Anaphylaxis and allergy Flashcards Preview

Pediatrics > Anaphylaxis and allergy > Flashcards

Flashcards in Anaphylaxis and allergy Deck (31):
1

Definition

Acute, severe, life threatening allergic reaction in pre-sensitised individual leading to a systemic response caused by inflammatory mediator response by mast cells/basophils At least 2 organ systems involved->skin, upper/lower respiratory tract, CV, neurological, GI systemcs

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Most frequent causative agents

Medicines Food ++ peanut tree nuts, cow milk, eggs, soy, shell fish, wheat Immunotherapy Insect stings Exercise, idiopathic, latex, tranfusion

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When similar symptoms are due to non-immunological mechanisms

Anaphylactoid

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Lifetime prevalence

0.5-2%

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Respiratory responses

smooth muscle spasm in the respiratory and gastrointestinal (GI) tracts, vasodilation, increased vascular permeability, and stimulation of sensory nerve endings. Increased mucous secretion and increased bronchial smooth muscle tone, as well as airway edema

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Cardiovascular response

-ve vascular tone +permeability

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Pathogenesis

Allergen exposure->IgE produced= sensitisation->subsequent exposure->degranulation of mast cells releasing: Histamine, prostaglandin D2, leukotrienes, platelet-activating factor, tryptase, nitric oxide, and eosinophil and neutrophil chemotactic factors vascular permeability, vasodilation, and myocardial dysfunction hypotension and cardiovascular collapse, as up to 50% of intravascular volume can shift to the extravascular compartment in minutes. Altered smooth muscle tone results in bronchospasm and asthma in the respiratory tract, and may also lead to uterine cramps. Activation of the autonomic nervous system causes tachycardia, anxiety, and mucus hypersecretion. Increased platelet aggregation and subsequent recruitment of more immune cells complete the picture of the systemic inflammatory response.

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Classification of immediate-type, life-threatening allergic/pseudoallergic

1. IgE antibody mediated w/ systemic 2. IgE with local, life threatening laryngeal edema 3. Immunological, not IgE->anaphylotoxins C3a, C5a, MAB against lymphocytes 4. Munchausenas- real or factitious 5. Anaphylactoid: clinically indistinguishable from anaphylaxis, IgE not seen->radiocontrast, NSAID 6. Idiopathic

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Features of idiopathic anaphylaxis

cause cannot be identified generalised frequent: >6 episodes per year, or ≥2 episodes within a 2-month period generalised infrequent: less often than generalised frequent angio-oedema (potentially life-threatening) frequent: >6 episodes per year or ≥2 episodes within a 2-month period angio-oedema (potentially life-threatening) infrequent: less often than angio-oedema frequent.

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High risk

History of anaphylaxis Multiple allergies Poorly controlled asthma Pre-existing lung disease

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Respiratory features

Respiratory/chest features (Most common in children) Tongue swelling Stridor Hoarse voice or change in character of the cry Subjective feeling of swelling or tightness/tingling in the throat Persistent cough Wheeze Dysphagia

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Gastrointestinal features

NVD Pain

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Mucocutaneous features

Generalised pruritus Urticaria/ intense erythema Conjunctival erythema and tearing Flushing Angioedema Neurological features Headache (usually throbbing) Dizziness Confusion Collapse with or without unconsciousness

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Investigations

Anaphylaxis is a clinical diagnosis

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Management

1. ABCD call for help 2. Posture: treat the patient in supine position, or left lateral position for vomiting patient (or sitting at 45 degrees if breathing is difficult Legs should be elevated in the setting of hypotension. Do not stand. 3. Intra-muscular adrenaline 0.01ml/kg of 1/1000 (maximum 0.5ml), into lateral thigh which should be repeated after 5 minutes if patient not improving. 4. High flow Oxygen Do not use subcutaneous adrenaline, as absorption is less reliable than the intramuscular route. Do not use IV bolus adrenaline unless cardiac arrest is imminent. 5. An adrenaline infusion (0.05 - 1mcg/kg/min) if repeated doses of IM adrenaline are required. 6. Resuscitate boluses 20 ml/kg of 0.9% saline may be required for shock. 7. Nebulised adrenaline is not recommended as first-line therapy, but may be a useful adjunct to IM adrenaline if upper airway obstruction is present. 8. If airway oedema is not responding to parenteral and nebulised adrenaline, early intubation is indicated. 9. Corticosteroids, antihistamines and antileukotrienes have no proven immediate benefit on life threatening anaphylaxis. They may improve mild cutaneous symptoms. Other therapies to consider 10. Nebulised salbutamol is recommended if the patient has respiratory distress with wheezing or consider other anti asthma medications. 11. Antihistamines may be given for symptomatic relief of pruritus. Second generation antihistamines are preferred (promethazine can cause hypotension). 12. Corticosteroids may be considered at the discretion of the treating physician, especially for bronchospasm, although the limited evidence available does not support their use.

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Managment when partial obstruction

High flow oxygen 1:1000 Adrenaline 0.01ml/kg IM, repeat every 5 minutes if necessary Nebulised adrenaline 1:1000 5ml, repeat as required Notify ICU/anaesthetics if not improving Consider corticosteroids

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Management when complete obstruction

Bag-mask ventilation with high flow O2 Intubation or laryngeal mask or surgical airway Adrenaline IM (IV if respiratory or cardiac arrest)

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Management when wheeze

High flow oxygen 1:1000 Adrenaline 0.01ml/kg IM Nebulised salbutamol as needed Consider corticosteroids Manage as for severe/critical asthma if not improving

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Management when apnoeic

Bag-mask 1/1000 Adrenalin 0.01ml/kg IM

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Management when no pulse

Resuscitation

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Management when in shock

High flow oxygen Keep patient supine, or at 45° if breathing difficulty 1:1000 Adrenaline 0.01ml/kg IM Repeat adrenaline every 5 minutes as necessary 0.9% Saline 20ml/kg IV boluses as necessary Consider adrenaline infusion

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How long should children be observed for following anaphylaxis

At least four hours

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When to consider admission

any of the following circumstances apply: Greater than one dose of adrenaline (including nebulised adrenaline) required. A fluid bolus required. Inadequate response to treatment. The child lives a long distance from medical services.

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D/C plans when considered high risk of recurrent anaphylaxis

Anaphylaxis action plans Epipen + have been trained Need authority prescription Medicalert bracelet ?Referral to pediatric allergy specialist

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Dosing of epipen

20 kg = EpiPen® (300 µg).

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When to transfer to tertiary

Inadequate adrenalin Multiple adrenalin Adrenlin infusion Immediate life threatening situation Child requiring care above that which can be managed at that hospital

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Action plan for anaphylaxis with epipen

Recognise mild/moderate:

-swollen lips, face, eyes

-hives, welts

-tingling mouth

-abdominal pain, vomiting

Plan: 

-stay with person, call for help

-locate autoinjector

-phone emergency contact

Watch for:

-difficulty breathing, swollen tongue, swelling/tight chest, hoarse voice, wheeze, cough, dizzy, collapse, pale/floppy child

ACTION

1. lay person flat

2. Give epipen

3. Phone ambulance

4. Phone emergency

5. Further adrenalin may be given if no response after 5 minutes

CPR at any time they are non responsive

 

 

 

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Action plan for allergic reaction

Action plan

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If not sure whether anaphylaxis or asthma, plan

Give adrenalin first, then inhaler

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Giving epipen

Fist around epipen

Pull off safety blue release

Place orange end against outer mid thigh

Push down hard until click, hold in place for 10 seconds

Remove epipen and massage site for 10 seconds

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