Anaphylaxis

Question 1

What is anaphylaxis?

Answer 1

acute life-threatening multisystem syndrome caused by sudden release of mast cell + basophil-derived mediators into the circulation

Question 2

What are the 2 types of anaphylaxis?

Answer 2

Immunogenic: IgE-mediated or immune complex/complement-mediated
Non-Immunogenic: mast cell or basophil degranulation WITHOUT involvement of antibodies (e.g. reactions to vancomycin, codeine, ACEi’s)

Question 3

List 4 common allergens

Answer 3

Drugs (e.g. penicillin)
Latex
Peanuts
Shellfish

Question 4

Describe the epidemiology of anaphylaxis

Answer 4

Common

Question 5

Describe the Pathophysiology of anaphylaxis

Answer 5

Inflammatory mediators e.g. histamine are released leading to bronchospasm, increased capillary permeability + reduced vascular tone
This leads to tissue oedema

Question 6

List 5 symptoms of anaphylaxis

Answer 6

Wheeze  
SOB + a sense of choking  
Swelling of lips + face  
Pruritus 
Rash

Question 7

List 9 signs of anaphylaxis

Answer 7

Tachypnoea  
Wheeze  
Cyanosis  
Swollen upper airways + eyes  
Rhinitis  
Conjunctival infection  
Urticarial rash  
Hypotension  
Tachycardia

Question 8

What investigations are made in acute presentation of anaphylaxis?

Answer 8

CLINICAL dx

Serum tryptase, histamine or urinary metabolites of histamine may help support clinical dx

Question 9

How do you treat anaphylaxis?

Answer 9

ABCDE 
High flow oxygen  
IM Adrenaline  
Chlorpheniramine (antihistamine IV) 
Hydrocortisone  (steroid)
IV crystalloid to maintain BP
Treat bronchospasm with salbutamol/ ipratropium
Monitor pulse oximetry, ECG + BP

Question 10

What are the possible complications of anaphylaxis?

Answer 10

Respiratory failure
SHOCK
Organ damage can result from shock

Question 11

What is the prognosis for patients with anaphylaxis?

Answer 11

Good with prompt treatment

Question 12

What investigations are made following an anaphylaxis attack?

Answer 12

Allergen skin testing: identifies allergen

IgE immunoassays: identifies food-specific IgE in the serum

Question 13

When does anaphylaxis arise due to repeated administration of blood products?

Answer 13

In a patient with selective IgA deficiency (due to formation of anti-IgA antibodies)

Question 14

What may be present in the PMH of a patient with anaphylaxis ?

Answer 14

other hypersensitivity reactions (e.g. asthma, allergic rhinitis)

Question 15

How does IM adrenaline help treat anaphylaxis?

Answer 15

Causes vasoconstriction: raises BP
Increases contractility + HR
Relaxes smooth muscles that line bronchi