What is anaphylaxis?
A life-threatening systemic hypersensitivity reaction that causes vasodilation, bronchoconstriction and angioedema as a result of sudden and excessive release of the chemical mediators such as histamine.
What does the systemic hypersensitivity reaction cause?
Vasodilation, bronchoconstriction and angioedema
What causes the vasodilation, bronchoconstriction and angioedema?
Sudden and excessive release of histamine
What phases occur during anaphylaxis?
Sensitisation phase and secondary response phase
Explain the sensitisation phase:
- Antigen (allergen) invade the body via injection, inhalation, ingestion or absorption.
- Common allergens include food, insect bites/stings and medications
- Plasma cells synthesize and release large amounts of immunoglobin E (IgE) antibodies
- IgE antibodies attach to MAST cells and circulating Basophils
Explain the secondary response phase:
- On re-exposure, antigen combine with IgE on MAST cells and basophils, triggering a release of histamine, prostaglandin and leukotrienes.
- These mediators rapidly induce bronchoconstriction, hyper secretion of mucus and vasodilation causing oedema.
AIRWAY signs and symptoms of anaphylaxis
- Throat/tongue swelling
- Difficulty breathing and swallowing
- Hoarse voice
- Stridor
BREATHING signs and symptoms of anaphylaxis
- Bronchospasm
- Tachypnoea/dyspnoea
- Wheeze
- Fatigue
- Confusion due to hypoxia
- Cyanosis
- Sats <92%
- Respiratory arrest (last sign)
CIRCULATION signs and symptoms of anaphylaxis
- Hypotension
- Tachycardia
- Pale and clammy skin
- Dizziness
- Decreased conscious level
- Myocardial infarction
- Bradycardia (late sign)
- Cardiac arrest (late sign)
OTHER signs and symptoms of anaphylaxis
- Skin/mucosal changes (Urticaria/flushing)
- Diarrhoea and/or vomiting
- Abdominal pain
- Anxiety
Anaphylaxis risk factors
- Family history
- Previous anaphylaxis
- Asthma
Differential diagnosis to consider for anaphylaxis?
- Asthma
- Anxiety attack
- MI
ASSESSMENT - Anaphylaxis
DRA(c)BCDE
Danger? Mechanism of Injury? Catastrophic Bleeding?
- Assess for any potential dangers
- Remove any potential triggers
- Manage any bleeds
Response
AVPU - assess
Airway
- Clear?
- Any swelling?
- Correct if compromised
C-Spine
Is this a concern based on MOI?
Breathing
- Rate and depth of respiration?
- Wheeze?
- Stridor?
- Assist with ventilation if required
Circulation
- Heart rate?
- Palpable radial pulse?
- Oxygen Saturations?
- Blood pressure - Hypotension?
- Capillary refill?
- Skin colour - flushed?
- Corrected if necessary
Disability
- Temperature
- Blood glucose?
- PEARL
- Equal and bilateral air entry
- 12 lead ECG
- Alerted GCS
Examine
- Oedema?
- Signs of trigger?
- Flushed skin?
- Hives
Past Medical History
- Has this happened before?
- Are they allergic to anything?
- Have they taken an EpiPen?
Treatment:
Treat as per JRCALC
- Correct any ABC problems immediately
Severe Anaphylaxis Treatment
- Administer oxygen if saturations are below 94%
- Administer adrenaline IM (1:1000- 500 mcg – no max)
- Consider fluids if patient is hypotensive (systolic below 90)
- Consider chlorphenamine (antihistamine) (4mg in 1 tablet- max 4mg)
- Consider administering hydrocortisone (suppresses inflammation) (200mg injected over 2 mins – max 200mg)
- Consider nebulised salbutamol for bronchospasm (5mg – 6/8 litres per minute – no max)
Pre-alert and convey to A&E with continuous monitoring, treatment and reassessment.
