Anaphalaxis

Question 1

What is the pathophysiology of anaphalaxis?

Answer 1

An exagerated immune response that is classically IgE mediated

• caused by repeated bouts of sensitization and reexposure
• mast cells degranulate causing histamine release

Question 2

What are the criteria for the diagnosis of anaphylaxis?

Answer 2

if 1 of the 3 is present, then anaphylaxis is likely

1) acute onset with skin or mucosal involvement and at least one of
- respiratory compromise
- hypotension or symptoms of end organ dysfunction (syncope, incontinence)

2) two or more of the following that occur rapidly after exposure to a likely allergen for that patient
- skin and or mucosal involvement
- respiratory compromise
- reduced BP or symptoms of end organ dysfunction
- gastrointestinal symptoms

3) reduced BP after exposure to a known allergen for that patient
- adults : sbp< 90mmHg or greater than 30 percent decrease from baseline

Question 3

What is the management of anaphylaxis?

Answer 3

1) Remove causative agent and ABC’s
2) Epinephrine
- adult 0.3-0.5ml of 1:1000 solution IM epinephrine
- child 0.01 ml/kg up to 0.4 ml/ dose of 1:1000 epinephrine

3) diphenhydramine (benadryl) 50mg IM or IV q4h
4) dimenhydrinate (gravol) 50mg IM or IV Q4
4) methylprednisone 50-100mg IV (dose dependant on severity)
5) salbutamol via nebulizer if bronchospasm
6) H1 antagonist (cetirizine 10mg PO OD)
7) H2 antagonist (ranitidine 150mg PO OD)

Question 4

What is the difference between anyphylaxis and and anaphylactoid reaction?

Answer 4

anyphylactoid reactions are those that produce the same clinical picture as anaphylaxis but
1)are not IgE mediated, occur through a direct nonimmune-mediated release of mediators from mast cells and/or basophils or result from direct complement activation