Obstructive shock

- Obstructive shock is very similar to cardiogenic shock. And that's actually why I have this heart drawn out right here. In cardiogenic shock, the problem is the heart is not able to squeeze properly and pump blood forward. In obstructive shock, it's actually very similar except the issue here is it's an obstruction. There's an obstruction either surrounding the heart or in the blood vessels that prevents blood from being pumped forward. But, because it's very similar, you can actually have very similar symptoms as you see in cardiogenic shock. For example, an obstruction can cause blood to back up into the lungs and into the right side of the heart. And of course blood in the lungs can cause coughing and difficulty breathing due to all this accumulation of fluid in the lungs. It's known as pulmonary edema. As blood continues to back up as we were showing, this fluid overload can cause an enlarged heart. Cardiomegaly. Fluid continues to back up into the system, you might see something called JVD, jugular venous distention, as blood backs up into the neck. And if it's severe enough, blood can back up and cause global swelling throughout the body. This total swelling throughout the body is known as anasarca. So, pulmonary edema, cardiomegaly, jugular venous distention, and anasarca, total body swelling, can all result from obstructive as well as cardiogenic shock. It's all signs of just fluid overload. Add in such signs as increased heartrate, tachycardia, and decreased blood pressure from the inability of blood to be pushed out of the heart, this hypotension and, of course, decreased oxygen delivery to the system. So, what can cause obstructive shock? Well, for that let's go ahead and take a look down here. And here I've got four different hearts drawn out so that we can go over different types of obstruction. And the first type I want to go over is called cardiac tampenade. Cardiac tampenade is pressure created around the heart because of accumulation of fluid or blood in the pericardial sac. Now, what the heck's the pericardial sac? Well, it's actually a sac that the heart sits in that is lined with cells that produce a fluid that helps keep the heart frictionless as it beats. Because your heart's going to be beating your whole life, so putting it in this pericardial sac with an oil-like fluid allows for this decreased friction. Now, this issue with pericardial tampenade is an over-accumulation of fluid. And this is known as a pericardial effusion. And this effusion might occur, for example, let's say there's a tear in the ventricular wall of the heart. Blood's going to start pouring out. And as it starts pouring out, it just fills up the pericardial sac. And as the fluid continues to accumulate, it puts pressure on the heart. Because there's this fluid surrounding the heart, the heart can no longer expand. And so what you see is this area, these compartments of the heart, end up becoming smaller. Because the heart is just so constricted. So, when the heart does squeeze, it can't push that much blood out because there's not enough blood that can get into the heart. And also because of this increased pressure surrounding the heart, if blood is trying to get back from the venous system into the inferior vena cava or the superior vena cava, trying to get back into the right atrium, not only is the compartment smaller but because there's such a high pressure around the heart, the blood can't even get in there. Remember that fluids and gasses tend to go towards lower pressure. I mean, that's exactly how the heart functions. When it squeezes, pressure increases in the heart to push blood out. But now the trouble is there's too much pressure around the heart, so blood can never even get in through the blood vessels into the heart. So, you have decreased venous return into the heart, along with decreased compartment size. So, the ventricles and the atria are decreased in size, which decreases the amount of blood that can be pushed out of the heart, the stroke volume. Now, cardiac tampenade, the fluid accumulation around the heart is just one example that involves this pericardial sac. Another example is constrictive pericarditis. Constrictive pericarditis is when the pericardium gets very rigid. So, rather than blood accumulating around the heart, the pericardium is putting pressure directly on the heart. So, the pericardium might become constricted because of infection, a lot of scarring occurs, something like that. But you get the same concept. Blood cannot be pushed out of the heart. Another example of the obstructive shock is a tension pneumothorax. What's a tension pneumothorax? Tension pneumothorax is when you have air that leaks into the pleural cavity. Now, what's the pleural cavity? The pleural cavity is a space that includes your lungs and the heart. And this space is bordered by the diaphragm, the chest walls, which I've drawn on the lateral sides, and soft tissue and other things on the top side. Now, this is really an oversimplification of the pleural space. But, I just want to give you an idea that it's really an enclosed space. Now, the concept here is you again have an increase of pressure. But this time it's not just surrounding the heart. It occurs in the pleural space as well. So, for example, let's imagine a patient has a stab wound. Let's say he got into a fight with somebody with a knife and they stabbed him. Now, let's say the chest wall acts as a one-way valve. And air is able to get into the pleural space, but it cannot escape. With each deep breath that the patient takes, not only are they drawing air into their lungs through their trachea. But, also, air's getting pulled into the space around their lungs. This causes all of the organs to shift over, away from this air in the pleural cavity, also known as the thoracic cavity. So, this is a pneumothorax, air in the thoracic cavity. And it's causing all of this tension as it pushes all of the organs to the side, including the lungs, the heart, and the trachea. So, this causes constriction on the heart. And, just like we saw before over here, blood can't get into the heart, because there's a higher pressure. And so, blood is not able to really break this pressure barrier. So, similarly to tampenade and constrictive pericarditis, you have decreased venous return and constriction of the heart. Next, is a pulmonary embolism. Now, let's say a patient falls and breaks their leg. And, their leg is put in a cast to immobilize it. So, this immobilization may actually cause blood to clot, because it doesn't move as well back to the heart. So, blood in one of the deep veins of the leg may clot. So, that's a deep vein clot, also known as a deep vein thrombosis, which we also like to call a DVT, deep vein thrombosis, in the medical community. So, this DVT may potentially break off. And, when a clot breaks off it's known as an embolism. So, it embolizes. And, you can see that it can fit in the heart, but it gets stuck in the lungs, in the pulmonary arteries. And, if it's a big enough clot, it can be so severe that when the heart tries to pump, blood from the right side of the heart can't really make it to the left lung. So, blood can only go to the right lung in this case. So, only one pulmonary vein is returning blood to the heart. So, only so much blood can be squeezed back out to the brain, as well as to the organs and other parts of the body. The final obstruction that I'll talk about is stenosis, aortic stenosis. Aortic stenosis is narrowing, stenosis means narrowing. So, this is narrowing of the aortic valve. So, here's the aortic valve. And it actually has three leaflets. And your entire life these leaflets are going to open and close, allowing blood to be processed through the heart. Now, as a patient ages, calcium that's in the blood may start to get stuck on these valves. This little yellowish-orange is calcium depositing on the valves. This causes the valves not to be able to open and close quite so smoothly. And, in fact, deposition can get so bad that it really narrows the valve. So, you can see even when the valve tries to open, there's only really a small area that blood can pass through. So, if it's severe enough, it can cause obstructive shock. So, what sort of labs would you want to get for a patient who has obstructive shock. First of all, you want to get your typical lab values, such as a serum lactate. Or, an ABG, arterial blood gas. So, this allows you to, so these are your typical values that you'll get in any sort of shock. But, you'll also maybe want to get other laboratory and diagnostic tests that can help you diagnose an obstructive shock. So, I won't go into too much detail, but the idea here is you want to use tests that will help you diagnose these specific conditions. So, for example, cardiac tampenade and constrictive pericarditis, you might want to use an ultrasound of the heart, an echocardiogram. In the case of tampenade, for example, it can show you that there's blood or fluid accumulation around the heart. For something like a tension pneumothorax, maybe getting an x-ray will help you diagnose this disease. Or, better yet, there's a clinical way to diagnose. So, I want you to go ahead and feel your throat. Now, when you feel you can tell it's in the middle for you. However, in a patient who has a tension pneumothorax, it might be deviated towards one side or the other. So, for example, if a patient has a right tension pneumothorax, as we see here, the trachea is going to be pushed along with all the other organs and be deviated to the left side of the patient. So, a clinical observation like that can help you save a patient's life, because you can immediately diagnose and treat the patient. So, what should we do to treat obstructive shock? The major way to treat obstructive shock is to relieve the obstruction. Relieving the obstruction can actually stop the shock altogether very quickly. So, for example, in a tension pneumothorax, once diagnosed, you can treat immediately with needle throracostomy. What needle thoracostomy is is insertion of a hollow tube into the chest wall. And that allows all this air that has accumulated to escape out and relieves the tension in the thoracic cavity. If aortic stenosis is the problem, maybe a new valve, known as a valvuloplasty, is required. Pulmonary embolism, dissolving this embolis or removing it directly by guiding a catheter into the heart and grabbing hold of this embolism. And, for something like tampenade, you can stick a needle into this pericardial cavity and draw out the fluid. So, treatment of obstructive shock, relieve the obstruction.