ACLS-certified clinicians know that epinephrine is one of the most common drugs used during a cardiac arrest. However, it is also important to understand how this drug works, as well as its background information and potential side effects in the event you need to administer it.
First introduced into the ACLS algorithm in 1974, Epinephrine is now one of the primary drugs used in advanced cardiac life support situations. Let’s take a closer look at this drug and how it applies to different life support scenarios.
Epinephrine is a drug that has many preparations and applications and many routes of administration. It functions as a hormone in the body, mimicking the effects of adrenaline. Epinephrine is FDA-approved for many treatment situations and is commonly used off-label for other situations.
Some of these are:
Epinephrine is also used as an emergency rescue drug for lethal cardiac rhythms, which is the primary focus of this article. These rhythms include:
Epinephrine was the first hormone to ever be isolated for use as medicine and has been in continuous use for over a century. The compound was first isolated and marketed in 1900 by Farbwerke Hoechst. Rival companies soon followed, some with slightly different preparations. By 1906, production of synthetic epinephrine began, leading it to become cheaper and more widely available. At this point it was primarily used as a vasoconstrictor to stop bleeding, raise blood pressure for patients in shock, and treat asthma attacks.
Today, epinephrine is sold under many recognizable brand names, including EpiPen, Adrenalin, Auvi-Q, Primatene Mist, Marcaine, and several others. It can be used topically, as a nasal mist, eye drops, SQ or IM injection, respiratory inhalation, and IV/IO preparation.
Epinephrine (also known as adrenaline) is both a hormone and neurotransmitter. It is a lightweight molecule with the chemical formula C9H13NO3. It is a sympathomimetic catecholamine that works with both alpha and beta-adrenergic receptors. Smaller doses primarily work on beta receptors, while larger doses are more selective for alpha receptors. The drug works on effector cells and mimics the sympathetic nervous system to produce the same actions — except for effects on facial arteries and sweat glands.
Physiological effects of epinephrine can include:
Epinephrine is metabolized and excreted through the urine in the form of sulfates and glucuronides. The drug has a short half-life; however, absorption and effects of the drug vary according to route of administration. When administered intravenously, epinephrine produces an immediate and intense response, but disappears quickly. The half-life is about 2-3 minutes.
Epinephrine is safe for both children and adults in appropriate doses. It is unknown if epinephrine can harm the fetus when administered to pregnant women. However, it has been found to be teratogenic when given to rats in high doses. Epinephrine should only be given to pregnant women in life-threatening situations.
Epinephrine, a vasopressor, is used as part of the ACLS treatment algorithm for its strong vasoconstrictive effects, and secondarily for its ability to increase cardiac output. These effects cause an immediate improvement of perfusion to the brain and heart, which is critical during life-threatening cardiac and shock events.
Studies have shown that epinephrine and vasopressin (an alternate drug) improve rates of return of spontaneous circulation (ROSC) after cardiac arrest. However, vasopressin is no longer used in the ACLS algorithm because other studies suggested no additional benefit from administering vasopressin with epinephrine (as opposed to using epinephrine alone). Neither vasopressin nor epinephrine improve survival, so the overall clinical benefit when used while attempting to treat refractory cardiac arrest remains questionable.
As part of ACLS treatment, epinephrine is used in the following ways: (see Figure 1)
Figure 1: ACLS Epinephrine Dosing
|VF, pulseless VT, asystole, PEA||IV push/IO||1 mg||Every 3-5 minutes|
|IV infusion for symptomatic bradycardia||IV||1 mg in 500ml NS or D5W||Rate should be 2-10 mcg/min, titrated per VS|
|IV infusion for post-cardiac arrest hypotension||IV||1 mg in 500 ml NS or D5W||Rate should be 2-10 mcg/min, titrated per VS|
|VF, pulseless VT, asystole, PEA||ET tube||2-2.5 mg diluted in 10 ml NS||Give directly down the ET tube|
Side effects of epinephrine generally stem from its effects on the sympathetic nervous system, and should be transitory due to the short life of the drug.
The most commonly reported adverse reactions include:
Because Epinephrine increases heart rate and raises blood pressure, it also increases the heart’s oxygen demand. This drug should be used with extreme caution in patients suffering from a known cardiac blockage/myocardial infarction, as it can worsen ischemia.
Several drug classes can interact with epinephrine, causing unpredictable effects. Alpha-adrenergic blockers, antihypertensives, vasodilators, and diuretics can antagonize (or work against) the pressor effects of Epinephrine. On the other hand, beta-adrenergic blockers, monoamine oxidase (MAO) inhibitors, and catechol–o-methyltransferase (COMT) inhibitors can potentiate, or increase pressor effects. Vital signs and EKG should be monitored carefully during and after administration, especially when the patient is on multiple medications.
Epinephrine is also a powerful vasoconstrictor, which can cause vascular trauma in small vessels (such as capillaries in the fingertips). A large bore IV site should be used for administration, and clinicians should take care to confirm potency of the IV line to avoid extravasation into surrounding tissues.
If you would like to learn more about the drugs, ECG rhythms, clinical scenarios, and other topics related to ACLS, AMRI has study materials that can help you develop your understanding. Accredited by the National Board of Emergency Care Certifications (NBECC), AMRI has helped more than one million medical professionals earn their ACLS, BLS, and PALS certifications or recertifications since 1983.
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