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Immunology – Anaphylaxis
Whiteboard Animation Transcript
with George Porfiris, MD
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Anaphylaxis is a rapid-onset life-threatening allergic reaction. Because of its high risk of mortality, it is a diagnosis that you cannot afford to miss.

Think of this condition in a patient who presents with an urticarial rash and one other system affected – a rule I like to call “Skin + 1”.

Anaphylaxis is most commonly caused by one of the following three triggers:

Foods such nuts, shellfish, and eggs and milk especially in kids;
Medications including antibiotics like penicillin and sulfa drugs, aspirin, and IV contrast used in diagnostic imaging procedure; and
Environmental: things like insect stings from bees and wasps, and latex.

Prior exposure to one of these triggers sensitizes individuals to release massive amounts of histamine, leukotrienes and other inflammatory mediators from mast cells in their blood leading to a spectrum of symptoms.

If only the skin is involved, it is not anaphylaxis, but called urticaria, as anaphylaxis requires 2 organ systems to be involved.

Urticaria presents with an intensely itchy hive like rash on the trunk, limbs, and face. This is not a life threatening condition and can be treated with antihistamines, such as Benadryl, for a few days.

On the other hand, if the skin plus one other system or “Skin + 1” is involved then, the criteria for anaphylaxis has been met, and this is a medical emergency that you just cannot afford to miss. The other systems (or the “+1”) that are commonly involved include:

Respiratory: and can present with upper airway involvement with stridor, tongue, lip, or neck swelling or lower airway presenting with wheezes, cough and shortness of breath. Airway obstruction is the number one cause of death from anaphylaxis.
Cardiovascular: presenting with hypotension or frank shock and complete circulatory collapse.
Gastrointestinal: presenting with nausea, vomiting, diarrhea, and abdominal cramps due to the massive histamine release.
The treatment of anaphylaxis must be started as soon as the condition is suspected. Time is of the essence.

The most important drug to administer is EPINEPHRINE. This is what will save lives. Do not hesitate to give it. It starts working within seconds of being given. The dose is epinephrine 0.3mg-0.5mg in a 1/1000 concentration IM, usually given in the thigh. The pediatric dose is 0.01mg/kg.
Epinephrine can be repeated every 5 minutes if necessary.

Prompt recognition, early intervention, and preventing further episodes with allergy testing, allergy avoidance, and the Epi-Pen use are all key for managing this life threatening condition.

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