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Current time:0:00Total duration:9:47

Video transcript

so I want to create one final video on shock and this is the video to really compare all the different types of shock and see how you can differentiate between them now this will be an advanced coverage of all the different types of shock so most of my detail will be very brief and give you a general gist of the type of shock but of all of these I want to look at four different values the first is cardiac output and of course cardiac output is how much fluid how much blood the heart puts out per minute so it's usually measured in liters per minute or milliliters per minute SVR stands for systemic vascular resistance so that's resistance of all the blood vessels in the body and the two of these cardiac output and systemic vascular resistance equal blood pressure so usually in shock when one value goes down the other will go up to try to compensate unless both of them are shut down cardiac output and systemic vascular resistance also provide information on tissue oxygenation if they're decreased tissue oxygenation can be decreased as well bcw P stands for pulmonary capillary wedge pressure and this is measured with a pulmonary artery catheter it tells you how well the heart is able to pump fluid forward if the heart is struggling or if there's some blockage or something preventing blood from being pushed forward by the heart then P C WP pulmonary capillary wedge pressure will be elevated and lved V stands for left ventricular end-diastolic volume it's the volume of blood in the left ventricle at the end of relaxation basically it's how much blood is in the left ventricle just before it squeezes out so this will also be elevated in a heart that is overloaded with fluid and last of all the value M vo2 which stands for mixed venous oxygen saturation this will usually be low when the tissues have extracted a lot of oxygen this is measured in the right atrium so it's a way to average out the oxygen content and in the blood and so if tissues and the capillaries are able to extract oxygen the total amount of oxygen going back to the heart will be decreased so that would be a decreased mixed venous oxygen content and vice-versa if the tissues are unable to extract oxygen oxygen will be left in the bloodstream and this value will be elevated okay so that's the basics let's go ahead and get started on this so cardiogenic shock is an issue with the heart's ability to pump so right away we know that cardiac output is going to be decreased pretty severely depending on how severely the heart muscle is impaired with a decreased cardiac output the blood vessels are going to clamp down and so you'll have an elevated systemic vascular resistance in an attempt to return blood back to the heart and restore blood pressure the heart's inability to function leads to backup of fluid and usually this accumulates in the heart so you'll see an elevated pulmonary capillary wedge pressure as well as the left ventricular end-diastolic volume so these will be increased because blood is not squeezed out of the heart properly last of all mixed venous oxygen content will be lower and that's because since blood is not flowing as quickly because the heart is shut down any oxygen that remains in the blood is pulled furiously out by the tissues and so you'll see a lower content of oxygen when Blood returns to the heart now obstructive all I'll rush through really quickly because it's pretty much identical to cardiogenic shock instead of the heart being affected it's something outside of the heart that's preventing fluid from being squeezed forward so of course blood is left in the heart meaning a piece ewp will be elevated and going back over here fluid can't be pushed out of the heart because of some sort of obstruction whether this is a pulmonary embolism preventing blood from getting from the right side of the heart to the left side of the heart or if it's cardiac tamponade or aortic stenosis or ear or any of that and the blood vessels will compensate by trying to increase vascular resistance and last of all tissues are trying to pull out oxygen furiously so it will see a low MV o2 to really differentiate these two it's important to know a patient's history as well as the symptoms that they're experiencing and the onset of the symptoms as well for example if a patient has history of heart attacks it may be more likely that cardiogenic shock is the cause so you'll go through your different diagnostic tools to determine whether it's cardiogenic or obstructive shock now hypovolemic shock the issue is low blood volume so because of low blood volume there is a low amount of blood that can be squeezed forward from the heart low fluid return to the heart means low cardiac output low delivery of oxygen and because of this low blood volume blood vessels are trying to clamp down and so systemic vascular resistance will be very elevated the fluid accumulation in the heart that's left over will actually be very low because right it's hypovolemic low volume in the body and tissues we'll be extracting oxygen furiously leaving the MV o2 to be much lower next neurogenic shock causes impaired sympathetic response to the heart and the blood vessels so you have very low blood pressure because both the heart and the blood vessels are getting low sympathetic tone and if no in neurogenic shock you have bradycardia low heart rate this is very unique to neurogenic shock as in all the other shocks heart rate is increased to try to compensate for the low blood pressure and there should really be no change in ventricular volume and there will be a decrease in mixed venous oxygen essentially the circulatory system collapses so blood flow slows way down and so oxygen is exposed to the tissues longer as blood traverses through the blood vessels giving more time for oxygen extraction next we have septic shock now the cause for shock in sepsis is the immune system the immune system responds to infective material and causes stomach vascular dilation vasodilation so vascular resistance drops tremendously to compensate for this the heart initially tries to pump faster but as time goes on as a patient is exposed to sepsis for a longer period of time the immune molecules can paralyze the heart and cause damage which will lead to decreased cardiac output so cardiac output can either be elevated initially or lower in later stages of septic shock the fluid load on the heart is really not affected maybe a little bit lowered and oxygen extraction can either be elevated or decreased and the reason you might have an elevated M vo2 mixed venous oxygen saturation is because the tissues aren't extracting it properly septic shock causes a lot of swelling throughout the body and this can make it difficult for oxygen to be delivered to the tissues a lot of fluid is accumulating just outside of the blood vessels and so oxygen has to travel a longer way to get from the blood vessels to the tissues that need the oxygen and so that's a perfect segue into anaphylactic shock there's also increased swelling and that's one of the major symptoms of anaphylactic shock so oxygen cannot be distributed to the tissues properly and also an anaphylactic shock you have a large lowering of vascular resistance the blood vessels throughout the body dilate which is very similar to septic shock now cardiac output will be elevated in an attempt to counteract the decreased resistance and the pulmonary capillary wedge pressure will be the same maybe a little bit decreased now last of all we have dissociative shock and this is a very interesting shock because both cardiac output and resistance are going to be increased the tissues are not getting oxygenation because oxygen cannot dissociate off of red blood cells so because of that the body attempts to increase the heart rate and improve cardiac output as well as clamp blood vessels down to distribute oxygen properly however regardless of these changes red blood cells cannot dissociate from their oxygen and so that is causing tissue starvation so looking over at M vo to the tissues will pull out any oxygen they can from the blood so MV o2 will be lowered free-floating oxygen in the plasma in the blood plasma will especially be low since tissues are not getting their oxygen from the red blood cells and finally the pulmonary capillary wedge pressure or the fluid overload of the heart will be about the same no real change so I encourage you to go back and look over this chart and attempt to do it on your own to really reason through each of these types of shock to understand how they cause decreased oxygen perfusion