Anaphylaxis

Key points

Use ECAT protocols or Australasian Society of Clinical Immunology and Allergy (ASCIA) guidelines:

• Adult ECAT protocol: Anaphylaxis or allergic reactions
• Paediatric ECAT protocol: Anaphylaxis
• ASCIA guidelines: Acute management of anaphylaxis

Causes

Common triggers of anaphylaxis include:

• foods, e.g. nuts, milk, shellfish and eggs
• insect venom, e.g. wasp and bee sting
• medicines.

Assessment

History and examination

Obtain a patient history, noting:

• recent exposure to allergens
• known allergies, previous reactions and treatments
• history of anaphylaxis
• time of symptom onset.

Consider risk factors for fatal anaphylaxis (e.g. older age, cardiovascular and respiratory diseases) and cofactors that amplify reactions (e.g. exercise, acute infection).

Signs and symptoms of allergic reactions

Mild or moderate reactions

• Swelling of lips, face, eyes
• Hives or welts
• Tingling mouth
• Abdominal pain, vomiting (these are signs of anaphylaxis for insect allergy)

Anaphylaxis

Watch for any one of the following signs of anaphylaxis:

• Urticarial rash or erythema, flushing and/or angioedema
• Difficulty or noisy breathing
• Swelling of tongue
• Swelling and/or tightness in throat
• Difficulty talking and/or hoarse voice
• Wheeze or persistent cough
• Persistent dizziness or collapse
• Pale and floppy (young children)
• Vomiting and/or abdominal pain (for insect stings)

Management

Treatment

Treat patients with sudden breathing difficulty and a history of asthma and anaphylaxis as having anaphylaxis.

Monitor patients with allergy symptoms that do not meet anaphylaxis criteria to promptly recognize any progression to a severe allergic reaction.

Rule out differential diagnoses, such as acute asthma, syncope, panic attacks and septic shock.

Refer to ECAT protocols for anaphylaxis for adults and children. These protocols provide adrenaline dosing information.

Treatment priority

1. Remove allergen.  If still present.
2. Call for assistance. Follow local CERS pathway.
3. Lay patient flat. Do not allow them to stand or walk. If airway is compromised or breathing is difficult, allow patient to sit up. If vomiting, then place patient in left lateral position.
4. Give adrenaline IM into outer mid-thigh without delay. Can use autoinjector if available.
   In patients with known asthma and allergy to food, insects or medications, if there is sudden breathing difficulty (such as wheeze, persistent cough or hoarse voice):
   • Give IM adrenaline before asthma reliever, even if there are no skin symptoms.
   • Repeat every five minutes as needed.
   • If multiple doses are required or ongoing severe reaction, consider IV adrenaline infusion.
5. Supplemental oxygen.
6. Fluid resuscitation. IV fluid bolus of normal saline (20 mL/kg) and repeat as needed.

Persistent symptoms and overwhelming anaphylaxis

Persistent stridor – may respond to nebulised adrenaline (5mg in 5mL).

Persistent bronchospasm – may respond to bronchodilators and corticosteroids.

• If intubation is needed, continuous puffs of salbutamol into the circuit may help to relieve severe bronchospasm.
• corticosteroids, oral prednisolone 1mg/kg (max 50mg) or IV hydrocortisone 5mg/kg (max 200mg). These should not be used as first line.

Persistent hypotension – due to profound vasodilation or cardiac failure.

Cardiac arrest: overwhelming anaphylaxis – follow Australian and New Zealand Committee on Resuscitation Adult ALS algorithm or paediatric ALS algorithm

• Usually due to massive vasodilatation and fluid extravasation.
• IM adrenaline is unlikely to be absorbed due to poor peripheral circulation.
• IV adrenaline boluses and aggressive fluid resuscitation in addition to CPR.

Investigations

• Investigations are usually of little value in cases of mild or moderate anaphylaxis.
• Consider serial mast cell tryptase measurements during anaphylaxis to help identify the trigger when reviewed later.

Disposition

Patients who have responded to IM adrenaline should be observed for at least four hours after the last dose of adrenaline or overnight as appropriate.

Be aware that relapse, protracted and/or biphasic reactions may occur.

Patients will require overnight observation if they meet any of the following:

• Had a severe reaction (hypotension or hypoxia)
• Required repeated doses of adrenaline
• Have a history of severe asthma or protracted anaphylaxis
• Have other concomitant illnesses, such as asthma, chest infection or arrhythmia
• Live alone or are remote from medical care
• Have known systemic mastocytosis
• Presented for health care late in the evening
• Cannot easily replace their adrenaline injector on discharge and have no other adrenaline injector.

Discharge and follow up treatment

1. Discuss with patient and carer allergy avoidance.
2. Provide ASCIA action plans
3. Follow up with general practitioner and immunology allergy specialist review. All patients who present with anaphylaxis should be referred for specialist review.
4. Adrenaline autoinjector
   • If there is a risk of re-exposure (e.g. stings, foods, unknown allergen) then prescribe an adrenaline autoinjector prior to discharge or provide one from the hospital pharmacy. Teach patient how to use it.
   • Adrenaline auto-injectors (EpiPen) are expensive from the pharmacy without a pharmaceutical benefits scheme subsidy. Consider providing in the ED from hospital pharmacy prior to discharge.

Background

Anaphylaxis is characterised by a sudden onset (minutes to hours), however, the clinical presentation is variable. The diagnosis of anaphylaxis is based on clinical findings and takes the patient’s history and physical examination into consideration.

Adrenaline:

• narrows blood vessels preventing low blood pressure and shock
• opens airways, preventing and relieving airway swelling and wheeze
• reduces the release of allergy mediators, inhibiting the allergic response.

Despite this, studies show high rates of corticosteroid and antihistamine use for initial anaphylaxis treatment. This is concerning, as delaying adrenaline increases the risk of fatal anaphylaxis.

Resources

Clinical practice guidelines: Anaphylaxis
Paediatric Improvement Collaborative guideline covering assessment and management of anaphylaxis in children.
Source: Royal Children's Hospital Melbourne

Acute anaphylaxis clinical care standard
Recognise anaphylaxis and the provide appropriate treatment and follow-up care.
Source: Australian Commission on Safety and Quality in Health Care

Acute anaphylaxis clinical care standard implementation guide
Minimum requirements for local procedures on the management of acute anaphylaxis and the use of patient’s own adrenaline (epinephrine) autoinjectors.
Source: Clinical Excellence Commission