Anaphylaxis Flashcards
What is anaphylaxis?
Anaphylaxis is an acute allergic reaction from IgE cross linking triggering mast cell degranulation.
Briefly describe the pathophysiology of anaphylaxis
It is caused by a severe type 1 hypersensitivity reaction. Immunoglobulin E (IgE) stimulates mast cells to rapidly release histamineand other pro-inflammatory chemicals. This is called mast cell degranulation. This causes a rapid onset of symptoms, with airway, breathing and/or circulation compromise.
What allergens can cause anaphylaxis?
Causes of anaphylaxis include:
- Insect stings
- Nuts
- Other food (shellfish, fish)
- Antibiotics
- IV contrast
- Other medications
What features differentiate between anaphylaxis and a non-anaphylactic allergic reaction?
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
- Itching
- Angio-oedema, with swelling around lips and eyes
- Abdominal pain
Additional symptoms that indicate anaphylaxis are:
- Shortness of breath
- Wheeze
- Swelling of the larynx, causing stridor
- Tachycardia
- Lightheadedness
- Collapse
Briefly describe the assessment of anaphylaxis
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
- 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 anaphylaxis is confirmed. What 3 medications can be given to treat anaphylaxis?
Intramuscular adrenalin, repeated after 5 minutes if required.
Antihistamines, such as oral chlorphenamine or cetirizine.
Steroids, usually intravenous hydrocortisone.
What is the dose of adrenaline needed for anaphylaxis?
The dose of adrenaline varies according to age:
- 150 micrograms of 1:1000 is for children under 6
- 300 micrograms is for children 6-12
- 500 micrograms is for children over 12 and adults
Why do children need to be monitored after an anaphylactic reaction?
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.
What investgiation can be done after an anaphylactic reaction to confirm this?
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.
Why is education and follow up important after an anaphylactic reaction?
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.
What are the indications for an 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
Briefly describe how to use an adrenalin auto-injector
The first step is to confirm the diagnosis of anaphylaxis.
Prepare the device by removing the safety cap on the non-needle end. There is a blue cap on EpiPen and a yellow cap on Jext.
Grip the device in a fist with the needle end pointing downwards. The needle end is orange on EpiPen and black on Jext. Do not put your thumb over the end, because if the device is upside down you will inject your thumb with adrenalin and could risk losing it.
Administer the injection by firmly jabbing the device into the outer portion of the mid thigh until the device clicks. This can be done through clothing. EpiPen advise holding it in place for 3 seconds and Jext advise 10 seconds before removing the device.
Remove the device and gently massage the area for 10 seconds.
Phone an emergency ambulance. A second dose may be given (with a new pen) after 5 minutes if required.
