anaphylaxis Flashcards
What is anaphylaxis?
life-threatening medical emergency.
It is caused by a severe type 1 hypersensitivity reaction.
Immunoglobulin E (IgE) stimulates mast cells to rapidly release histamine and other pro-inflammatory chemicals. This is called mast cell degranulation.
Also leads to vasodilation = distributive shock
Capillary leaks = angio-oedema
This causes a rapid onset of symptoms, with airway, breathing and/or circulation compromise.
The key feature that differentiates anaphylaxis from a non-anaphylactic allergic reaction is compromise of the airway, breathing or circulation.
How does anaphylaxis present?
Patients present with a history of exposure to an allergen (although it can be idiopathic). There will be rapid onset of allergic symptoms:
Urticaria (skin rash)
Itching
Angio-oedema, with swelling around lips and eyes
Abdominal pain
- low BP & high HR w loss of consciousness sometimes
- cyanosis, stridor
Additional symptoms:
Shortness of breath
Wheeze (bronchospasm)
Swelling of the larynx, causing stridor
Tachycardia
Lightheadedness
Collapse
How is anaphylaxis managed?
Anaphylaxis requires immediate medical attention and management. It should be managed by an experienced paediatrician. Call for help early. Refer to the resuscitation guidelines for full management guidelines.
Initial assessment of acutely unwell child is with an ABCDE approach, assessing and treating:
A - Airway: Secure the airway ; intubate if needed
B - Breathing: Provide oxygen if required. Salbutamol can help with wheezing.
C - Circulation: Provide an IV bolus of fluids
D - Disability: Lie the patient flat to improve cerebral perfusion
E - Exposure: Look for flushing, urticaria and angio-oedema
Once a diagnosis of anaphylaxis is established, there are three medications given to treat the reaction:
Intramuscular adrenalin, repeated after 5 minutes if required
Antihistamines, such as oral chlorphenamine or cetirizine
Steroids, usually intravenous hydrocortisone
Resolution of anaphylaxis
Observe 6-12 hours
On discharge:
- warn about biphasic reaction
- avoid any triggers
- 2 pre-loaded 300 microgram adrenaline autoinjectors as interim until clinic
Causes of anaphylaxis?
- food ; peanuts, eggs, fish
- drugs ; penicillin, NSAIDs, opioids
- bee/wasp stings
- latex
What is done after anaphylaxis event?
All children should have a period of assessment and observation after an anaphylactic reaction, as biphasic reactions can occur, meaning they can have a second anaphylactic reaction after successful treatment of the first. Children should be admitted to the paediatric unit for observation.
Anaphylaxis can be confirmed by measuring the serum mast cell tryptase within 6 hours of the event. Tryptase is released during mast cell degranulation and stays in the blood for 6 hours before gradually disappearing.
Education and follow-up of the family and child is essential. They need to be educated about allergy, how to avoid allergens and how to spot the signs of anaphylaxis. Parents should be trained in basic life support. Specialist referral should be made in all children with anaphylaxis for diagnosis, education, follow up and training in how to use an adrenalin auto-injector.
Remember to measure mast cell tryptase within 6 hours of an anaphylactic reaction
Adrenalin Auto-injector
Epipen, Jext and Emerade are trade names for adrenalin auto-injector devices.
They are given to all children and adolescents with anaphylactic reactions. They may also be considered in children with generalised allergic reactions (without anaphylaxis) with certain risk factors:
Asthma requiring inhaled steroids
Poor access to medical treatment (e.g. rural locations)
Adolescents, who are at higher risk
Nut or insect sting allergies are higher risk
Significant co-morbidities, such as cardiovascular disease
