Anaphylaxis

Question 1

Definition

Answer 1

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

Question 2

Aetiology/Risk Factors

Answer 2

· Immunogenic - IgE-mediated or immune complex/complement-mediated

· Non-Immunogenic - mast cell or basophil degranulation WITHOUT the involvement of antibodies (e.g. reactions caused by vancomycin, codeine, ACE inhibitors)

Question 3

Epidemiology

Answer 3

Common

Question 4

Presenting Symptoms

Answer 4

· Wheeze
· Shortness of breath and a sense of choking
· Swelling of lips and face
· Pruritus
· Rash
· NOTE: patients may have a history of other hypersensitivity reactions (e.g. asthma, allergic rhinitis)

Question 5

Signs on Physical Examination

Answer 5

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

Question 6

Investigations

Answer 6

At point of CLINICAL diagnosis

· Serum tryptase, histamine levels or urinary metabolites of histamine may help support the clinical diagnosis

Following an attack

· Allergen skin testing - identifies allergen
· IgE immunoassays - identifies food-specific IgE in the serum

Question 7

Management Plan

Answer 7

· ABCDE
· High flow oxygen
· IM Adrenaline
· Chlorpheniramine (antihistamine)
· Hydrocortisone
· If continued respiratory deterioration, may require bronchodilator therapy
· Monitor pulse oximetry, ECG and BP

Question 8

Possible Complications

Answer 8

· SHOCK

· Organ damage can result from shock

Question 9

Prognosis

Answer 9

Good with prompt treatment

Question 10

Pathophysiology

Answer 10

• Inflammatory mediators such as histamine are released leading to bronchospasm, increased capillary permeability and reduce vascular tone
• This leads to tissue oedema

Question 11

Common allergens

Answer 11

• Drugs (e.g. penicillin)
• Latex
• Peanuts
• Shellfish
• NOTE: anaphylaxis can be caused by the repeat administration of blood products in a patient with selective IgA deficiency (due to the formation of anti-IgA antibodies)