Wilderness Emergency Medical Services Institute

Anaphylaxis and the Epinephrine Inhaler:
Are We Missing A Bet?

by

Jay Wiseman
First Responder Instructor

Editor's Note:
This is the first article we have received from a person who is trained at the First Responder level. We hope it will be the first of many.
Bernie Roche
WEMSI Web Site Administrator

When I teach one of my basic first aid classes to a group of ordinary citizens, I like to explain to them that most of prehospital emergency medicine is something of an exercise in passing the buck.  As citizens, their task is to keep the patient alive until the first responders arrive on the scene.  The task of the first responders is to keep the patient alive until the ambulance crew gets there.  The task of the ambulance crew is to keep the patient alive until they reach the hospital, and so forth.

So, as far as average citizens in the typical urban or suburban area (where EMS assistance is readily available) are concerned, the obvious question becomes:  what conditions will kill the patient in the five to fifteen minutes it will take the first responders to arrive?  Clearly, priority should be given to intervening in those particular situations. In my experience, there are five such conditions:

1. an obstructed airway,
2. respiratory arrest,
3. cardiac arrest (by far the most common),
4. very severe bleeding, and
5. a very severe allergic reaction.

A severe allergic reaction (anaphylaxis) is a chemical emergency, and it demands chemical intervention.  In the case of anaphylaxis, the patient may develop some or all of the following conditions:

1. vasodilation leading to hypotension,
2. bronchospasm leading to respiratory distress and impaired ventilation,
3. laryngeal edema which further impairs respiration, and may even prevent it entirely.

One question is how best to administer this drug.  The traditional means of giving epinephrine is by injection -- usually either subcutaneously (SC) or intravenously (IV).  Indeed, in the United States, patients who are prone to severe allergic reactions are often advised to carry injectable epinephrine and are given a prescription for such an injector -- typically called either an Epipen or an Anakit.

However, there is good evidence that giving the drug by inhalation can also be effective, and may be particularly effective in treating the laryngeal edema (1), (2).  Indeed, one author of textbooks for EMT's and paramedics recommends that epinephrine be given by the inhaler route by EMT's when they are treating a patient suffering from a severe allergic reaction (3).

There is fairly good scientific evidence to back up this recommendation. Studies show that epinephrine actually has a quicker onset when given by inhalation (three to five minutes) as opposed to when given by subcutaneous or intramuscular injection (five to ten minutes), with comparable peak effects (20 minutes for all three routes), and similar durations (one to three hours for epinephrine given by inhalation versus one to four hours for epinephrine given by SC or IM injection). (4)

In the United States, the self-injector continues to be the most commonly recommended device for use by allergic patients in the event of an emergency, but in Europe the epinephrine inhaler has a broader following. Indeed, researchers there have found that, because the inhaler lacks a needle, patients are less reluctant to use it (the frequency and severity of "needle-phobia" on the part of ordinary citizens may be severely under-appreciated by many medical personnel), that epinephrine given by inhaler has a more immediate effect on the laryngeal edema and the respiratory distress associated with anaphylaxis than does epinephrine given by any form of injection, and that an inhaler can have up to three times the shelf life of a self-injector.  Let me add that in the United States an epinephrine inhaler is available without prescription and at about one-third the cost of a self-injector (5), (6).

So a good case can be made for the epinephrine inhaler, but it is not without its drawbacks.  Most importantly, it takes about ten to twenty correctly administered "puffs" to achieve a full, therapeutic dose of epinephrine -- although the patient often starts to benefit from a lesser dose -- as opposed to a single injection of the drug. (It should be pointed out that a standard epinephrine inhaler contains approximately 300 "puffs" worth of the drug.)  Also, epinephrine given by injection has reportedly been more effective in treating the hypotension associated with anaphylaxis.  Furthermore, it is relatively easy to give epinephrine by injection to an unconscious patient, whereas giving it by inhaler would be very difficult, if not impossible using the techniques currently available.  (This could be a research opportunity.)

Patients who know that they are severely allergic to stings, various foods, and/or medications should consult their physician regarding the advisability of carrying an epinephrine self-injector, and should also ask about being referred to an allergist for desensitization therapy.  An epinephrine inhaler might make a good addition to, but not a replacement for, the self-injector in such high-risk patients.

Still, given its low cost, long shelf life, readily availability, high rate of patient compliance, and proven effectiveness, the epinephrine inhaler should receive greater usage than it currently does.  It would make an excellent addition to a first aid kit.

(1)  "Hypodermic epinephrine spray and uvular angioedema revisited" by Peltz, et al.  Journal of Allergy and Clinical Immunology, Volume 97, number two, pages 717-718.

(2) " Laryngeal odema following anaphylactic shock" by McConachie. British Journal of Hospital Medicine, 1992, Volume 47, Number 3, page 201.

(3)  "Emergency Medical Treatment" (third edition) 1991 by Caroline. Pub. by Little, Brown.

(4)  "Nurses Drug Handbook 1995" by Hodgson, Kizior, and Kingdon, published by Saunders.

(5)  "Emergency treatment of allergic reactions to Hymenoptera stings" by Muller, et al.  Clinical and Experimental Allergy, 1991, Volume 21, pages 281 [note:  this is a key article regarding the inhalation versus injection modalities]

(6)  "Route of administration of adrenaline for the treatment of anaphylactic reactions to bee or wasp stings" [letter, comment] by Ewan, et al.  Clinical and Experimental Allergy, 1991, Volume 21, pages 753-756.  [note:  this somewhat critical letter, and the reply by the original authors, constitute, along with reference #5, the key writings on this issue]

Keith Conover, Wemsi's medical director, writes:
(edited for brevity)

Dear Jay:

It's an interesting article, and worthy of posting for comments.

The content is fine as is, but I would make one addition.

There has been a move afoot to remove epi inhalers from the market, or at least require a prescription for them - it is suspected that overuse of these inhalers for asthma may be at least partially responsible for the increase in asthma deaths recently.  Remember that albuterol and related compounds tend to have maximal effects on the lungs and minimal on the heart, based on their pharmacology.  This isn't true for epinephrine, which has very strong effects on the heart - and may lead to v. tach or v. fib arrests.

I don't have the citations handy, but a medline search should turn them up.

But with a caveat that epi inhalers are not to be used for asthma unless it looks like the patient is about to arrest, or is at least critically ill - the article looks great, and it's a good idea.  I wouldn't mind seeing lots of WFRs carrying epi inhalers.  It's a lot better use than for chronic treatment of asthma, certainly.

Take care.

Keith Conover, M.D., FACEP

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