[PPT] - Emergency Medicine: Anaphylaxis Pathophysiology, differentials, PowerPoint Presentation

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Emergency Medicine: Anaphylaxis

Emergency series

Dr Shuaib Siddiqui, MB Bchir MRCP, FY3 Doctor

Content reviewed on the 14/05/2020.

Pathophysiology, differentials, investigations and management.

Cases Quiz

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History A 13-year-old boy attends the emergency department by ambulance, accompanied by his worried parents. His parents reveal he suddenly became wheezy whilst at a birthday party. He was unable to speak due to a swollen tongue. On examination, he is blue in the face with audible

stridor. There is an urticarial rash on his trunk

Observations HR 140, BP 88/45 mmHg, RR 28, SpO2 87%, Temp 37.2

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Case 1

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Question 1

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Question 2

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History A 13-year-old boy attends the emergency department by ambulance, accompanied by his worried parents. His parents reveal he suddenly became wheezy whilst at a birthday party. He was unable to speak due to a swollen tongue. On examination, he is blue in the face with audible

stridor. There is an urticarial rash on his trunk

Observations HR 140, BP 88/45 mmHg, RR 28, SpO2 87%, Temp 37.2

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Case 1

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Question 3

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Question 4

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Pathophysiology

Definition: rapid onset, life-threatening changes to airway, breathing and circulation due to a hypersensitivity reaction.

(1)

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Pathophysiology

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Pathophysiology

Degranulation

1. Life-threatening laryngeal

edema

3. Hypotension 2. Bronchospasm & increased mucous membrane secretion Stridor (+ respiratory distress) Wheeze (+ respiratory distress) Anaphylactic shock

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Pathophysiology

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Differential diagnoses

Allergic reaction Anaphylaxis

IgE mediated
Non IgE mediated

IgE mediated Requires sensitisation Requires sensitisation Systemically well ABC compromise Anaphylactoid Not antibody mediated Can occur on first exposure ABC compromise

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Question 5

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Pathophysiology

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Definition: rapid onset, life-threatening changes to airway, breathing and circulation due to a hypersensitivity reaction. Epidemiology

0.3% of people experience anaphylaxis in their lifetime (NICE)
Mortality < 1%

Risk factors

History of atopy: asthma, eczema, allergy
Food is a common allergen in children
Drugs are a common allergen in adults
Previous anaphylactic reaction
(Hygiene hypothesis)

Pathophysiology

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Pathophysiology

Clinical features

Symptoms Signs Exposure to allergen Hypotensive and tachycardic Angioedema:

Swelling of the face, tongue,

larynx, genitalia, hands and feet Tachypnoeic Pruritis and rash Stridor Dizziness Urticarial rash Syncope

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Pathophysiology

Clinical features

(2)

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Pathophysiology

Clinical features

(3)

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Question 6

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A-E assessment

Airways

Assess airway patency by asking patient to speak
Listen for evidence of obstruction e.g. stridor
Start with airway manoeuvres, such as a head tilt before airway adjuncts

(4) (5)

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A-E assessment

Breathing – Rule of 5 1. Observations:

2. Peripheral exam:
3. Central exam:
4. Urgent investigations:
5. Management:

Respiratory rate, oxygen saturations Peripheral cyanosis Tracheal deviation, percussion, auscultation ABG, CXR Oxygen therapy, nebulised therapy

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Circulation – Rule of 5 1. Observations:

2. Peripheral exam:
3. Central exam:
4. Urgent investigations:
5. Management:

Heart rate, blood pressure, fluid status CRT, pulse JVP, central CRT, auscultate ECG, cannula, bloods Fluids, vasopressors

A-E assessment

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Disability

1. GCS
2. Pupils
3. Glucose

Exposure

1. Top to toe examination of the patient

A-E assessment

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Question 7

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Question 8

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Adrenaline

Airway

Alpha agonist à vasoconstriction leads to reduction in laryngeal
edema

Breathing

Beta 2 agonist à bronchodilation

Circulation

Beta 1 agonist à increased cardiac contractility
Alpha agonist à vasoconstriction

Termination

Beta 2 agonist à inhibition of mast cells
Histamine antagonist

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Anaphylaxis protocol

Airways

The patient has stridor
Attempt airway manoeuvres
Give adrenaline

Breathing 1. Observations: RR 28, 87% O2

2. Peripheral exam: cyanosed
3. Central exam: cyanosed,

wheeze

4. Urgent investigations: CXR
5. Management: High flow
xygen

Dose: 0.5ml 1:1000 (0.5mg)

1:1000 = 1g in 1000mls = 1000mg in 1000mls = 1mg in

1ml

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Question 9

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Anaphylaxis protocol

Circulation 1. Observations: 88/45mmHg, HR140

2. Peripheral exam: weak pulse
3. Central exam: central CRT 4 seconds
4. Urgent investigations: cannula and

bloods

5. Management: IV access and bloods

Disability – patient may be unconscious Exposure – may find a rash

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Question 10

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Question 11

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Pathophysiology

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Primary investigations:

Mast cell tryptase

1) Immediately after treatment has commenced 2) 1-2 hours post-reaction 3) 24 hours post-reaction Outpatient investigations to consider:

Skin prick test
Skin patch test
Radioallergosorbent test (RAST)
Challenge test: contraindicated in anaphylaxis

Investigations

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Pathophysiology

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Skin prick test Skin patch test

Diluted food/pollen allergy is

placed on skin and pierced with needle

A wheal develops after 15 mins
Multiple allergens taped to the back
Assess for contact dermatitis after

48h

(6) (7)

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Question 12

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Pathophysiology

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Complications

Biphasic reaction:

Symptoms may return, usually within 6 hours of the initial episode,

without re-exposure to allergen Cardiorespiratory arrest:

Food: 30 mins
Insect sting: 15 mins
Medication: 5 mins

Recurrence:

A previous episode of anaphylaxis correlates with an increased risk of

a future anaphylactic reaction

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