Epinephrine works by binding to alpha 1 and beta 1 receptors in the body to increase vasoconstriction and increase the positive inotropic and chronotropic effects of the heart. We remember this because of its use in cardiac arrest patients, asthma patients, bradycardic patients, and hypotensive patients. We’ve all used Epinephrine in varying concentrations either IM, SQ, IV, or IO for cardiac arrest calls, anaphylaxis calls, and some respiratory calls because it also affects beta 2 receptors for smooth muscle relaxation in the respiratory tract, and nebulized in pediatrics for croup.
Why would we use an epinephrine drip? These are useful in cases where the patient:
- Continues to be hypotensive or bradycardic despite doses of Atropine or pacing
- Is hypotensive after a cardiac arrest because the body is still not regulating blood pressure on its own and still needs help vasoconstricting
- Is experiencing severe anaphylaxis and is not responding to IV doses of Epinephrine or needs repeat doses and is also not responding to fluid boluses.
What are contraindications or concerns for starting an epinephrine drip? There are no contraindications for Epinephrine in the emergency setting, however, there are multiple situations where Epinephrine use may exacerbate another issue. If a patient has coronary artery disease or is experiencing angina this may worsen due to the vasoconstriction, the patient may also develop a cardiac arrhythmia. The patient may also develop pulmonary edema due to increased cardiac output, decreased renal output due to renal blood vessel constriction, or strokes due to cerebral artery constriction. There is little risk with a small amount of extravasation of an epinephrine drip because it is the same or more dilute than what is used for localized injections for anesthesia. However, since it does cause vasoconstriction it may cause some pallor or coldness to the area, especially in the hands and feet.
Now that we have weighed the risk versus benefit of an Epinephrine drip and we have decided to administer one, what dose do we use and how do we mix the infusion? Well, that depends on what we are treating. For bradycardia that is not responding to Atropine or pacing, we administer 2-10 mcg/min IV or 0.1-0.5 mcg/kg/min IV. For hypotension secondary to cardiac arrest or diffuse vasodilation we use 0.1-0.5 mcg/kg/min IV. For anaphylaxis, you can also use 5-15 mcg/min with IV fluids. The most common way to mix up the infusion is to add 1mg of Epinephrine to 1L of D5W or Normal Saline. This gives you a concentration of 1 mcg/ml. So if you have a 100 kg patient who is bradycardic and hypotensive after a cardiac arrest and you are going to start at 0.1 mg/kg/min what is your drip rate? Multiply the 100 kg times the 0.1 mcg/kg/min to get a dose of 10 mcg/min. Your concentration is 1 mcg/ml so you need 10 ml/min. If you are using a 10 gtt/ml set you to multiply 10 ml/min times the 10 gtt/ml to get 100 gtt/min.
So what if the patient is not responding to the drip, how long before you can increase the drip rate and by how much? The drip rate can be increased every 10 minutes and by 0.05 -0.2 mcg/kg/min because Epinephrine is a potent vasoconstrictor. Titrate the drip until the patient is no longer bradycardic or hypotensive. Use the least amount of medication necessary to minimize adverse effects.
In conclusion, an Epinephrine drip can be useful in patients that are not responding to first-line medications due to its potent vasoconstriction effects and its positive inotropic and chronotropic effects on the heart. Treat the patient with first-line medications first and fluid resuscitates the patient and use an Epinephrine drip if not effective.
WE ALSO CANNOT STRESS THIS ENOUGH, ALWAYS FOLLOW YOUR LOCAL PROTOCOLS FIRST AND FOREMOST, OUR CONTENT IS INTENDED FOR STUDY PURPOSES NOT TREATING PATIENTS IN THE FIELD.