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EPINEPHRINE

Category: Medical

Topic: Emergency Medications

Level: EMT

Next Unit: Anticoagulation and Antiplatelet therapy

17 minute read

Drug Profile: Epinephrine

Trade name: Adrenalin, Epi-Pen

Classification: Sympathomimetic

Mechanism of Action

A naturally-occurring hormone that acts directly on the alpha- and beta-adrenergic receptors found all over the body, but most importantly in the blood vessels. This causes positive inotropic (heart contraction strength) and chronotropic (heart rate) effects as well as increased systemic vascular resistance (constriction of the blood vessels). These effects combine to dramatically increase blood pressure.

Indications

Epinephrine is used when dramatic and immediate activation of the sympathetic nervous system is needed. In the EMS setting, this comes into play when circulation is compromised due to loss of cardiac output or loss of systemic vascular resistance. Note that both of these things will result in low blood pressure as they are a part of the blood pressure equation. 

Blood Pressure = (Cardiac Output) x (Systemic Vascular Resistance)

The loss of cardiac output refers to cardiac arrest and symptomatic bradycardia. If a patient in cardiac arrest is exhibiting a rhythm consistent with asystole, ventricular fibrillation, pulseless ventricular tachycardia, or pulseless electrical activity, the use of epinephrine is indicated. The other common indication is in patients whose heart is still beating, but is beating slow enough that it is causing hypoxemia, this is known as symptomatic bradycardia.

The loss of systemic vascular resistance is the other indication for epinephrine usage, specifically the condition of anaphylaxis; the extreme allergic reaction that results in specific individuals whose bodies are hypersensitized to specific allergens. Epinephrine acts on the sympathetic receptors in the blood vessels, causing them to clamp down, and in the heart causing it to beat faster and harder.

Finally, epinephrine is used in severe asthma attacks that are not responding to albuterol in the field, this use is very rare and is generally reserved for emergency departments.

Contraindications

Epinephrine should always be used for patients in anaphylaxis and in patients with cardiac arrest. There are rare hypersensitivities to epinephrine that leads to extreme increases in blood pressure and heart rate. Do not let fear of these conditions stop you from administering epinephrine when it is indicated.

Dosage and Route during Cardiac Arrest

During a cardiac arrest, the use of epinephrine is part of the ACLS algorithm, for review the timelines and dosing are reviewed below. Keep in mind that epinephrine can be administered through an endotracheal tube (ET) or into the veins (IV) each of which demands a different concentration for dosing. These amounts and concentrations should be memorized, as their rapid and appropriate use during ACLS is essential to patient outcomes. Use caution, as 1:10,000 (one-in-ten thousand) concentration is given via IV and 1:1,000 (one-in-one thousand) is given via endotracheal tube, mixing these up can be dangerous for the patient. The use of the IV route for administration is considered more effective, ET use should only be done until IV access can be obtained.

Intravenous

Adult: 1.0mg of 1:10,000 q 3 - 5 minutes

Pediatric: 0.01mg/kg of 1:10,000 q 3 - 5 minutes

Endotracheal

Adult: 2.0 - 2.5mg of 1:1,000 q 3 - 5 minutes

Pediatric: 0.1mg/kg of 1:1,000 q 3 - 5 minutes

Dosage and Route during Severe Anaphylaxis/Asthma Attack

Anaphylaxis and severe asthma attacks utilize the same algorithm for the administration of epinephrine. The Intramuscular (IM) method of administration is classically done via EPI-PEN, an autoinjector device that is designed to be usable by a victim themselves. In some jurisdictions, your ambulance may be equipped with these devices. If not, administration into the anterolateral thigh or deltoid can be done with any standard syringe and hypodermic needle (14 to 22 gauge 0.5 to 1.5 inch). Subcutaneous (SUBQ) administration is just as effective and only slightly slower in speed of onset, in obese patients, SUBQ administration may be required.

Adult Dosing: 0.3 - 0.5mg of 1:1,000 IM q 5 - 15 minutes,

if patient deteriorates 0.1 - 0.5mg of 1:10,000 IVP q 5 - 15 minutes.

Pediatric Dosing: 0.01mg/kg of 1:1,000 IM (6% to 19% require a second dose)

if patient deteriorates 0.1 - 0.5mg of 1:10,000 IVP q 5 - 15 minutes.

Deterioration in the setting of anaphylaxis or severe asthma attack is defined as unconsciousness, a drop of SPO2 below 92%, or suspicion for complete airway obstruction.

Dosage and Route for Symptomatic Bradycardia

Bradycardia is commonly asymptomatic, many elite athletes and elderly individuals have heart rates under 60 without any signs of hypoxemia. Symptomatic bradycardia, however, can be treated by epinephrine, with the goal of increasing the heart rate using the sympathetic receptors in the pacemakers of the heart. Note that Atropine is the first drug of choice for bradycardia, but many jurisdictions have epinephrine as the first line for EMS providers, due to a lower number of severe side effects. 

Pediatric Patients

In children with symptomatic bradycardia the same doses used in cardiac arrest apply, the exact ages in which this use applies depends on your local protocols. Some jurisdictions limit code doses of epinephrine for treatment of extremely young children only, while others will allow the use of alternative medications. As with cardiac arrest, note the difference in concentration between endotracheal and IV doses.

0.01mg/kg of 1:10,000 via IV every 3 to 5 minutes

0.1mg/kg of 1:1,000 through an ET tube every 3 to 5 minutes

Dosage and Route for Symptomatic Bradycardia (as an infusion)

In some jurisdictions, a continuous IV infusion of epinephrine will be the initial protocol mandated treatment for symptomatic bradycardia. This is also a  common backup treatment for jurisdictions where atropine is dosed in the EMS setting. Prepare an epinephrine infusion by mixing 1mg of 1:10,000 Epinephrine into 250 ml of NS. 

In adult patients, the desired infusion rate is 2 - 10 mcg/min

In pediatric patients, the desired infusion rate is 0.1 to 1.0 mcg/kg/min the dose chosen is often started low and titrated to patient response.