Epinephrine: Fight or Flight Saves Lives
Ashley Innes
Keyano College
October 5, 2018
Most people today know at least a little bit about the life saving drug epinephrine. Chances are, you or someone you know has an auto injector of it to use in case of an emergency and various media campaigns in the past have sought to inform the public on when and how to use it. As a molecule it’s formula is C9H13NO3 and it’s chemical name is (R)-4-(1-hydroxy-2-(methylamino)ethyl)benzene-1,2-diol (New World Encyclopedia [NWE]. 2008). Luckily, as that name is quite a mouthful, it is also referred to as epinephrine, it’s generic name. As well as a number of trademarked names including Adrenalin®, and EpiPen® (Keyano College Prehospital Care Programs [KCPCP]. 2018). Regardless of what name you use for it the most important thing about epinephrine is how invaluable it is in treating anaphylactic reactions and a number of other time sensitive emergencies that could otherwise end very badly.
Anaphylaxis, meaning possible exposure, followed by either sudden respiratory symptoms or a sudden drop in blood pressure, or both skin or mucus signs AND gastrointestinal upset (Alberta Health Services [AHS]. 2018) indicates the need to treat with epinephrine without delay. In an emergency there are no contraindications as reversing the symptoms of anaphylaxis is critical for the patient’s survival.
When someone is allergic to something the body is overreacting to that substance. The reaction can be anywhere from mild to life threateningly severe. In cases of severe hypersensitivity the immune system signals the body that getting the allergen out and making sure no more gets in is the most important task; to the point that breathing and moving blood actually become secondary. All the blood vessels dilate and become more permeable, leaking fluid into the tissues which causes swelling. It stimulates the production of mucus from the mucus membranes to trap antigens so they cannot get into the bloodstream. (Bledsoe, Porter, Cherry, and Clayden. 2006). From blood vessels letting go, fluid leaking into the cells and the production of mucus there is a critical loss of blood pressure. On top of that, in an effort to protect the lungs from contamination bronchoconstriction shrinks the airway, often to the point of apnea.
Epinephrine is a naturally existing hormone in the body. It is part of the sympathetic nervous system and is responsible for our fight or flight responses. When the brain perceives a threat it makes dealing with that threat priority 1 and it sends that message to the body by stimulating the adrenal glands to release epinephrine into the blood stream. Epinephrine then stimulates beta1 receptors causing positive chronotropic and inotropic effects on the heart; beta2 receptors cause bronchodilation and central vasodilation, and Alpha1 receptors which cause peripheral vasoconstriction (KCPCP. 2018). It may be surprising that one hormone does so many different things, but the epinephrine is just the messenger to the cells that “this body needs to get ready to MOVE” and they react in the way that best facilitates that need. It is the receptors keyed to respond to the presence of epinephrine that dictate what that response will be. Different epinephrine receptors will cause different, or even opposite, physiological reactions depending on where they are in the body. It is the body’s way of swiftly reallocating its resources in order to prioritize fighting or escaping the current immediate threat (Crash Course. 2018).
Medical epinephrine is the same as the hormone released when the sympathetic nervous system kicks in. Which is why it is in a class of drugs called sympathomimetics (Class Slides. 2018). Because the physiological reactions to epinephrine in the blood are closely matched to what we need to have happen to reverse anaphylaxis, by introduction epinephrine into the body we can “mimic” the sympathetic system and let the body do what it does naturally.
In a Basic Life Support (BLS) unit, epinephrine’s star role is as a treatment of severe allergic reactions resulting in anaphylaxis. Adults receive a dose of 0.3mg injected intramuscularly which can be repeated after 5-10minutes if necessary up to a total of 3 times, or 0.9mg. Children, being smaller, have a smaller and more precise dose calculated by the patients weight; it is 0.01mg/kg IM to a single dose maximum of 0.3mg, which can also be repeated every 5-10minutes to a total maximum of 0.9mg (KCPCP. 2018). If a patient is experiencing life threatening anaphylaxis there are no absolute contraindications for the administration of the drug. Extra care does need to be taken if a patient has a known hypersensitivity to epinephrine or cardiovascular disease.
Advanced Life Support (ALS) units have the same protocols when encountering a patient presenting with anaphylaxis, however their scope of practice allows them to utilize epinephrine far more extensively than that of BLS responders. ALS can give epinephrine intravenously, which gets it into the bloodstream immediately. This can be used to treat people in cardiac failure, as a treatment for shock, or serious respiratory depression. They can also give epinephrine to children presenting with stridor and impending respiratory failure using a nebulizer (AHS. 2018).
Though epinephrine is an invaluable resource that has saved countless lives, there are risks involved with its use. Even if it is administered perfectly there will be side effects. These include anxiety, tremors, heart palpitations, nausea and vomiting; and those are the ones that are expected! Epinephrine overdose has far more serious effects. In a report titled “Epinephrine” (2018) on the site Acutetox.eu they list the effects of epinephrine overdose by what part of the body is impacted. Some of the most frightening items are “hypertension, myocardial infarction [and] dysrhythmias.”… “pulmonary edema, and pneumothorax”…”numbness of hands and feet, tremors [and] insomnia” …”acidosis”
“Death after epinephrine overdose is mostly caused by either cerebral hemorrhage or cardiac arrest/arrhythmia” (Acutox.eu. 2018. Epinephrine. Para. 5).
The effects of epinephrine overdose are very serious and the best help for a patient experiencing them is ALS support and the hospital. Both of whom have medications that can assist in sympathomimetic overdoses, but that are outside of the scope of practice for other emergency personnel (AHS. 2018). Considering how dangerous improper use can be, perhaps some would agrue against the availability of personal injectors such as EpiPen®. However personal injectors help a lot more people than they hurt. They are preloaded and prescribed to a specific person and their doses are set and cannot be altered. So overdoses are quite uncommon. The majority of cases of epinephrine toxicity are actually caused by dosage error in the prehospital and hospital setting (Acutox.eu. 2018. Epinephrine. Para. 4).
This highlights the critical importance of EMS and HMS workers being diligent when giving medications every single time, whether it is the first time or the thousandth. Know what you are giving and where to find the information needed to ensure it is done right the first time, every time.
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References
RxList. (2018, October, 2). Adrenalin (Epinephrine): Side Effects, Interactions, Warning, Dosage & Uses. Retrieved October 2, 2018 from https://www.rxlist.com/adrenalin-drug.htm#description
New World Encyclopedia. (2008, April 2). Epinephrine. Retrieved October 3, 2018 from http://www.newworldencyclopedia.org/p/index.php?title=Epinephrine&oldid=679468.
Sympathetic Nervous System: Crash Course A&P #14. (2018). YouTube. Retrieved 3 October 2018, from https://www.youtube.com/watch?v=0IDgBlCHVsA&list=PL8dPuuaLjXtOAKed_MxxWBNaPno5h3Zs8&index=14
Parasympathetic Nervous System: Crash Course A&P #15. (2018). YouTube. Retrieved 4 October 2018, from https://www.youtube.com/watch?v=qqU-VjqjczE
Adrenaline or Epinephrine, Noradrenaline, and the Stress Response. (2018). Owlcation. Retrieved 5 October 2018, from https://owlcation.com/stem/Adrenaline-Epinephrine-and-the-Adrenal-Gland-Stress-Response
(2018). Acutetox.eu. Retrieved 4 October 2018, from http://www.acutetox.eu/pdf_human_short/96-Epinephrine%20revised.pdf
Epinephrine. (2018). Statkit.com. Retrieved 4 October 2018, from https://www.statkit.com/Epinephrine-1mL-1to10k-needle-safe
AHS Protocols. (2018). Ahsems.com. Retrieved 5 October 2018, from https://www.ahsems.com/public/protocols/templates/desktop/#home
Keyano College Prehospital Care Programs.(2018). Medications Module. Retrieved Oct 2018.