, 6 min, 1191 words
Tags: ems
I'm currently in the midst of an awesome EMT-basic course with EMT-Utah. It's been a blast so far. One of the things we really have to know inside out and upside down is medications: what they do, when and how to administer them, and how they can help or hurt a patient. Today I want to talk about epinephrine and albuterol and the situations in which you don't want to administer them.
First, a few definitions:
Indication: the reason you would choose to give a medication. For example, the indication for epinephrine is a system-wide allergic reaction, also known as anaphylaxis.
Contraindication: the opposite of an indication. That is, a reason not to give the medication. For example, hypersensitivity is a contraindication for almost every medication. In other words, don't give people medicine they're allergic to.
Action: what the medication does. Epinephrine constricts the veins and arteries in your periphery (e.g. fingers and feet) and dilates your bronchioles (tubes in your lungs that let air in and out) to make it easier to breathe.
Side effects: other stuff a medication does besides its main purpose. For example, epinephrine makes people antsy and nervous.
Epinephrine (affectionately known as "epi") and albuterol are two medications available to basic EMTs that can help a patient who's having trouble breathing. Both medications are sympathomimetics, meaning they mimic the sympathetic nervous system, meaning they will increase your heart rate and dilate your bronchioles, making it easier to get air in and out of your lungs.
Most people know epinephrine in the form of an EpiPen, a form of auto-injector that will inject the appropriate dose of epinephrine without having to fiddle around with syringes. What you might not know about epinephrine is that it's also naturally produced by the body. You may know it by its other name: adrenaline. So when someone uses an EpiPen, they're literally getting a massive adrenaline rush. The indication here: system-wide allergic reaction.
Albuterol is the active ingredient in emergency inhalers. If you've ever seen a young athlete rush to the side of a playing field and rummage through their bag to find their inhaler, this is the medication they're looking for. It's inhaled from a metered-dose inhaler (MDI) and its primary effect is dilating the bronchi, making it easier for air to get into and out of the lungs. Officially speaking, indications for albuterol are an asthma attack or difficulty breathing with wheezing.
At this point we've covered indication (why you'd give the medication) and action (what it does). Let's talk about side effects. Because epinephrine and albuterol are both sympathomimetics, they have similar side effects. Envision what happens when your fight/flight/freeze instinct kicks in: you get anxious and restless, and your heart rate and blood pressure go up. This is exactly it. The side effects of both epinephrine and albuterol are:
Well, that was easy.
Contraindications for epinephrine and albuterol are where I've historically gotten mixed up. The one thing they have in common is that if a patient is experiencing chest pain of cardiac origin (for instance, a heart attack), the last thing they need is for their sympathetic nervous system to kick into gear, making it harder for the heart to pump blood around the body.
Let's start with epinephrine. I already mentioned that it can spike your blood pressure. As a result, epi is contraindicated for patients with hypertension. The reason? Too high a blood pressure dramatically increases your chance of stroke or aortal aneurysm. Other than that, if you have a hypothermic patient, there are three reasons not to administer epinephrine:
Their immune system will react to allergens much more slowly than in a warm patient, so there's less need for epi immediately.
In hypothermic patients, an injection of epinephrine in the leg is just going to stay there, rather than distributing to the rest of the body, thanks to vasoconstriction.
Finally, epinephrine simply isn't metabolized at low temperatures. So it won't be useful. But also, if you inject someone with epi – or even repeat doses because you don't see an effect – when you warm the patient back up, all of that epinephrine is going to hit their system at once. Not a good plan.
And for albuterol, because it's not a naturally-occurring substance in the body like adrenaline/epinephrine is, we have to worry about hypersensitivity. Also, if a patient already has a very high heart rate (severe tachycardia), albuterol can further increase it. A very high level of tachycardia can lead to cardiac dysrhythmias, which can be anywhere from mild but weird-feeling to a life-threatening cardiac emergency. As a result, tachycardia is a (relative) contraindication for the use of albuterol.
If you're anything like me, you're now confused about why tachycardia is a contraindication for albuterol but not epinephrine. And similarly, why hypertension is a contraindication for epinephrine but not albuterol. What's going on here?
Let's talk hypertension first. Basically, epinephrine has a lot more "oomph" in mimicking the sympathetic nervous system, so it'll increase a patient's blood pressure much more than albuterol does. Thus, hypertension is a contraindication for epi but not for albuterol.
What about tachycardia? Surely if epi has more "oomph" than albuterol, tachycardia should be a contraindication for epinephrine too? The key thing I learned yesterday (thanks, Alyssa!) is the difference in half life between the two medications. Half life is a measure of how long it takes a medication to break down in the body – a longer half life means the medication sticks around longer. The half life of albuterol is measured in hours: about 4-6 hours, typically. The half life of epinephrine is measured in minutes: usually 2-7 minutes. So what's going on with tachycardia is that the risk of cardiac dysrhythmias is fairly minimal over just a few minutes, but grows into a substantial risk over several hours. As a result, tachycardia is a contraindication only for the longer-acting of the two medications: albuterol.
| Epinephrine | Albuterol | |
| Indication | Systemic allergic reaction (anaphylaxis) | Asthma attack or difficulty breathing with wheezing |
| Action | Constricts veins and dilates bronchi | Dilates bronchi |
| Contraindications | Chest pain of cardiac origin, hypothermia, high blood pressure | Chest pain of cardiac origin, albuterol allergy, high heart rate |
| Side effects | Anxiety, restlessness, high heart rate, high blood pressure | Anxiety, restlessness, high heart rate, high blood pressure |
| Dose and route | Intramuscular, 0.3 mg adults/0.15 mg children | Inhalation, 1-2 puffs of MDI |
You can see other EMS-related posts here.