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EPINEPHRINE AS A TREATMENT FOR ANAPHYLAXIS

Category: Medical

Topic: Immunology

Level: EMT

Next Unit: Pediatric Dosages of Epinephrine

17 minute read

Epinephrine as Treatment for Anaphylaxis

Anaphylaxis is the presence of a massive out of proportion allergic response to an antigen, it occurs in certain individuals and tends to recur with repeated exposure to the given antigen. Anaphylaxis is defined as "the development of allergic symptoms in more than one bodily system up to one hour after exposure to an antigen." The presence of difficulty breathing and/or hypotension is not required for an anaphylaxis diagnosis, though these findings are common.

Prompt assessment and treatment are critical in anaphylaxis, as respiratory or cardiac arrest and death can occur within minutes. Also, it is most responsive to treatment in its early phases: for these reasons Delayed epinephrine injection is strongly associated with fatalities.

 

Indications and Contraindications

Indications for epinephrine include severe allergic reaction defined as the presence of allergic symptoms in two or more bodily systems. 

Contraindications to epinephrine are rarely absolute, the only absolute contraindications are expired medication, discolored medication, or in the case of EMR providers if the medication is not actually prescribed to the patient.

Caution should be used in patients that are known to have conditions such as diabetes, hyperthyroidism, or known cardiac disease. This is because it raises the heart rate and can lead to myocardial infarction in patients that have underlying cardiac disease. 

 

Action and Benefits of Epinephrine

The action of epinephrine is centered around its activation of the sympathetic nervous system, it acts on multiple receptors in this system.

The Alpha 1 Receptors cause vasoconstriction which decreases any edema (swelling) in the airways. It also causes blood vessels to clamp down, increasing blood pressure. 

The Beta 2 Receptors cause bronchodilation helping to relieve any asthma-like swelling of the small airways in the lungs, it also promotes an increased heart rate to raise the blood pressure. 

The other beneficial effects of epinephrine are related to its ability to directly decrease the activity of certain immune system cells that release large amounts of chemicals that trigger the overactive allergic response. 

 

IM is Preferred Route

In anaphylaxis, epinephrine should be given IM preferentially, which allows for faster absorption than sub-Q and minimizes cardiac side effects.

Autoinjection Systems: The auto-injection systems are provided by a doctor’s order, must belong to the patient and must not be expired.

Prepare the injection site with alcohol and remove the needle cover. To administer, push the needle firmly into the lateral thigh and hold for ten seconds to allow the drug to be fully injected. Monitor the patient response, and dispose of the autoinjector in a sharps container.

Advanced providers, with proper training and if protocols allow, are more frequently drawing up and administering epinephrine through manual hypodermic needles and syringes, due to increasing prices and thus unavailability of epinephrine auto-injectors. Intramuscular and subcutaneous are the preferred routes of administration and dosages are generally 0.3 mg of epinephrine 1:1,000 for adults. Administer according to protocol.

IM Dosing

  • 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.

 

Side Effects

Side effects include

  • increased pulse rate and blood pressure,
  • anxiety, and
  • cardiac arrhythmias.

Dosing mistakes: Medication errors have occurred due to confusion with epinephrine products expressed as ratio strengths (e.g., 1:1000 vs 1:10,000).

Epinephrine 1:1000 = 1 mg/mL and is most commonly used IM.

Also, topical epinephrine is 1:1000. Vials of topical and injectable epinephrine look similar. Epinephrine 1:10,000 = 0.1 mg/mL and is used IV.

 

Adverse Reactions

Cardiovascular:

The most common "adverse reactions" to epinephrine are tachycardia and palpitations, these are directly related to its beta stimulating effect on the heart, these side effects are transient and will naturally resolve as the epinephrine wears off. If epinephrine is used in a patient that has arterial disease it is possible to see side effects such as stroke, myocardial infarction, or ischemia elsewhere in the body. The risk of these side effects is never a reason to withhold epinephrine from a patient in obvious anaphylaxis! 

In rare cases epinephrine can cause cardiac arrhythmias in otherwise healthy patients, SVT and V-Tach are the most commonly seen though -Fib has been reported. Often these arrhythmias self resolve, but they are one of the reasons patients that have been, or will be, given epinephrine should be on cardiac monitors. 

CNS:

Epinephrine is one of the primary hormones involved in the "fight or flight" reflex, patients who have been given epinephrine may experience symptoms such as anxiety, fear, disorientation, excitability, and impaired memory. The effects on the peripheral sympathetic nerve can also lead to diaphoresis and flushed skin. 

Some of the more alarming CNS side effects are those that may be the result of a potential stroke such as one-sided weakness, paresthesias, drowsiness, and mental status change. 

GI:

Nausea and vomiting may be seen as a reaction to the stimulation of the sympathetic "fight or flight" reflex. 

Respiratory:

Ironically epinephrine administration can cause a sensation fo shortness of breath, this does not mean it is not working to reduce airway swelling but rather that the patient may be experiencing the sympathetic fight or flight reflex mentioned above. Ensure that breath sounds are clear and breathing is not stridulous or labored to ensure that the epinephrine is having the desired effect. 

 

Preferred Injection Site

The preferred injection site is the anterolateral aspect of the thigh.

Do not inject into the buttock: not only is it not always effective in treating anaphylaxis but has been associated with Clostridial infections (gas gangrene).

Serious skin and soft tissue infections, including necrotizing fasciitis and myonecrosis caused by Clostridia (gas gangrene), have been reported rarely at the injection site.

Cleansing skin with alcohol may reduce bacteria at the injection site, but alcohol cleansing does not kill Clostridium spores. Do not administer repeated injections at the same site (tissue necrosis may occur). Monitor for signs/symptoms of injection-site infection.

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