Anaphylaxis Flashcards
What type of reaction is anaphylaxis caused by?
A severe type 1 hypersensitivity reaction.
What happens in a type 1 hypersensitivity reaction?
Immunoglobulin E (IgE) stimulates mast cells to rapidly release histamine and other pro-inflammatory chemicals (mast cell degranulation).
This causes a rapid onset of symptoms, with airway, breathing and/or circulation compromise.
What is the key feature that differentiates anaphylaxis from a non-anaphylactic allergic reaction?
The compromise of the airway, breathing or circulation.
Presentation of anaphylaxis?
Patients present with a history of exposure to an allergen (although it can be idiopathic).
Symptoms:
- Urticaria
- Itching
- Angio-oedema, with swelling around lips and eyes
- Abdominal pain
Additional symptoms:
- Shortness of breath
- Wheeze
- Swelling of the larynx, causing stridor
- Tachycardia
- Lightheadedness
- Collapse
Management of anaphylaxis?
ABCDDE approach.
Once a diagnosis of anaphylaxis is established, there are three medications given to treat the reaction:
1) IM adrenaline
2) Antihistamines e.g. oral chlorphenamine or cetirizine
3) Steroids: usually IV hydrocortisone
What 3 medications are indicated in anaphylaxis?
1) IM adrenaline
2) Antihistamines, such as oral chlorphenamine or cetirizine
3) Steroids
What steroid is typically given in anaphylaxis?
IV hydrocortisone
What dose adrenaline is given in anaphylaxis?
IM adrenaline (1:1000) 0.50ml
When can administration of adrenaline be repeated in anaphylaxis?
Repeat administration every 5 minutes if the patient remains haemodynamically unstable (max 5mL).
Recommended site for adrenaline injection in anaphylaxis?
he anterolateral aspect of the middle third of the thigh.T
If the patient remains haemodynamically unstable after 2 doses of adrenaline, what is then indicated?
Then an adrenaline infusion may be required (this will be a consultant/critical care led decision).
Overview of management of anaphylaxis
A - Secure airway
B - Can give nebulised bronchodilators if there is suspicion of bronchospasm (e.g. wheezing on auscultation)
C - IM adrenaline, IV fluids
D
E - antihistamines, allergen removal
What fluids are indicated in anaphylaxis?
Patients with anaphylaxis require urgent fluid resuscitation:
1) Administer an initial bolus of 500-1000ml Hartmann’s solution or 0.9% sodium chloride over less than 15 mins.
2) Re-assess the patient after each fluid bolus and administer further boluses as required (large volumes of fluid may be required in the context of anaphylaxis).2
What is refractory anaphylaxis?
Defined as respiratory and/or cardiovascular problems persist despite 2 doses of IM adrenaline.
Management of refractory anaphylaxis?
1) IV fluids should be given for shock
2) Expert help should be sought for consideration of an IV adrenaline infusion
Which antihistamines are indicated in anaphylaxis?
Non-sedating oral antihistamines (e.g. cetirizine) can be used to treat skin symptoms once the patient has been stabilised.
What can be given in anaphylaxis following initial stabilisation especially in patients with persisting skin symptoms (urticaria and/or angioedema)?
Non-sedating antihistamines e.g. cetirizine (i.e. NOT chlorphenamine)
What blood test can be done in anaphylaxis?
Serum tryptase
Purpose of serum tryptase test in anaphylaxis?
Can help establish severity of anaphylaxis.
All children should have a period of assessment and observation after an anaphylactic reaction, as biphasic reactions can occur.
What are biphasic reactions?
They can have a second anaphylactic reaction after successful treatment of the first.
How can anaphylaxis be confirmed?
Anaphylaxis can be confirmed by measuring the serum mast cell tryptase within 6 hours of the event.
What is tryptase?
Tryptase is released during mast cell degranulation and stays in the blood for 6 hours before gradually disappearing.
How long after an anaphylactic reaction must tryptase be measured?
Within 6 hours
What are all children and adolescents with anaphylactic reactions given?
Adrenalin auto-injector devices e.g. Epipen, Jext and Emerade
