Anaphylaxis

https://www.allergy.org.au/hp/papers/acute-management-of-anaphylaxis-guidelines

1. Definition and Clinical Diagnostic Criteria for Anaphylaxis

• ASCIA Definition: Anaphylaxis is defined as:
  • Any acute onset illness with skin features (urticarial rash, erythema/flushing, and/or angioedema), plus respiratory and/or cardiovascular involvement, or severe GI symptoms.
  • Acute onset of hypotension, bronchospasm, or upper airway obstruction, even without typical skin features.
• World Allergy Organization Criteria:
  • Criteria 1: Acute onset (minutes to hours) involving skin/mucosal tissue and at least one of:
    • Respiratory compromise (e.g., dyspnea, bronchospasm, hypoxemia).
    • Reduced BP/end-organ dysfunction (e.g., hypotonia, syncope).
    • Severe GI symptoms (e.g., severe abdominal pain, repetitive vomiting).
  • Criteria 2: Acute onset of hypotension, bronchospasm, or laryngeal involvement after allergen exposure, even if skin symptoms are absent.

Anaphylaxis is highly likely when any 1 of the following 3 criteria are fulfilled:

(1) Acute onset of an illness (minutes to several hours) with involvement of the skin, mucosal tissue, or both – Localised to area of contact (eg perioral) or widespread generalized hives – pruritus or flushing – Angioedema/swollen lips-tongue-uvula AND at least 1 of the following: (i) Respiratory compromise –  difficulty breathing, persistent coughing, tightness in throat. chest tightness, difficulty swallowing Dyspnea, stridor, hypoxemia , wheeze-bronchospasm, Hoarse voice (ii) Reduced BP or associated symptoms of end-organ dysfunction – hypotonia [collapse], syncope, incontinence

(2) Two or more of the following that occur rapidly after exposure to a likely allergen for that patient (minutes to several hours): (i) Involvement of the skin-mucosal tissue- Localised to area of contact (eg perioral) or widespread generalized hives, pruritus or flushing, Angioedema/swollen lips-tongue-uvula (ii) Respiratory compromise- Dyspnea , wheeze-bronchospasm, stridor, reduced PEF, hypoxemia (iii) Reduced BP or associated symptoms – hypotonia [collapse], syncope, incontinence (iv) persistent gastrointestinal symptoms – crampy abdominal pain, vomiting

(3) Reduced BP after exposure to known allergen for that patient (minutes to several hours): Infants and children: – low systolic BP (age specific) or  – greater than 30% decrease in systolic BP Adults: – systolic BP of less than 90 mm Hg or  – greater than 30% decrease from that person’s baseline

2. Signs and Symptoms of Allergic Reactions

• Mild to Moderate Reactions:
  • Swelling of lips, face, eyes.
  • Hives or welts.
  • Tingling mouth.
  • Abdominal pain, vomiting (especially after insect stings or drug injection).
• Anaphylaxis:
  • Difficult or noisy breathing.
  • Swelling of tongue.
  • Throat swelling/tightness.
  • Hoarse voice, difficulty talking.
  • Wheeze or sudden persistent cough.
  • Persistent dizziness, collapse.
  • Pale, floppy (in young children).
  • Abdominal pain, vomiting (after insect stings or drug injection).

3. Immediate Actions for Anaphylaxis

ALWAYS give adrenaline FIRST, then asthma reliever if someone with known asthma and allergy to food, insects or medication has SUDDEN BREATHING DIFFICULTY (including wheeze, persistent cough or hoarse voice) even if there are no skin symptoms.

• Remove Allergen: Remove the allergen if still present; stay with the patient and call for help.
• Patient Positioning:
  • Lay the patient flat; do not allow standing or walking.
  • If unconscious or pregnant, place in the left-side recovery position.
  • If breathing is difficult, allow sitting with legs outstretched.
  • Hold young children flat, not upright.
• Administer Adrenaline IM (1st Line Treatment):
  • Use adrenaline autoinjector if available, otherwise, adrenaline ampoule and syringe.
  • Dose: 0.01 mg/kg (up to 0.5 mg per dose) IM in outer mid-thigh.
• Additional Support:
  • Give oxygen if available.
  • Phone ambulance (000 in AU or 111 in NZ) for transport if not in a hospital.
  • Further adrenaline doses if no improvement after 5 minutes.
  • Begin CPR if unresponsive and not breathing.
  • Always give adrenaline first, then asthma reliever if needed.
  • If accidental adrenaline injection occurs, contact poison information.

4. Anaphylaxis Triggers and Reaction Times

• Common Triggers: Foods, insect stings, and medications.
• Less Common Triggers: Latex, tick bites, exercise (with or without food), cold, radiocontrast agents, immunisation.
• Timing:
  • Food Allergy: Typically within 1-2 hours; reactions to mammalian meat and food-dependent exercise anaphylaxis may be delayed.
  • Stings/Injected Drugs: Usually within 5-30 minutes but can be delayed.

5. Adrenaline Administration and Dosages

• IM Adrenaline (1:1,000) is the first-line treatment.
• Dosage by weight (outer mid-thigh):
  • <7.5 kg: 0.1 mL.
  • 7.5-20 kg: 150 microgram device (0.15 mL).
  • 20-50 kg: 300 microgram device (0.3 mL).
  • 50 kg or >12 years: 0.5 mL.
• Repeat every 5 minutes if necessary; consider adrenaline infusion in severe cases.
• Do not use adrenaline 1:10,000 for IM doses.

Adrenaline (epinephrine) dose chart
Age (years)	Weight (kg)	Volume (mL) of adrenaline 1:1,000 ampoules*	Adrenaline injector devices                (for use instead of ampoules)
~<1	<7.5	0.1 mL	Not available
~1-2	10	0.1 mL	7.5-20 kg (~<5yrs)150 microgram device**
~2-3	15	0.15 mL
~4-6	20	0.2 mL
~7-10	30	0.3 mL	>20 kg (~>5yrs)300 microgram device***
~10-12	40	0.4 mL
~>12 and adults	>50	0.5 mL	>50 kg (~12 years)500 microgram**** or 300 microgram devices

6. Management of Anaphylaxis in Pregnancy and Infants

• Pregnancy: Adrenaline is the first line, with the patient positioned in left lateral.
• Infants:
  • A 150 microgram device is recommended for infants 7.5 kg or more.
  • Limit to 2-3 doses to avoid hypertension and tachycardia.

7. Positioning of Patients with Anaphylaxis

• Do Not Stand or Walk: Maintain the patient in a lying position.
• For patients with respiratory symptoms, sitting with legs outstretched may improve breathing.
• Left Lateral Position: Recommended for unconscious or pregnant patients.
• Infants: Hold flat, not upright

8. Equipment for Acute Management of Anaphylaxis

• Emergency trolley items:
  • Adrenaline 1:1,000 ampoules.
  • Syringes (1mL) and needles (22-25 G, 25 mm).
  • Oxygen, airway equipment, masks, suction.
  • Defibrillator and blood pressure cuff.
  • IV access equipment (large bore cannulae).
  • Normal saline (at least 3 liters).
  • Hands-free phone for remote communication.

9. Supportive Management and Additional Measures

• Monitoring: Pulse, BP, ECG, pulse oximetry, consciousness.
• Oxygen: High-flow oxygen for respiratory distress.
• IV Access in hypotensive adults and children.
• Fluid Resuscitation: IV normal saline 20mL/kg for hypotension.
• Advanced Measures:
  • IV adrenaline infusion if no response after 2-3 doses or patient deteriorates.
  • Avoid IV adrenaline bolus due to arrhythmia risk unless in cardiac arrest.
• Additional Treatment for:
  • Upper airway obstruction: Nebulised adrenaline (5 mL of 1:1,000).
  • Persistent wheeze: Salbutamol and corticosteroids (not first line for anaphylaxis).
• AVOID:
  • Antihistamines have no role in treating or preventing respiratory or cardiovascular symptoms of anaphylaxis. 
  • Do not use oral sedating antihistamines as side effects (drowsiness or lethargy) may mimic some signs of anaphylaxis. 
  • Injectable promethazine should not be used in anaphylaxis as it can worsen hypotension and cause muscle necrosis.

10. Actions After Adrenaline Administration

Observation: Minimum 4 hours post-last adrenaline dose.

Extended Monitoring:

• Overnight observation if:
  • Severe or prolonged anaphylaxis.
  • History of severe reactions.
  • Concurrent illness (e.g., asthma, arrhythmia).
  • Living alone or far from medical care.
  • Late evening presentation.
• Biphasic Reactions: Occur in 3-20% of cases; overnight monitoring is advised.

Adrenaline Injector Prescription & Training:

• Prescribe an adrenaline injector if re-exposure to allergens (e.g., stings, foods) is likely, or if idiopathic anaphylaxis occurred.
• Provide hands-on injector training with a trainer device.
• Complete an ASCIA Action Plan for Anaphylaxis from ASCIA.

Referral to Clinical Immunology/Allergy Specialist:

• Referral is essential for all anaphylaxis patients to:
  • Confirm allergen(s).
  • Educate on avoidance, management, and comorbidities.
  • Provide ASCIA Action Plan for future episodes.
  • Initiate allergen immunotherapy if available.
  • Refer to additional professionals (e.g., dietitian) as needed.

ASCIA Anaphylaxis Resources: Resources for community anaphylaxis management and e-training are accessible at ASCIA.

Documentation of Episodes: Patients should document each anaphylactic episode using the ASCIA allergic reactions event record to track avoidable causes.

Patient and Carer Support: Referral to support organizations for information and guidance:

• Allergy & Anaphylaxis Australia
• Allergy New Zealand

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Advanced Acute Management of Anaphylaxis

Supportive Management (When Skills and Equipment Are Available)

• Vital Signs Monitoring:
  • Continuous assessment of pulse, blood pressure, respiratory rate, pulse oximetry, and level of consciousness.
• Oxygen Administration:
  • Indications: All patients with respiratory distress, reduced consciousness, or those requiring repeated doses of adrenaline.
  • Dosage: High-flow oxygen (6-8 L/min) should be administered via a non-rebreather mask.
  • Consideration: Supplemental oxygen is recommended for patients with chronic respiratory disease (e.g., asthma) or cardiovascular conditions.
• IV Access:
  • Establish intravenous (IV) access in adults and children with hypotension.
  • Fluid Resuscitation for Hypotension:
    • Administer IV normal saline at 20 mL/kg rapidly, repeat as necessary if hypotension persists.
    • Consider additional wide bore IV access (14 or 16 gauge for adults) due to risk of significant fluid extravasation into tissues.

Monitoring for Overtreatment Risks

• Signs of Overtreatment:
  • Be alert for pulmonary edema, hypertension, especially in patients who initially did not present with hypotension or respiratory distress.
• Measurement of Systolic Blood Pressure (SBP):
  • Palpable SBP: Attach a manual BP cuff, locate the brachial or radial pulse, and measure the pressure at which the pulse disappears and reappears, indicating the “palpable” SBP.
  • Children: This method may be more challenging in younger patients.
• Adrenaline Toxicity vs. Worsening Anaphylaxis:
  • If the patient is experiencing nausea, tremors, vomiting, or tachycardia with a normal or elevated SBP, consider adrenaline toxicity rather than a worsening anaphylactic response.

Additional Measures – IV Adrenaline Infusion

• Indications: For severe cases unresponsive to intramuscular (IM) adrenaline or cases of clinical deterioration.
• Administration Protocols:
  • Pre-Hospital Settings:
    • Mix 1 mL of 1:1,000 adrenaline in 1,000 mL of normal saline.
    • Initial rate: ~5 mL/kg/hour (~0.1 microgram/kg/min).
    • If an infusion pump is unavailable, use a standard giving set (~20 drops per mL), starting at ~2 drops per second for an adult.
  • Emergency Departments/Tertiary Hospital Settings:
    • Mix 1 mL of 1:1,000 adrenaline in 100 mL of normal saline.
    • Initial rate: ~0.5 mL/kg/hour (~0.1 microgram/kg/min).
    • Should be administered only with an infusion pump.
• Monitoring:
  • Continuous ECG and pulse oximetry.
  • Frequent non-invasive blood pressure checks to adjust dosage as needed and prevent overtreatment and adrenaline toxicity.
• Important Considerations:
  • Dedicated line with an infusion pump and anti-reflux valves is advised.
  • Avoid indefinite continuation of low-concentration infusions to minimize fluid overload.
• Caution: IV bolus doses of adrenaline are generally NOT recommended outside of cardiac arrest due to the risk of cardiac ischemia and arrhythmia.

Additional Interventions for Ineffective IV Adrenaline Infusion

• Persistent Hypotension or Shock:
  • Administer normal saline up to 50 mL/kg within the first 30 minutes.
• Glucagon for Cardiogenic Shock:
  • Indicated especially for patients on beta-blockers.
  • Dosage:
    • Adults: 1-2 mg IV bolus.
    • Children: 20-30 micrograms/kg (up to 1 mg) IV bolus.
  • May be repeated or followed by a continuous infusion of 1 mg/hour in adults if necessary.
• Selective Vasoconstrictors:
  • Adults: Consider metaraminol (2-10 mg) or vasopressin (10-40 units) only with specialist guidance due to risks of arrhythmias, severe hypotension, and pulmonary edema.
  • Children: Metaraminol at 10 micrograms/kg/dose may be used with caution.
  • Noradrenaline Infusion: Recommended only in critical care with invasive blood pressure monitoring.

Advanced Airway Management

• Priority on Oxygenation:
  • Oxygenation is prioritized over intubation.
• Preferred Methods:
  • Utilize the basic airway support methods most familiar to the provider (e.g., jaw thrust, Guedel or nasopharyngeal airway, bag-valve-mask with high-flow oxygen).
  • Avoid prolonged intubation attempts, as these can delay oxygen delivery.
• Cricothyrotomy:
  • Consider as a last-resort measure for maintaining an airway when standard measures fail, especially if oxygen saturation is falling.
  • Specialized Training Requirement: Providers must be trained in advanced airway procedures to perform cricothyrotomy effectively.

Special Situation: Overwhelming Anaphylaxis Leading to Cardiac Arrest

• Unique Pathophysiology:
  • Characterized by massive vasodilation and extensive fluid leakage into tissues.
  • IM adrenaline absorption is likely impaired due to poor peripheral circulation in this setting.
• Intervention Protocol:
  • IV Adrenaline Bolus:
    • Administer 1 mg every 2-3 minutes per cardiac arrest protocol.
  • Aggressive Fluid Resuscitation:
    • IV normal saline at 20 mL/kg via large bore IV access under pressure, repeat if there is no response.
  • CPR Duration:
    • Prolonged CPR may be beneficial due to the potentially reversible nature of anaphylaxis-related cardiac arrest and pre-arrest oxygenation levels.

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Assessment

• History
  • Timing of reaction in relation to food ingestion
  • Duration of symptoms
  • Exact foods eaten, how much and in what form (eg raw, cooked)
  • Other foods ingested at the time
  • Age when symptoms first occurred and frequency of occurrence
  • Reproducibility on repeat exposures
  • Details of previous treatment (eg antihistamines) and response
• Risk factors for development of IgE-mediated food allergy
  • Personal history of atopy (asthma, eczema or allergic rhinitis)
  • History of atopy or food allergy in parents or siblings
  • Known other IgE-mediated food allergies

Examination

• Acute presentation
  • Airway – hoarseness, stridor, tongue swelling, laryngeal oedema
  • Breathing – tachypnoea, cough, wheeze
  • Circulation – tachycardia, hypotension
  • Skin – rashes, urticaria and angioedema

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Differential diagnosis of conditions that mimic anaphylaxis

• Tissue swelling
  • Idiopathic urticaria
  • Isolated angioedema
    • Idiopathic
    • Angiotensin-converting enzyme inhibitor-induced
    • Acquired or hereditary C1 esterase inhibitor deficiency
• Conditions mimicking upper airway oedema
  • Dystonic reactions mimicking symptoms of a swollen tongue
  • Acute oesophageal reflux (sudden onset of painful throat “swelling”)
• Flushing syndromes
  • Peptide-secreting tumours (eg, carcinoid syndrome, VIPomas)
  • Alcohol-related
  • Medullary carcinoma of thyroid
  • Red man syndrome (associated with vancomycin infusion)
• Neurological syndromes
  • Epileptic seizure
  • Stroke
• Other causes of collapse
  • Vasovagal episodes
  • Systemic inflammatory response syndrome
  • Shock due to other causes
• Acute respiratory distress
  • Asthma
  • Panic disorders
  • Globus hystericus
  • Laryngospasm
  • Vocal cord dysfunction
• Food Protein Induced Enterocolitis Syndrome (FPIES)
  • profuse vomiting +/- diarrhoea occurring two to four hours after ingestion of a recently-introduced food. 
  • Sometimes associated with pallor, poor tone, a drop in body temperature and low blood pressure. 
  • FPIES is non-IgE mediated
• Miscellaneous
  • Scombroid fish poisoning
  • Serum sickness
  • Phaeochromocytoma
  • Systemic mastocytosis

Education

• On strict avoidance of suspected food allergen
• education on reading ingredient labels ( ASCIA Dietary avoidance handouts)
• specific advice for suspected tree-nut allergies:
  • if reacted to walnuts, avoid pecans and vice-versa
  • if reacted to cashews, avoid pistachios and vice-versa
• If there is uncertainty an oral food challenge may be considered. 
• Where multiple foods are to be avoided, dietician referral is recommended
• teach use of adrenaline auto-injector
• optimal control of asthma  – the vast majority of fatalities from food anaphylaxis (75–98%)
  occur in asthmatics, which suggests that optimal asthma control is another important management aim.
• Survival tips for people with food allergy
  • Know your allergy triggers
  • Be educated in careful dietary avoidance
  • Have excellent asthma control
  • Carry injectable adrenaline at all times and be confident in its use
  • Get a ‘buddy’: make sure a friend or relative knows what to do in the event of a reaction
  • When eating out, telephone ahead to notify friends or restaurants of your allergy
  • When eating ‘allergen free’ food you haven’t prepared yourself: ‘touch test’ on the lip before eating

• Consultation with local paediatric/allergy team when
  • To all patients with life threatening allergic features attributed to food exposure
  • Child with suspected allergy and unstable asthma
  • Unclear food trigger or equivocal investigations
  • Multiple food allergies
• Suspected tolerance to food on follow-up and which may require an Oral Food Challenge
• ASCIA Travel Plan Anaphylaxis
• ASCIA PC Checklist Anaphylaxis Travel

Desensitisation therapy/ Allergen immunotherapy 

• Evidence that food allergy can be controlled in this way is very limited, although research is ongoing.
• Most food allergy immunotherapy methods are not currently approved for routine treatment of food allergy globally.
• Current only recommendations are for
  • for the treatment of potentially life threatening allergic reactions to stinging insects.
    • bee
    • wasp
    • Jack Jumper Ant
  • for treatment of allergic rhinitis (hay fever) due to
    • pollen
    • dust mite
      • when:
        • Symptoms are severe.
        • The cause is difficult to avoid, such as grass pollen.
        • Medications don’t help or cause adverse side effects.
        • People prefer to avoid medications