If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Main content
Current time:0:00Total duration:8:30

Video transcript

anaphylactic shock is probably one of the shocks that most people are familiar with it's also known as anaphylaxis anaphylactic shock is an allergic reaction that's severe enough to cause shock and of course shock is decreased tissue perfusion or in other words decreased oxygenation of tissues there are a number of different things that can cause an allergic reaction for example bee stings can cause an allergic reaction peanut allergies food allergies pollen can cause allergic reactions and so can certain medications as well now of course allergies can be either very mild and seasonal such as hay fever and sometimes allergies can be so severe that it can cause shock but how does it cause shock well first of all to answer that I want to acknowledge that there are two types of anaphylaxis those that are immune illogic and those that are non immune illogic and I'll go ahead and start with immunologic anaphylaxis because that's actually the most common type in immunologic anaphylaxis there's some sort of allergic agent whether it's poison from a bee sting or food allergy that somehow gets into the system and whatever this material is it's known as an allergen because it generates an allergic response so when this allergen first gets into the body it will interact with b-cells and not be cells like the insect that'd be right up here but b-cells as in the letter B now these cells are the antibody creating cells of the immune system they create antibodies and antibodies are essentially a little Y shaped protein that is used like a signal marker to find something that's foreign foreign material so in this case the antibodies will be reacting to the allergen now antibodies that are created in response to an allergen are known as IgE IG e stands for immunoglobulin E globulin means protein and immuno just means immune so really its immune protein and the classification is e now the reason I want to emphasize this is because IgE specifically docks on two other immune cells which are known as mast cells these mast cells are mediators of the immune system so what ends up happening is once I GE is created it will dock onto these mast cells so this all occurs when a person is first exposed to an allergen and this is called sensitization the immune system is sensitized to this allergen so the next time that this allergen comes along it will create a rapid allergic response the allergen will dock on to these antibodies and when they do the mast cells activate and when mast cells activate two main things happen first of all mast cells release immune molecules known as cytokines cytokines are essentially used for cellular communication so mast cells communicate with other white blood cells and tell them to come over so what ends up happening is these white blood cells continue to recruit more white blood cells and it's a cycle that that creates more and more white blood cells being recruited and activated in response to these allergens now that activation of both the mast cells and the immune cells causes release of another molecule known as histamine now histamine is a potent vasodilator in other words it dilates blood vessels so here i with the dotted line i'm showing a blood vessel size before and after histamine the diameter of the blood vessel increases now this is happening in the blood stream in the entire body and it causes a large drop in blood pressure so patients lose the function of their circulatory system and are no longer able to distribute oxygen and so that's how an allergy causes shock and also let me note that histamine causes the blood vessels to become leaky so fluid escapes the vascular space which causes swelling to occur all throughout the body so a patient has massive swelling along with a massive drop of blood pressure now the second type of anaphylaxis is called non immuno logic now non immuno logic anaphylactic shock is essentially the same as immunologic shock it's just the pathology is slightly different instead of mast cells being stimulated by IgE the allergen specifically targets the receptors on the mast cells and so you get the same process of histamine release as well as cytokine release which of course causes the super immunological response as more white blood cells are recruited and then also causes this drop of blood pressure so what are the symptoms that we see in anaphylactic shock the symptoms are going to be characterized by the actions of histamine so a patient with anaphylactic shock has this major drop in blood pressure due to vessel dilation so we'll see flushing of the skin as blood vessels dilate and blood starts to saturate in the skin and swelling as fluid is getting outside of the blood vessels and itchiness which is also caused by histamine release so these are all symptoms that you would come to expect from an immune response you may see other various symptoms such as rhinorrhea which is a runny nose and this is caused by vessel dilation in the nasal vasculature so you have an overactive release of fluid but the symptom that I really want to get to occurs with the lungs is to me not only causes vessel dilation one of its most serious symptoms is bronchospasms spasms of the bronchi the main air passages to the right and left lungs so these bronchospasms make it difficult for a patient to breathe what makes it worse also is that swelling can be occurring in the throat as well which can close off the airway making it even more difficult to breathe so a patient comes in who's non-responsive he's not breathing and you check and find that the patient has a very low blood pressure so what do you do do you order lab tests no that's a terrible idea this patient is having a severe bout of shock it should already be apparent based off of the clinical symptoms that this patient has especially the low blood pressure severe low blood pressure should indicate that right away something needs to be done so you progress right to treatment and treatment is based off of the ABCs airway breathing in circulation so number one you want to establish the airway if a patient is not breathing you want to give them a hundred percent oxygen so you can fill up their lungs and ventilating the patient with a bag mask to push air into the lungs may be one of the first ways to respond to a patient who has anaphylactic shock along with this the blood pressure needs to be maintained there's one medication that's especially effective at maintaining blood pressure in patients with anaphylactic shock and that's epinephrine first of all of course patients have these very dilated blood vessels now epinephrine has strong sympathetic activity so it acts in a way to constrict blood vessels back down to maintain blood pressure so this directly counteracts what histamine does to blood vessels epinephrine also affects the lungs and causes Branko dilation so it opens up the Airways so this is important to allow airflow back into the lungs now to also maintain blood pressure IV fluids will help fill up the vascular space so these are the main ways to treat a patient with anaphylaxis and along with this you can give anti histamines to really directly counteract the effects of histamine in the body but of course let me emphasize that epinephrine and IV fluids are the mainstay of treatment because they act to immediately reverse the low blood pressure and restore a patient's circulatory system