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Friday, August 10, 2012

"Anaphylaxis Knowledge Among Paramedics"

As with any area in EMS, anaphylaxis generates a good amount of discussion. For example, people like to discuss the best way to give epinephrine intravenously. Other people can get really engaged in how glucagon might work in anaphylaxis (if it works). These conversations can get pretty involved in complicated biochemistry, or in personal experience, or even both.

Such discussions are interesting, but I get concerned that the central message about anaphylaxis treatment gets muddled and confused. Unfortunately, a recent study confirms my suspicions. 

The Bottom Line: How to treat anaphylaxis
Before reviewing the new study, it's worth emphasizing the current standard of care for the treatment of anaphylaxis:
  • Epinephrine, 0.01 mg/kg (max 0.5 mg),
  • delivered intramuscularly,
  • in the lateral thigh. 
Not subcutaneous, not in the deltoid, and 0.3 mg is not the upper limit.

The Study
Okay, with  that established, I want to review a recent study that suggests that paramedics might often be confused about this issue. Why they're confused will be discussed below, but it comes down to, at least in part, education and medical control, I believe.

The study, "Anaphylaxis Knowledge among Paramedics", was performed in Missouri, and has a MD/paramedic as lead author! 



I don't usually get excited about studies that use a survey, and even less so when it's an online survey. A survey design can often just be a lazy way to get published.

" I'm in print! Things are going to start happening to me now." Me, in 2006.
 The authors really did their homework on the design though, and they ended up getting responses from about 5% of all nationally registry paramedics. Odds-wise, you work with someone who answered the survey.

They gave a few scenarios, and then asked both closed- and open-ended questions about anaphylaxis diagnosis and treatment. For example:


They also posed an atypical anaphylaxis scenario that was, at least for me, really hard to diagnose.

The results
Briefly, they found that most paramedics:
  • Didn't pick epinephrine as the initial therapy (only 46% did so)
  • Picked the wrong route for epi (just 39% chose IM)
  • Picked the wrong location (a mere 12% described the thigh as the best site)
  • Believe there are contraindications for epi in anaphylaxis (not according to the experts)
An uncharitable way to interpret the results is that many paramedics don't know how to treat anaphylaxis, and that they don't understand the lack of contraindication.

First, though, what is the best way to treat anaphylaxis?
Drug, Dose, Route
First off, repetition is the soul of learning:
  • Epinephrine, 0.01 mg/kg (max 0.5 mg),
  • delivered intramuscularly,
  • in the lateral thigh. 
 Here's a cartoon that explains for the visual learners out there:

Recent World Health Organization (WHO) guidelines - download PDF!
The experts are all in agreement here, from EMS organizations (The use of epinephrine for out-of-hospital treatment of anaphylaxis: resource document for the National Association of EMS Physicians position statement.), to the allergists (Second symposium on the definition and management of anaphylaxis), to the World Health Organization (WHO), as shown above. 

What about diphenhydramine, steroids, glucagon, and all the other drugs? Well, they're fine to give, but they are not useful in acute management of anaphylaxis. In fact, one study, where they were trying to desensitize people with bee-sting allergies, only used epinephrine for the anaphylactic reactions they occasionally caused.

No Benadryl here.

Okay, so we're clear on how and why to give epi. Why did the medics think there were times when a patient in anaphylactic shock should not get epi?

Contraindications: A Review
About 36% of the medics listed contraindications to giving epinephrine for anaphylactic shock, which is concerning, since there are no absolute contraindication if the patient is having true anaphylactic shock. Here's a breakdown of the reasons they gave.


The most frequent concerns revolved around giving epinephrine to a patient with heart disease (or an older patient, and thus at risk of heart disease), and causing more problems. The recent WHO guidelines are reassuring, however, and I quote [my emphasis]:
"Although caution is necessary and dosing errors need to be avoided, epinephrine is not contraindicated in the treatment of anaphylaxis in patients with known or suspected cardiovascular disease, or in middle-aged or elderly patients without any history of coronary artery disease who are at in- creased risk of ACS only because of their age."
In fact, there is evidence to suggest that epinephrine protects the heart against ischemia, through dilation of coronary arteries. In fact, anaphylaxis often causes cardiac problems, such as ischemia, bradycardia, and sometimes MIs, and a cardiac arrest may result from incomplete treatment. 

Check out these examples:

Acute coronary syndrome triggered by honeybee sting: a case report.

ST-segment elevation myocardial infarction following a hymenoptera (bee) sting.

Acute anterior myocardial infarction after multiple bee stings.

Insect sting anaphylaxis; prospective evaluation of treatment with intravenous adrenaline and volume resuscitation.


I'm not sure about answer #2, ("allergy to epinephrine"), but let's just ignore that and move on...

Since a shock state may cause a reflex tachycardia, reason #3 seems more like an indication to give epi. Likewise, shock and hypotension (answer #6) pretty much define anaphylactic shock, so it's unclear how that would be a contraindication. If a patient with possible anaphylaxis were hypertensive, (#5), on the other hand, you could reasonably debate whether anaphylactic shock was a concern!

Why did paramedics do so poorly on the survey?
The authors discuss this at some length, but I'm inclined to blame, well, us. The medical directors, the educators, the state officials - the people who set the protocols and policies, as well as the curricula.

The change in the expert recommendations for epi administration happened years ago, but in many regions the protocols have not reflected this.

In fact, in some places, it is the EMT-Basics (who are limited to using the Epi-Pen) who are practicing at the current standard of care, since they have no option to give epi any other way.

Not a medic, but practicing the standard of care! (about.com)

Paramedics, however, with their expanded skill set, are able (and often required) to give it the ol' fashioned way. The not-quite-as-effective way. And until we change the protocols, medics are going to answer test questions based on what we require them to do.

The Bottom Line, part 2
While everyone likes to talk about the latest updates in ACLS, cool new devices for intubation, or new drugs or methods for cardiac arrest, EMS has not been as quick to pick up on the new, evidence-based treatment of anaphylactic shock.

And what is that, you ask? I'm so glad you asked!
  • Epinephrine, 0.01 mg/kg (max 0.5 mg),
  • delivered intramuscularly,
  • in the lateral thigh.

 

4 comments:

  1. Our previous protocols had this obnoxious requirement:

    "Contact Medical Control prior to administering epinephrine in patients who are >50 years of age, have a history of cardiac disease, or if the patient's heart rate is >150. Epinephrine may precipitate cardiac ischemia. These patients should receive a 12 lead ECG."

    Now it has been replaced by:

    "Patients who are ≥ 50 years of age, have a history of cardiac disease, take Beta-Blockers / Digoxin or patient's who have heart rates ≥ 150 give one-half the dose of epinephrine (0.15 – 0.25 mg of 1:1000.) Epinephrine may precipitate cardiac ischemia. These patients should receive a 12 lead ECG at some point in their care, but this should NOT delay administration of epinephrine."

    I'm not sure why B-blocker/Dig patients should receive less epinephrine and it is almost counter-intuitive...However, I am glad we don't have to call for orders just because a patient is 50 years old.

    ReplyDelete
  2. Interesting revision. Wonder where they came up with the half-dose epi?

    ReplyDelete
    Replies
    1. One guess is this is a compromise between the progressive systems and the regressive systems in the State.

      Anecdotal evidence seems to support this theory. The local history for one of the counties I work in claims they once had a medical director who believed EMS should not administer epinephrine for anaphylaxis ever, as paramedics were not adequately trained to know how/when.

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    2. reductio ad absurdum:

      http://www.ems1.com/ems-oddities/articles/1261603-FDNY-to-test-yellow-cab-EMS-model-to-shorten-response-times/

      Delete