion is volume over a certain amount of time delivered to a certain amount of tissues. So low blood volume is known as hypovolemic shock. Hypo means low. Volemic means volume. And so you could imagine if a patient is vomiting or is having diarrhea, sorry for the visual. Or maybe they're bleeding. This all leads to volume loss from the patient. If it's severe, it can lead to hypovolemic shock. So what's something else that can decrease tissue perfusion? What if we decrease the flow through the entire system? Well what causes the cardiovascular system to function? It's the heart. So if the heart can't contract and push blood forward, that can lead to shock. And so that's known as cardiogenic shock from the heart. Now what else can prevent blood flow? Well what if there's an obstruction in the cardiovascular system? That's another type of shock. Obstructive shock. There are many examples of obstructive shock. One example is a pulmonary embolism. A clot in the pulmonary arteries. If this is severe enough, it can prevent blood from flowing through, which is decreased blood flow, decreased tissue perfusion. So that's another type of shock. Finally, the fourth classification of shock is known as distributive. Distributive shock includes different shocks such as septic shock, anaphylactic shock, neurogenic shock. What happens in distributive shock is fluid ends up collecting in between the cells of organs that are requiring the oxygen, and the blood vessels that are delivering that oxygen. If a lot of fluid accumulates, it's harder for oxygen to get to the tissues. It has to pass through a lot of fluid to reach the tissues. By tissues I mean the organs, like kidneys, the liver, or maybe the gastrointestinal organs. So finishing up, I want you to ask yourself, what happens to the gastrointestinal system, the intestines, when they don't receive enough blood? Well, if it's mild, if they're not receiving enough oxygen and blood. It might be something mild like nausea. If it's severe enough if left unchecked for a long time, the cells of the intestines, they die. This will lead to bowel perforation, or intestinal perforation.