Anaphylaxis Flashcards
Define anaphylaxis
Severe, life-threatening, generalised or systemic hypersensitivity reaction.
What is the relevant epidemiology of anaphylaxis?
Peak: 20-30yrs
20 cases per 100,000 person-years
What is the common aetiology of anaphylaxis?
Triggered by allergens - normally harmless substances that trigger an exaggerated immune response in susceptible individuals.
Foods - peanuts, eggs, fish
Insect venom - bees,
Medications - penicillins, NSAIDs, chemo
Latex -
Idiopathic - remains unknown
What is the key pathophysiology of anaphylaxis?
Is a type 1 hypersensitivity reaction - characterised by IgE.
Sensitization - exposure, APCs, naive to Th2, IL-4/12, IgE from B cells, IgE bind to FCreceptors on mast and basophils - primed
Effector - 2nd exposure, antigen cross-links IgE, triggers inflammatory mediator release
Prefromed mediators - vasodilation, vascular permeability and smooth muscle contraction, mucus secretion
Late phase response from newly formed mediators - amplifying and prolonging the reaction.
What are the non-IgE mediated anaphylaxis?
Complement activation
Direct mast cell activation - radiocontrast media or opioids
IgG or IgA mediated immune complex formation
What does the RESUS council define anaphylaxis as?
Sudden onset and rapid progression of symptoms with and/or A/B/C
Airwar - swelling or throat and tongue - hoarse voice and stridor
Breathing - resp wheeze, dyspnoes
Circulation - hypotensive, tachycardia
What are the key signs/symptoms of anaphylaxis?
Airwary - swelling or throat and tongue - hoarse voice and stridor
Breathing - resp wheeze, dyspnoes
Circulation - hypotensive, tachycardia, angioedema
Disability - confusion
Generalised pruritus
Widespread eryhtematous or urticarial rash
Periorbital oedema
These are sudden and severe in onset.
What is the key medication to be delivered in anaphylaxis?
IM adrenaline - typically middle third of the thigh
Can be repeated every 5 minutes if needed
What are the recommended doses for adrenaline?
Typically 0.1ml per Kg
<6months = 100-150 micrograms
6m to 6yrs - 150 micrograms
6-12yrs - 300 micrograms
Adults and child >12yrs - 500 micrograms
What is meant by refractory anaphylaxis?
Respiratory and/or cardiovascular problems persist despire 2 doses of IM adrenaline
What is the treatment for IM adrenaline refractory anaphylaxis?
IV fluids for shock
Expert help for consideration of IV adrenaline infusion
What is the typical management following stabilisation of anaphylaxis?
- Non-sedating anti-histamins if skin symptoms
- serum tryptase -> confirm anaphylaxis if raised (for up to 12hrs after)
- Referall to specialist allergy clinic
- Adrenaline injector prescribed - 2 auto-injectors and training on how to use it
- Risk stratified approach to discharge - cuations of biphasic reactions.
Who can recieve a fast track discharge after anaphylaxis?
After 2hrs of resolution
Good response to single dose of adrenaline
Complete symptoms resolution
Given adrenaline auto-injector and passed training
Adequate supervision following discharge
Who might recieve a minimum 6 hr discharge after anaphylaxis?
2 doses of IM adrenaline
Or previous biphasic reaction
Who has a minimum 12 hr discharge after anaphylaxis?
Severe reaction >2 IM adrenaline
Severe asthma
Possibility of on-going reaction
Presents late at night
Area where emergency access may be difficult
Observation for at least 2hrs following symptom resolution.
What concentration of adrenaline is used in anaphylaxis?
1 in 1000 IM
