See also:

Emergency drug and fluid calculator 
Resuscitation 
Asthma 
Urticaria

Key Points

1. Definition: Anaphylaxis is a multi-system allergic reaction characterised by:
   • Any acute onset illness with typical skin features (urticarial rash or erythema/flushing, and/or angioedema), PLUS
   • Involvement of respiratory and/or cardiovascular symptoms and/or persistent severe gastrointestinal symptoms
   • OR Any acute onset of hypotension or bronchospasm or upper airway obstruction where anaphylaxis is considered possible, even if typical skin features are not present.
2. Do not allow children with anaphylaxis to stand or walk.
3. Treatment of anaphylaxis is intra-muscular adrenaline 10 micrograms/kg or 0.01ml/kg of 1:1000 (maximum 0.5ml), into lateral thigh which should be repeated after 5 minutes if the child is not improving.
4. Recognise and address, if possible, risk factors for fatal anaphylaxis, including
• Adolescence
• Nut and shellfish allergy
• Poorly controlled asthma
• Delays to administration of adrenaline or emergency services

Background

Most reactions occur within 30 minutes of exposure to a trigger but can occur up to 4 hours.

• Foods - Peanut, tree nuts, cow milk, eggs, soy, shellfish, fish, wheat
• Bites/stings - Bee, wasp, jack jumper ants
• Medications-  Beta-lactams
• Other - exercise, idiopathic

Assessment

Identify risk factors for fatal anaphylaxis

• Poorly controlled asthma (see Asthma)
• Allergy to nuts, shellfish, drugs and insect stings
• Adolescence
• Delay to administration of adrenaline or emergency response services
• Pre-existing cardiac and respiratory conditions

Anaphylaxis is a clinical diagnosis. A detailed history, particularly of pre-hospital events, is vital to identifying anaphylaxis and its associated trigger, as often some symptoms are transient and resolve prior to arrival in the acute care setting.

Respiratory/chest features (most common in children)

• Persistent cough
• Wheeze
• Tongue swelling
• Stridor 
• Hoarse voice or change in character of the cry
• Subjective feeling of swelling or tightness/tingling in the throat
• Dysphagia

Cardiovascular features

• Pale and floppy (infant)
• Palpitations
• Tachycardia
• Bradycardia
• Hypotension
• Collapse with or without unconsciousness
• Cardiac arrest

Neurological features

• Headache (usually throbbing)
• Dizziness
• Altered consciousness/confusion

Gastrointestinal features

• Nausea
• Vomiting
• Diarrhoea
• Abdominal/pelvic pain

Dermatological features

• Urticarial rash
• Erythema/flushing
• Angioedema

Management

• Remove allergen (if still present)
• Posture: Do not allow the child to stand or walk. Fatality can occur within seconds if the child stands or sits suddenly. Treat the child in the supine position, or the left lateral position for a vomiting child (or sitting upright if breathing is difficult, but monitor for hypotension).
• Intramuscular adrenaline 10 micrograms/kg or 0.01 ml/kg of 1:1000 (maximum 0.5 ml), into lateral thigh which should be repeated after 5 minutes if the child is not improving.
• Do not use SC adrenaline, as absorption is less reliable than the IM route.
• Do not use IV bolus adrenaline unless cardiac arrest is imminent. 
• Use an adrenaline autoinjector if unable to calculate exact dose or to avoid delay, including in children <1 year old.

The following doses of adrenaline may be used if the weight is unknown:

• If the child is not improving after repeated doses of IM adrenaline (>2 doses), consult local senior staff (e.g. ICU/anaesthetics, discuss with PIPER) and consider adrenaline infusion (0.05-5 mcg/kg/min).
• While establishing IV access, continue giving IM adrenaline every 5 minutes.

Peripheral IV Adrenaline Infusion:

This should only be run for a maximum of 1-2 hours (to avoid fluid overload), and in consultation with PIPER/specialist PICU input:

• Mix 1 mL of 1:1000 adrenaline in 1000 mL of normal saline
• Start infusion at 5 mL/kg/hr (~0.1 microgram/kg/minute)
• Titrate dose according to response
• Monitor continuously
• If possible, insert a second IV for fluid boluses, if needed. 

• If hypotensive, resuscitate with fluid; repeated boluses of 20 ml/kg of 0.9% saline may be required for shock.
• Nebulised adrenaline is not recommended as first-line therapy, but may be a useful adjunct to IM adrenaline if upper airway obstruction or bronchospasm is present (commonly used in children).
• If airway oedema is not responding to parenteral and nebulised adrenaline, early intubation is indicated.

Investigations

Anaphylaxis is a clinical diagnosis. A serum tryptase has no role in acute management of anaphylaxis. It should only be ordered after consultation with a paediatric allergy specialist in special circumstances.

Treatment

Other treatments to consider

• Nebulised or MDI salbutamol is recommended if the child has respiratory distress with wheezing and consider other anti-asthma medications (see asthma).
• Antihistamines may be given for symptomatic relief of pruritus. Second generation antihistamines are preferred (avoid promethazine as it can cause hypotension).
• Corticosteroids, antihistamines and leukotriene antagonists have no proven immediate benefit on life threatening anaphylaxis.

Observation and Admission

All children with anaphylaxis should be observed for at least 4 hours in a supervised setting with facilities to manage deterioration.

Admission for a minimum 12 hour period of observation is recommended if:

• Further treatment is required within 4 hours of last adrenaline administration (biphasic reaction)
• Previous history of biphasic reaction
• Poorly controlled asthma
• The child lives in an isolated location with delay to emergency services 

The acute care setting should provide resources, education and follow up options to the family including:

• Update the medical record highlighting suspected allergen to avoid
• Anaphylaxis action plans (in red, not black and white)
• 2 EpiPen/EpiPen Jnr® and training in correct use with an Epipen trainer. Current dose recommendations are:  
• <20 kg = EpiPen Jnr® (150 µg)
• > 20 kg = EpiPen® (300 µg).
  EpiPen®/EpiPen Jnr® are available on PBS for all children with a history of acute anaphylaxis.   See Guidelines for the prescription of an EpiPen for more information.
  Epipen requires authority prescription or can be purchased without a prescription at full cost.   See PBS authority indications.
• Consider provision of a  Medicalert bracelet .
• Print parent information sheets from ASCIA
• All children with anaphylaxis should be referred to a paediatric allergy specialist. Review is ideal as soon as possible after the episode (Victorian paediatric specialists)
• Ensure that asthma control is addressed including diagnosis, action plan, and preventers, as asthma is an independent risk factor for fatal anaphylaxis (see asthma). 

Consider consultation with local paediatric team when:

• Children at high risk of fatal anaphylaxis. 

Consider transfer when:

• Inadequate adrenaline response
• Multiple doses of adrenaline
• Adrenaline infusion
• Immediate life-threatening situations
• A child requiring care beyond the comfort level of the hospital
  

For emergency advice and paediatric or neonatal ICU transfers, call the Paediatric Infant Perinatal Emergency Retrieval (PIPER) Service: 1300 137 650.

Consider discharge when:

• See observation and admission

Parent information sheet

• Allergic and anaphylactic reactions (including autoinjectors)
  
• Allergyfacts.org.au
• www.allergy.org.au

Last revised August 2017