Anaphylaxis

Question 1

Explain the pathophysiology of anaphylaxis?

Answer 1

The body reacts to a non harmful allergen usually via IgE.

This causes activation of mast cells and basophils ignites a cascade that results in the release and production of severe inflammatory and vasoactive substances.

Question 2

What are the common features associated with anaphylaxis?

Answer 2

Facial swelling (angioedema) causing upper airway obstruction
Hives
Drop in BP
Itchiness

Question 3

What are the common allergens in children that cause anaphylaxis and what are the risk factors for developing anaphylaxis?

Answer 3

Allergens:
Peanuts
Nuts
Eggs
Shellfish
Medications (abx, NSAIDs, opioids, anaesthetics)

Risk factors:

• Asthma/hayfever aka atopy
• FH of anaphylaxis and allergy

Question 4

What is the management in anaphylaxis?

Answer 4

ABCDE

Call for help!

Adrenaline (epinephrine) 1:1000 given IM

• 500 micrograms if over 12
• 300 micrograms 6-12
• 150 micrograms under 6

IM/slow IV hydrocortisone and chlorphenamine.

Fluid resuscitation is also important.

Steroids can be used to prevent a second late stage reaction.

Question 5

What should the patient be sent home with?

Answer 5

Epipen for on the go IM adrenaline.
Antihistamines for milder reactions.

Information regarding allergen avoidance.

Question 6

What investigations should be done in someone that has had anaphylaxis?

Answer 6

Cutaneous antigen testing can be used after recovery to try to identify the inciting antigen.