Anaphylaxis and allergy

Question 1

Definition

Answer 1

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

Question 2

Most frequent causative agents

Answer 2

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

Question 3

When similar symptoms are due to non-immunological mechanisms

Answer 3

Anaphylactoid

Question 4

Lifetime prevalence

Answer 4

0.5-2%

Question 5

Respiratory responses

Answer 5

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

Question 6

Cardiovascular response

Answer 6

-ve vascular tone +permeability

Question 7

Pathogenesis

Answer 7

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.

Question 8

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

Answer 8

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

Question 9

Features of idiopathic anaphylaxis

Answer 9

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.

Question 10

High risk

Answer 10

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

Question 11

Respiratory features

Answer 11

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

Question 12

Gastrointestinal features

Answer 12

NVD Pain

Question 13

Mucocutaneous features

Answer 13

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

Question 14

Investigations

Answer 14

Anaphylaxis is a clinical diagnosis

Question 15

Management

Answer 15

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.

Question 16

Managment when partial obstruction

Answer 16

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

Question 17

Management when complete obstruction

Answer 17

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

Question 18

Management when wheeze

Answer 18

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

Question 19

Management when apnoeic

Answer 19

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

Question 20

Management when no pulse

Answer 20

Resuscitation

Question 21

Management when in shock

Answer 21

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

Question 22

How long should children be observed for following anaphylaxis

Answer 22

At least four hours

Question 23

When to consider admission

Answer 23

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.

Question 24

D/C plans when considered high risk of recurrent anaphylaxis

Answer 24

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

Question 25

Dosing of epipen

Answer 25

20 kg = EpiPen® (300 µg).

Question 26

When to transfer to tertiary

Answer 26

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

Question 27

Action plan for anaphylaxis with epipen

Answer 27

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

Question 28

Action plan for allergic reaction

Answer 28

Action plan

Question 29

If not sure whether anaphylaxis or asthma, plan

Answer 29

Give adrenalin first, then inhaler

Question 30

Giving epipen

Answer 30

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