Understanding Obstructive Shock Causes

All right, welcome to the fifth lesson in our series of lessons on shock. In this lesson, we're going to be talking about obstructive shock. And my name is Eddie Watson, and I will be presenting this series of lessons. And before we begin, in order to make sure that you stay up to date on our lessons as we release them, make sure and subscribe to our channel below. Don't forget to hit that bell icon in order to be notified when the new lessons become available. In our last lesson, we extensively covered cardiogenic shock and what exactly is going on in pump failure. In that lesson, I did mention that there are other causes of what are oftentimes categorized as cardiogenic shock, but oftentimes we can pull out some of those causes into a subcategory that we call obstructive shock. And essentially, obstructive shock is just that. It's an obstruction that impacts the flow of blood due to one of various mechanical issues that are going on. One important thing to note is that while the pathophysiology behind the mechanical causes are certainly different, the end result is ultimately the same thing and is very similar to what you would see in cardiogenic shock, which is that pump failure. So in this lesson, it's going to be a little bit different in the sense that we're going to talk through each of these causes and at that time go through the pathophysiology of what's happening, talk about the signs and symptoms. diagnosis and treatment before moving on to the next one. And so with that said, let's go and move on to our first cause of obstructive shock, which is going to be tension pneumothorax. And as always, I've got a drawing to help guide us through this. So let's talk a little bit about tension pneumothorax and what exactly is happening. So here we have our lungs. And typically we have our chest wall that runs along here. And typically we have the intrathoracic space here, which goes between our lungs and our chest wall. And this is normally an airtight seal. And this is really what helps to keep the lungs inflated. And so normally in this space here, the pressure that's in there is less than the pressure that's inside of the lung. And that's what allows the lung to expand. But what can happen sometimes is that cavity gets opened up and exposed to the outside air. And that air begins to come in and fill in this space. And eventually that decrease in pressure begins to go away. And what happens is that air will begin to fill in that space and change the pressure difference. And with each successive breath, the lung will get smaller and smaller, and that pressure will continue to get greater and greater on the outside of the lung. And ultimately, if either severe enough or left to go on long enough, the lung can completely collapse. And part of the issue is that this air has no way to escape back out. And so as the air continues to build and build, it continues to put more and more pressure inside the cavity and ultimately can lead to the collapse of the lung. and even more severe issues related to shock. There can be multiple causes of this, but some of the most common are going to be some sort of traumatic penetrating injury, and even positive pressure ventilation can cause an injury that allows air to escape into this cavity and ultimately leading to tension pneumothorax. And really what's going on in this process is as that pressure builds up, we begin to see pressure exerted this way. And there's a few different things that are going to happen as a result of that. Part of it is we're going to be putting pressure on the vena cava, and that's ultimately going to cause that to narrow down and lead to a decrease in the return of blood to the right atrium. And this ultimately will decrease our preload and our cardiac output. In addition to that, the pressure is also going to be pushing and putting pressure on the heart itself. which is going to constrict that heart, which ultimately can prevent the filling, as well as the contraction of the heart, again, leading to a decrease in cardiac output and ultimately our shock state. And depending on the cause and the severity, this can either happen very slowly over time, or sometimes this can come on quite quick and sudden. And so some of the signs that you'll see in a patient tension pneumothorax probably the first and most notable sign is going to be a deviated trachea and what happens is again due to that pressure that trachea is going to deviate away from the side that the tension is developing on you also can see a hyper expanded chest on the side of the tension and on that side you're going to have an increase in a percussion sound as well as either decreased or in the case of a completely collapsed lung absent breath sounds. You're also going to see very little movement of the chest wall with respiration on that side. Along with this, you're going to see increased respirations and tachypnea as well as hypoxia. And in addition to this, all the classical signs that you would see with a patient in cardiogenic shock. So in order to diagnose this, there's really two main things that you're going to look for. The first is going to be that tracheal deviation and it's important to note that this is away from the side that the tension is developing on and the second is going to be a chest x-ray and in the case of attention pneumothorax it's going to be very obvious because you're going to have nothing but black black space where the lung should be on the side that's affected now in terms of treatment when we talk about treatment one of the very interesting things about most of the cases of these various causes of obstructive shock, that if you relieve the obstruction oftentimes, and oftentimes very quickly, the shock can be completely stopped. And so when we talk about the treatment for the tension pneumothorax, again, there's primarily two things that we look for. One, and this is more often in a field environment, but you have needle decompression. And this essentially inserts a needle into that thoracic cavity, allowing the air to escape and relieving that pressure. And more commonly within the hospital setting, you're going to have a chest tube insertion. But one really important takeaway with this is sometimes this can progress very quickly and have very severe consequences. That this can be a very life-threatening situation, which can cause your patient to go into full-on shock. rapidly progress to PEA and possibly even death. So now moving on to the next cause of obstructive shock, we're going to talk about cardiac tamponade. And so like with everything else, let's go and do a quick primer as far as what's happening. So what's happening here is normally we have our pericardial sac, and that goes around the heart and typically we have just a little bit of fluid in there for lubricating and allowing the heart to move freely. But what can happen sometimes is we begin to get a buildup of, and this fluid can come in many forms, you know, it can be just plasma volume. In some severe cases, you can have buildup of pus from infection, but probably one of the more common ones is going to be a buildup in the accumulation of blood. And so again, what happens is as that fluid collection builds and grows, that the heart loses its ability to expand. And so this ultimately leads to a decrease in the chamber size, which ultimately means less blood is ejected each time the heart beats. In addition to that, the pressure that's exerted on the heart is going to prevent the flow of blood into the chamber, decreasing that venous return to the heart, again impacting our cardiac output. And when it comes to talking about cardiac tamponade, it really does not take that much fluid in order to start seeing some severe consequences and ultimately a shock state. And so when we have our patient who is experiencing shock as a result of cardiac tamponade, there's a couple key things that we would be looking for. Again, in addition to all the typical cardiogenic shock signs that we would see, one telltale sign that we're dealing with cardiac tamponade is we're going to be looking for what we call Beck's triad. And essentially this is three things, muffled heart sounds, jugular venous distension or JVD, and hypotension. And even more specific in this hypotension, what you're going to see is a narrowing of the pulse pressure and the pulse pressure is essentially the difference between your systolic and your diastolic. So in order to diagnose cardiac tamponade, really the true gold standard is going to be with an echo or ultrasound of the heart. And really the treatment for the tamponade is going to be pretty simple. We need to drain the fluid, and this can come in several forms. If your patient has had open heart surgery, it may be an adjustment of the chest tube. This may mean a pericardial synthesis or potentially even a pericardial drain. And again, just like with other forms of obstructive shock, oftentimes relieving the obstruction will completely resolve this state of shock. Alright, so the next cause of shock that we're going to hit on very briefly is what we call constrictive pericarditis. And again, we have that pericardial sac. And what can happen here is over time, either due to infection or scarring, that this can become thickened and rigid, and this can put pressure in on the heart. And again, ultimately reducing the heart's ability to fill and beat properly, resulting in decreased cardiac output and ultimately a shock state. And just to real quickly hit here, just some of the Treatment modalities that you might see would be things such as NSAIDs for anti-inflammatory, steroids as well, and in some cases this may lead to surgery and having a pericardectomy. And that will be the extent of what we talk about with constrictive pericarditis. All right, the next one that we'll talk about here is aortic stenosis. And essentially what happens here is if we look at our aortic valve, normally we have our three leaflets. And what can happen is over time, calcium can build up here. And this calcium can prevent either the valve from opening or even closing smoothly. And so over time, if this calcium continues to build up, we can begin to severely narrow and limit the amount of blood that can go out into the aorta. This again ultimately is going to decrease our cardiac output and can lead to a shock state. And like with all the others, classic cardiogenic shock signs are what we're going to be looking for. One thing that you will often notice is that they have a positive murmur. And just as with cardiac tamponade, Our gold standard for diagnosing this is going to be with an echo. And finally, our treatment of aortic stenosis is really going to involve just a couple of things. We can do a valvuloplasty, which essentially attempts to reopen this narrowing. You can also look to get a new valve. And this can either be done with open heart surgery, or oftentimes these days we're looking at less evasive means such as a TAVR, which is essentially the placement of a new aortic valve via a catheter. And sometimes this doesn't require a new valve, but just going in via open heart surgery and doing a valve repair. But ultimately though, if we fix the underlying cause and we restore that outflow tract, then oftentimes those signs of shock can dissipate quite quickly. All right, and so the last of these causes of obstructive shock that I'm going to talk about is something that we call a pulmonary embolus. And so what happens... in the case of a pulmonary embolus is there can be a couple different things that can go on. Probably the most common form is patient developing what they call a deep vein thrombosis, and this is where a large clot that is formed and a deep vein, typically in the legs, breaks off and travels into circulation. Sometimes in the case of trauma and large bone fractures, you can end up with a similar process, but with what they call a fat embolus, and this can also break free and enter the bloodstream, just like the DVT will. And so what happens is, as these enter the bloodstream, they flow relatively freely into the right side of the heart and can enter into the pulmonary vein on their way to the lungs. And what happens here is the embolus will never make it to the left side of the heart. It's never going to pass through the capillary bed, so we don't ever have to worry about this going to the left side and potentially into arterial circulation and potentially causing a stroke. But a very severe situation can arise depending on the size of the embolus. So the first of these is if it's large enough, it can just about occlude off one of the sides of the pulmonary circulation. And this thus would severely limit the amount of blood flow that's going through here and ultimately returning back to the left side of the heart. And potentially, if this embolus is large enough, that this can lead to a shock state. But potentially even more important and even more severe is what we call a saddle PE. And that's essentially where you end up with some sort of embolus so large that it sits in the saddle of the pulmonary vein and completely stops all blood flow or the majority of the blood flow from continuing. past the right side of the heart. And as you can imagine, this is a pretty severe situation that they would find themselves in. And in fact, 25% of the people that have this saddle embolus will experience sudden death. And again, with a PE, you're going to see all those same cardiogenic shock signs, but you may also notice increased respiratory rate and pallor or cyanosis. due to the lack of oxygen delivery to the blood. Now there are a couple different tests we can use to diagnose. The first of these is going to be what we call a VQ scan, and this is looking for a VQ mismatch, or a ventilation and perfusion mismatch. But the other one, and again the more gold standard option, is going to be a CT angio. And that will give you a clear picture of if there is a PE and exactly where it is and how big it is. And finally, to talk about the treatment for a PE, you really have two options available to you. You can dissolve it. This is going to be with TPA, TNK, heparin to prevent the forming of more clot. or to remove it, so essentially to have an embolectomy. And this sometimes can be done in procedural sites such as interventional radiology or may require open heart surgery in order to go in there and remove that embolus. And again, especially in the case of a large PE, as soon as you can remove that embolus, oftentimes you can see that shock state resolve fairly quickly. Alright, so that pretty much concludes our coverage of the different causes of obstructive shock. In each case, we went through an explanation of what exactly was happening, what you would be looking for, some of the diagnostic procedures, as well as the treatment for each. Again, the key takeaway, though, is that ultimately these are leading to a state of pump failure, and so the manifestation of obstructive shock is going to look oftentimes identical to cardiogenic shock, and it is only going to be through some of the other... diagnostic tests or a few signs and symptoms in some cases that would help you distinguish that this is a form of obstructive shock. And ultimately, the biggest thing is to resolve that underlying cause and oftentimes your patient will make a very rapid recovery. All right, and so with that, I will go ahead and conclude this lesson. As always, I want to thank you for watching the lesson today and I really hope that you found this informative. If you liked the video and you did find it useful, please make sure and hit that like button below. It really helps to spread the word about our channel. And in the comments below, tell us your favorite part, or feel free to ask us any questions that you may have had about this lesson. Finally, make sure and check out our next lesson in this series, which is going to be covering distributive shock, and specifically neurogenic and anaphylactic shock. Or feel free to check out another one of our great series of lessons on hemodynamics. As always, thanks for watching and we'll see you in the next lesson.

In our last lesson, we extensively covered cardiogenic shock and what exactly is going on in pump failure. In that lesson, I did mention that there are other causes of what are oftentimes categorized as cardiogenic shock, but oftentimes we can pull out some of those causes into a subcategory that we call obstructive shock. And essentially, obstructive shock is just that. It's an obstruction that impacts the flow of blood due to one of various mechanical issues that are going on. One important thing to note is that while the pathophysiology behind the mechanical causes are certainly different, the end result is ultimately the same thing and is very similar to what you would see in cardiogenic shock, which is that pump failure.

So in this lesson, it's going to be a little bit different in the sense that we're going to talk through each of these causes and at that time go through the pathophysiology of what's happening, talk about the signs and symptoms. diagnosis and treatment before moving on to the next one. And so with that said, let's go and move on to our first cause of obstructive shock, which is going to be tension pneumothorax. And as always, I've got a drawing to help guide us through this.

So let's talk a little bit about tension pneumothorax and what exactly is happening. So here we have our lungs. And typically we have our chest wall that runs along here. And typically we have the intrathoracic space here, which goes between our lungs and our chest wall. And this is normally an airtight seal.

And this is really what helps to keep the lungs inflated. And so normally in this space here, the pressure that's in there is less than the pressure that's inside of the lung. And that's what allows the lung to expand. But what can happen sometimes is that cavity gets opened up and exposed to the outside air.

And that air begins to come in and fill in this space. And eventually that decrease in pressure begins to go away. And what happens is that air will begin to fill in that space and change the pressure difference.

And with each successive breath, the lung will get smaller and smaller, and that pressure will continue to get greater and greater on the outside of the lung. And ultimately, if either severe enough or left to go on long enough, the lung can completely collapse. And part of the issue is that this air has no way to escape back out. And so as the air continues to build and build, it continues to put more and more pressure inside the cavity and ultimately can lead to the collapse of the lung.

and even more severe issues related to shock. There can be multiple causes of this, but some of the most common are going to be some sort of traumatic penetrating injury, and even positive pressure ventilation can cause an injury that allows air to escape into this cavity and ultimately leading to tension pneumothorax. And really what's going on in this process is as that pressure builds up, we begin to see pressure exerted this way.

And there's a few different things that are going to happen as a result of that. Part of it is we're going to be putting pressure on the vena cava, and that's ultimately going to cause that to narrow down and lead to a decrease in the return of blood to the right atrium. And this ultimately will decrease our preload and our cardiac output.

In addition to that, the pressure is also going to be pushing and putting pressure on the heart itself. which is going to constrict that heart, which ultimately can prevent the filling, as well as the contraction of the heart, again, leading to a decrease in cardiac output and ultimately our shock state. And depending on the cause and the severity, this can either happen very slowly over time, or sometimes this can come on quite quick and sudden.

And so some of the signs that you'll see in a patient tension pneumothorax probably the first and most notable sign is going to be a deviated trachea and what happens is again due to that pressure that trachea is going to deviate away from the side that the tension is developing on you also can see a hyper expanded chest on the side of the tension and on that side you're going to have an increase in a percussion sound as well as either decreased or in the case of a completely collapsed lung absent breath sounds. You're also going to see very little movement of the chest wall with respiration on that side. Along with this, you're going to see increased respirations and tachypnea as well as hypoxia.

And in addition to this, all the classical signs that you would see with a patient in cardiogenic shock. So in order to diagnose this, there's really two main things that you're going to look for. The first is going to be that tracheal deviation and it's important to note that this is away from the side that the tension is developing on and the second is going to be a chest x-ray and in the case of attention pneumothorax it's going to be very obvious because you're going to have nothing but black black space where the lung should be on the side that's affected now in terms of treatment when we talk about treatment one of the very interesting things about most of the cases of these various causes of obstructive shock, that if you relieve the obstruction oftentimes, and oftentimes very quickly, the shock can be completely stopped.

And so when we talk about the treatment for the tension pneumothorax, again, there's primarily two things that we look for. One, and this is more often in a field environment, but you have needle decompression. And this essentially inserts a needle into that thoracic cavity, allowing the air to escape and relieving that pressure.

And more commonly within the hospital setting, you're going to have a chest tube insertion. But one really important takeaway with this is sometimes this can progress very quickly and have very severe consequences. That this can be a very life-threatening situation, which can cause your patient to go into full-on shock.

rapidly progress to PEA and possibly even death. So now moving on to the next cause of obstructive shock, we're going to talk about cardiac tamponade. And so like with everything else, let's go and do a quick primer as far as what's happening. So what's happening here is normally we have our pericardial sac, and that goes around the heart and typically we have just a little bit of fluid in there for lubricating and allowing the heart to move freely. But what can happen sometimes is we begin to get a buildup of, and this fluid can come in many forms, you know, it can be just plasma volume.

In some severe cases, you can have buildup of pus from infection, but probably one of the more common ones is going to be a buildup in the accumulation of blood. And so again, what happens is as that fluid collection builds and grows, that the heart loses its ability to expand. And so this ultimately leads to a decrease in the chamber size, which ultimately means less blood is ejected each time the heart beats. In addition to that, the pressure that's exerted on the heart is going to prevent the flow of blood into the chamber, decreasing that venous return to the heart, again impacting our cardiac output. And when it comes to talking about cardiac tamponade, it really does not take that much fluid in order to start seeing some severe consequences and ultimately a shock state.

And so when we have our patient who is experiencing shock as a result of cardiac tamponade, there's a couple key things that we would be looking for. Again, in addition to all the typical cardiogenic shock signs that we would see, one telltale sign that we're dealing with cardiac tamponade is we're going to be looking for what we call Beck's triad. And essentially this is three things, muffled heart sounds, jugular venous distension or JVD, and hypotension. And even more specific in this hypotension, what you're going to see is a narrowing of the pulse pressure and the pulse pressure is essentially the difference between your systolic and your diastolic. So in order to diagnose cardiac tamponade, really the true gold standard is going to be with an echo or ultrasound of the heart.

And really the treatment for the tamponade is going to be pretty simple. We need to drain the fluid, and this can come in several forms. If your patient has had open heart surgery, it may be an adjustment of the chest tube. This may mean a pericardial synthesis or potentially even a pericardial drain. And again, just like with other forms of obstructive shock, oftentimes relieving the obstruction will completely resolve this state of shock.

Alright, so the next cause of shock that we're going to hit on very briefly is what we call constrictive pericarditis. And again, we have that pericardial sac. And what can happen here is over time, either due to infection or scarring, that this can become thickened and rigid, and this can put pressure in on the heart. And again, ultimately reducing the heart's ability to fill and beat properly, resulting in decreased cardiac output and ultimately a shock state.

And just to real quickly hit here, just some of the Treatment modalities that you might see would be things such as NSAIDs for anti-inflammatory, steroids as well, and in some cases this may lead to surgery and having a pericardectomy. And that will be the extent of what we talk about with constrictive pericarditis. All right, the next one that we'll talk about here is aortic stenosis. And essentially what happens here is if we look at our aortic valve, normally we have our three leaflets. And what can happen is over time, calcium can build up here.

And this calcium can prevent either the valve from opening or even closing smoothly. And so over time, if this calcium continues to build up, we can begin to severely narrow and limit the amount of blood that can go out into the aorta. This again ultimately is going to decrease our cardiac output and can lead to a shock state.

And like with all the others, classic cardiogenic shock signs are what we're going to be looking for. One thing that you will often notice is that they have a positive murmur. And just as with cardiac tamponade, Our gold standard for diagnosing this is going to be with an echo.

And finally, our treatment of aortic stenosis is really going to involve just a couple of things. We can do a valvuloplasty, which essentially attempts to reopen this narrowing. You can also look to get a new valve. And this can either be done with open heart surgery, or oftentimes these days we're looking at less evasive means such as a TAVR, which is essentially the placement of a new aortic valve via a catheter. And sometimes this doesn't require a new valve, but just going in via open heart surgery and doing a valve repair.

But ultimately though, if we fix the underlying cause and we restore that outflow tract, then oftentimes those signs of shock can dissipate quite quickly. All right, and so the last of these causes of obstructive shock that I'm going to talk about is something that we call a pulmonary embolus. And so what happens...

in the case of a pulmonary embolus is there can be a couple different things that can go on. Probably the most common form is patient developing what they call a deep vein thrombosis, and this is where a large clot that is formed and a deep vein, typically in the legs, breaks off and travels into circulation. Sometimes in the case of trauma and large bone fractures, you can end up with a similar process, but with what they call a fat embolus, and this can also break free and enter the bloodstream, just like the DVT will. And so what happens is, as these enter the bloodstream, they flow relatively freely into the right side of the heart and can enter into the pulmonary vein on their way to the lungs. And what happens here is the embolus will never make it to the left side of the heart.

It's never going to pass through the capillary bed, so we don't ever have to worry about this going to the left side and potentially into arterial circulation and potentially causing a stroke. But a very severe situation can arise depending on the size of the embolus. So the first of these is if it's large enough, it can just about occlude off one of the sides of the pulmonary circulation.

And this thus would severely limit the amount of blood flow that's going through here and ultimately returning back to the left side of the heart. And potentially, if this embolus is large enough, that this can lead to a shock state. But potentially even more important and even more severe is what we call a saddle PE. And that's essentially where you end up with some sort of embolus so large that it sits in the saddle of the pulmonary vein and completely stops all blood flow or the majority of the blood flow from continuing. past the right side of the heart.

And as you can imagine, this is a pretty severe situation that they would find themselves in. And in fact, 25% of the people that have this saddle embolus will experience sudden death. And again, with a PE, you're going to see all those same cardiogenic shock signs, but you may also notice increased respiratory rate and pallor or cyanosis. due to the lack of oxygen delivery to the blood.

Now there are a couple different tests we can use to diagnose. The first of these is going to be what we call a VQ scan, and this is looking for a VQ mismatch, or a ventilation and perfusion mismatch. But the other one, and again the more gold standard option, is going to be a CT angio.

And that will give you a clear picture of if there is a PE and exactly where it is and how big it is. And finally, to talk about the treatment for a PE, you really have two options available to you. You can dissolve it. This is going to be with TPA, TNK, heparin to prevent the forming of more clot.

or to remove it, so essentially to have an embolectomy. And this sometimes can be done in procedural sites such as interventional radiology or may require open heart surgery in order to go in there and remove that embolus. And again, especially in the case of a large PE, as soon as you can remove that embolus, oftentimes you can see that shock state resolve fairly quickly.

Alright, so that pretty much concludes our coverage of the different causes of obstructive shock. In each case, we went through an explanation of what exactly was happening, what you would be looking for, some of the diagnostic procedures, as well as the treatment for each. Again, the key takeaway, though, is that ultimately these are leading to a state of pump failure, and so the manifestation of obstructive shock is going to look oftentimes identical to cardiogenic shock, and it is only going to be through some of the other...

diagnostic tests or a few signs and symptoms in some cases that would help you distinguish that this is a form of obstructive shock. And ultimately, the biggest thing is to resolve that underlying cause and oftentimes your patient will make a very rapid recovery. All right, and so with that, I will go ahead and conclude this lesson. As always, I want to thank you for watching the lesson today and I really hope that you found this informative. If you liked the video and you did find it useful, please make sure and hit that like button below.

It really helps to spread the word about our channel. And in the comments below, tell us your favorite part, or feel free to ask us any questions that you may have had about this lesson. Finally, make sure and check out our next lesson in this series, which is going to be covering distributive shock, and specifically neurogenic and anaphylactic shock.

Or feel free to check out another one of our great series of lessons on hemodynamics. As always, thanks for watching and we'll see you in the next lesson.

Transcript for:Understanding Obstructive Shock Causes

Transcript for:
Understanding Obstructive Shock Causes