September 19, 2019
Immunology – Anaphylaxis: By George Porfiris M.D.

Immunology – Anaphylaxis: By George Porfiris M.D.


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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