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Common anaphylaxis exam questions for medical finals, OSCEs and MRCP PACES

 

Question 1: Recognising anaphylaxis

What are the key signs and symptoms of anaphylaxis?

  • Acute onset
  • Airway and breathing
    • Dyspnoea, respiratory distress, wheeze, stridor
    • Cyanosis
  • Circulation
    • Tachycardia, hypotension
  • Skin
    • Urticaria, angioedema

What skin changes can occur as part of anaphylaxis?

  • Urticaria and/or angioedema (systemic, usually more notable around the face) occurs in 80%

 

Question 2: Pathophysiology of anaphylaxis

What is the pathophysiology of an anaphylactic reaction?

There is a sensitisation phase and an effector phase that give rise to the symptoms:

  • Sensitisation phase
    • Immune system encounters allergen and makes immunoglobulin E (IgE) against it
    • No clinical features occur
  • Effector phase
    • Allergen cross-links IgE on surface of mast cells
    • Causes widespread degranulation and release of histamine which mediates inflammatory bronchospasm, vasodilatation, increased capillary permeability, and tissue oedema

 

Question 3: Adrenaline (epinephrine) in anaphylaxis

What dose and route of adrenaline would you give to an adult patient with anaphylaxis?

  • 500 micrograms (0.5 ml of 1:1,000) IM

What dose and route of adrenaline would you give to a child aged 15 years with anaphylaxis?

  • 500 micrograms (0.5 ml of 1:1,000) IM
    • Same as the adult dose until age 12

What dose and route of adrenaline would you give to a child aged 10 years with anaphylaxis?

  • 300 micrograms (0.3 ml of 1:1,000) IM
    • This is the dose for a child 6-12 years

What dose and route of adrenaline would you give to a child aged 4 years with anaphylaxis?

  • 150 micrograms (0.15 ml of 1:1,000)
    • This is the dose for a child of 5 years and under

 

Question 4: Other drugs in anaphylaxis

What doses and routes of chlorphenamine and hydrocortisone would you give to an adult with anaphylaxis?

  • Chlorphenamine (piriton) 10mg IM or IV
  • Hydrocortisone 200mg IM or IV

Question 5: Confirmation of anaphylaxis

What blood test can help in the retrospective diagnosis of anaphylaxis?

  • Mast cell tryptase
    • Take three samples taken as soon as possible, after 1-2 hours and after 24 hours
    • Useful in making a retrospective diagnosis but the absence of a rise does not exclude anaphylaxis

Click here to download free teaching notes on anaphylaxis: Emergency – Anaphylaxis

Perfect exam revision for medical students, finals, OSCEs and MRCP PACES