Anaphylaxis Flashcards
What is anaphylaxis?
A severe, life-threatening, generalised or systemic hypersensitivity reaction
Is anaphylaxis common?
No, it’s actually rare
Why is anaphylaxis often fatal?
Rapid onset of symptoms and laryngeal oedema
In what age group do most cases of anaphylaxis occur?
Under 5’s
Why do most cases of anaphylaxis occur in under 5’s?
This is when food allergy is most prevalent
When do most cases of fatal anaphylaxis occur?
In adolescents
What is the most common cause of fatal anaphylaxis?
Nut allergy
What is responsible for the allergic reaction in anaphylaxis?
Release of inflammatory mediators and cytokines from mast cells and basophils
What are the two mechanisms that can underly anaphylaxis?
- Immunological mechanism
- Non-immunological mechanism
What is the initial step in the immunological mechanism of anaphylaxis?
IgE binds to antigens forming a complex that activates receptors on mast cells and basophils
What happens as a result of activation of mast cell and basophil receptors?
There is a release of inflammatory mediators
Give an example of an inflammatory mediator involved in anaphylaxis
Histamine
What are the effects of the inflammatory mediators released by mast cells and basophils?
- Increased contraction of bronchial smooth muscle
- Vasodilation
- Blood vessel leakage
- Heart muscle depression
What does the non-immunological mechanism involve?
Substances directly causing degranulation of mast cells and basophils
What percentage of anaphylaxis in children is caused by food allergy?
85%
What are some other causes of anaphylaxis?
- Insect stings
- Drugs
- Latex
- Exercise
- Inhalant allergens
Is a cause of anaphylaxis always identified?
No
What are the risk factors for developing anaphylaxis?
- Asthma
- Other atopic diseases
- Higher socioeconomic status
What can be used to assess the symptoms of anaphylaxis?
ABCDE assessment
What is seen on Airway assessment in anaphylaxis?
- Swelling
- Hoarseness
- Stridor
What is seen on Breathing assessment in anaphylaxis?
- Tachypnoea
- Wheeze
- Cyanosis
- SpO2 <92%
What is seen on Cardiovascular assessment in anaphylaxis?
- Pale
- Clammy
- Hypotension
- Drowsiness
- Coma
What is seen on assessment of Everything Else in anaphylaxis?
Urticaria/angioedema (not always)
Should anaphylaxis be acutely investigated?
No - its a clinical diagnosis
What investigations may be needed in the long-term management of anaphylaxis?
Allergy testing
What are the differentials for anaphylaxis?
- Allergic reaction
- Angioedema
- Asthma exacerbation
How should anaphylaxis be immediately managed?
- Adrenaline 1:1000 IM
- Changes in posture
In what situations may posture changes help?
- Difficulty breathing
- Hypotension
- Unconscious
What position may help with difficulty breathing?
Sat up
What position may help with hypotension?
Supine with legs in the air
What position may help with unconsciousness?
Recovery position
How should anaphylaxis be further managed?
- Establish airway
- High flow oxygen
- IV fluids (20ml/kg crystalloids)
- Chlorpheniramine (IM or slow IV
- Hydrocortisone (IM or slow IV)
- Salbutamol if wheeze
How should a patient that has experienced anaphylaxis be monitored?
- Pulse oximetry
- ECG
- BP
What should be considered when forming a long-term management plan for anaphylaxis?
- Acute management strategies
- Trigger avoidance training
How should a long-term management plan be given?
As a written plan with instructions and adrenaline auto-injectors
What may be effective in preventing future anaphylaxis in some cases?
Allergen immunotherapy
What are the potential complications of anaphylaxis?
- Death
What can cause death in anaphylaxis?
Respiratory or circulatory failure
