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Signs and Symptoms
Airway: lip and tongue swelling/angioedema, hoarseness, stridor
Breathing: rapid breathing(tachypnoea), wheeze/ bronchospasm, fatigue, cyanosis, SpO2 < 92%, confusion due to hypoxia, cyanosis, respiratory arrest
Circulation: pale, clammy, hypotension, tachycardia, faintness, drowsy/coma, arrhythmia, myocardial ischemia, cardiac arrest, signs of shock
Skin: Urticaria and/or angioedema
There are a sensitization phase and an effector phase that give rise to the symptoms:
- Immune system encounters allergen and makes immunoglobulin E (IgE) against it
- No clinical features occur
- Allergen cross-links IgE on the surface of mast cells ( Type 1 hypersensitivity )
- Causes widespread degranulation and release of histamine which mediates inflammatory bronchospasm, vasodilatation, increased capillary permeability, and tissue edema
Common agents to cause anaphylaxis
- Medication: Antibiotics (Penicillin) , Aspirin, NSAIDs, Angiotensin Converting Enzyme Inhibitors, Anaesthetic agents, contrast media.
- Food Food, e.g. peanuts, egg and seafood.
- Insect stings
Mast cell tryptase: Take three samples taken- as soon as possible, after 1-2 hours (not later than 4 hours) and after 24 hours. Useful in making a retrospective diagnosis but the absence of rising does not exclude anaphylaxis
- C1 esterase inhibitor deficiency – autosomal dominant. Hereditary angio-oedema is not usually accompanied by urticaria and is treated with C1 esterase inhibitor/or fresh frozen plasma.
- Idiopathic (non-allergic) urticaria or angioedema
- Systemic mast cell disorders
- Septic shock presents with hypotension with a petechial/purpuric rash.
- Asthma can present with similar symptoms and signs to anaphylaxis, particularly in children.
|allergic Angioedema||Non-Allergic Angioedema||Anaphylaxis|
|Anatomically localised attack||Anatomically localised attack||Systemic symptoms|
|Urticaria||Gradual onset||Rapid onset and progression|
|Pruritis||No Pruritis||Respiratory failure (wheeze, fatigue, cyanosis, hypoxia, tachypnoea)|
|Normotension||Previous identical episodes||Cardiovascular Collapse (Diaphoretic, hypotensive, tachycardia, drowsiness)|
- Call for help, lie the patient flat and raise the patient’s legs
- Establish an airway if necessary and apply high flow oxygen
- Give IM Adrenaline- -Can be repeated after 5 min if no better
- In adults and children over 12 years, give 0.5ml(500 micrograms) of 1:1000 adrenaline
- In children aged 6-12 years, give 0.3ml (300 micrograms) of 1:1000 adrenaline intramuscularly.
- In children aged under 6 years, give 0.15ml (150 micrograms) of 1:1000 adrenaline intramuscularly.
- IV dose: Adults 50 micrograms; Children 1 microgram/kg (1:10,000 )(Risk of Cerebrovascular hemorrhage, Cardiac arrhythmias or infarction)
- Give only 50 % of the usual dose of adrenaline to patients taking tricyclic antidepressants, MAOIs, or B –blockers.
- Glucagon can be helpful in patients with anaphylaxis who are taking beta-blockers. 1–2mg IM/IV every 5min
- Give a crystalloid fluid bolus (A crystalloid may be safer than a colloid)
- Adults: 500-1000ml intravenously (4-8 L of crystalloid may be required peri-arrest)
- Children: 20ml/kg intravenously
Further management of anaphylaxis
- Observe for at least six hours
- Beware biphasic reactions
- Advise patient to return immediately if symptoms reoccur
- Admit under 16 years of age
- Provide three-day prescription of oral steroid and anti-histamine
- Consider an adrenaline auto-injecter (EpiPen)- 300mcg dose
- Referral to allergy specialist
What are relative contraindications while using adrenaline
Adrenaline may be administered in life-threatening anaphylactic reactions, even when the following relative contraindications are present:
- Coronary artery disease
- Uncontrolled hypertension
- Serious ventricular arrhythmias
- The second stage of labour
How does Adrenaline work?
- Adrenalines alpha-adrenoceptor actions reverse the peripheral vasodilatation and reduce oedema.
- It also has a beta-receptor action that causes airway dilation, increases the force of myocardial contraction and suppresses the histamine and leukotriene release