Anaphylaxis

Question 1

Define anaphylaxis

Answer 1

A rapidly developing life-threatening airway and/or breathing and/or circulatory problems usually associated with skin and mucosal changes

Question 2

What are the risk factors for anaphylaxis?

Answer 2

<30 years old for food associated and exercise-induced anaphylaxis
History of atopy or asthma
History of anaphylaxis
Exposure to a common sensitiser e.g. healthcare workers being exposed to latex

Question 3

Explain the pathophysiology of sensitisation to an allergen

Answer 3

On first exposure to an allergen, the allergen will be picked up by a dendritic cell and presented to a T cell which then stimulates a B cell to produce IgE antibodies against the allergen. These antibodies are released into the bloodstream and bind to. the surface of mast cells and basophils

Question 4

Describe the pathophysiology of anaphylaxis post-sensitisation

Answer 4

In a sensitised individual, subsequent exposure to an allergen causes allergen binding to IgE antibodies causing degranulation of mast cells and basophils. Histamine from these cells causes blood vessel dilation, increased permeability and smooth muscle contraction. Tryptase acts to break down proteins causing tissue injury. Cytokines attract additional immune cells

Question 5

Describe the pathophysiology on non-IgE mediated anaphylaxis

Answer 5

Mast cell and basophil degranulation is stimulated directly without the involvement of IgE
This could be immune mediated e.g. some blood products can bind to circulating antigens to form immune complexes which activate complement proteins which triggers mast cell degranulation
Contrast medium and opioids can cause direct non-immune mediated degranulation

Question 6

How does anaphylaxis cause shock?

Answer 6

Immune mediators depress myocardial function directly, cause vasodilation and cause leakage of fluid from capillary blood vessels into the extra-vascular compartment

Question 7

How does anaphylaxis cause airway obstruction?

Answer 7

Fluid leaks from the capillary blood vessels and causes tissue swelling
Altered smooth muscle tone results in bronchospasm and asthma

Question 8

Food allergens are some of the most common causes of anaphylaxis. Which foods are common allergens?

Answer 8

Egg
Milk
Peanuts
Nuts
Fish and Shellfish

Question 9

Anaphylaxis caused by food allergens is most common in what age group?

Answer 9

Children

Question 10

Drug-induced anaphylaxis is most common in what age group?

Answer 10

Adults

Question 11

What is meant by food-associated exercise-induced anaphylaxis?

Answer 11

Anaphylaxis occurs when a patient exercises within 2-4 hours of ingestion of a specific food

Question 12

Which drugs most commonly cause anaphylaxis?

Answer 12

Penicillins
NSAIDs
Contrast Media
Opiates

Question 13

List common triggers of anaphylaxis?

Answer 13

Food - eggs, milk, peanuts, nuts, fish and shellfish
Latex
Drugs - NSAIDs, penicillins, radio-contrast media, opiates
Bites and stings - spider, wasps, ant, bees
Exercise
Idiopathic
Seminal fluid

Question 14

What are the 3 criteria for the diagnosis of anaphylaxis?

Answer 14

Sudden onset and rapid progression of symptoms usually developing over minutes
Life threatening airway, breathing or circulation problems
Usually also skin / mucosal changes present

Question 15

What findings of anaphylaxis may be found on assessment of a patient’s airway?

Answer 15

Throat and tongue swelling with difficulty breathing and swallowing
Hoarse voice
Stridor

Question 16

What findings of anaphylaxis may be found on assessment of a patient’s breathing?

Answer 16

Increased respiratory rate
Wheeze
Confusion caused by hypoxia
Patient feels tired
Cyanosis 
Respiratory arrest

Question 17

What findings of anaphylaxis may be found on assessment of a patient’s circulation?

Answer 17

Signs of shock - blue cold peripheries, CRT >3. secs, veins undefiled or collapsed due to hypovolaemia, tachycardia, blood pressure normal or low, reduced level of consciousness
Low blood pressure with feeling of fairness / dizziness or collapse
Chest pain with ECG changes
Bradycardia and cardiac arrest

Question 18

What findings of anaphylaxis may be found on assessment of disability in a patient?

Answer 18

Airway, breathing and circulatory problems can affect neurological status leading to confusion, agitation and loss of consciousness
GI symptoms - abdominal pain, nausea, vomiting and incontinence

Question 19

What findings of anaphylaxis may be found on assessment of exposure in a patient?

Answer 19

Skin / mucosal changes are often the first presenting feature
Erythema and urticaria
Angio-oedema, swelling of the deeper tissues including eyelids, lips, mouth and throat

Question 20

In which patients with anaphylaxis should a mast cell tryptase test be used?

Answer 20

Patients aged 16+

Patients aged <16 if trigger is not food-related

Question 21

Ideally 3 mast cell tryptase measurements should be taken for patients in anaphylaxis. When should each of these measurements be taken?

Answer 21

One as soon as possible after resuscitation
One 1-2 hours after the start of symptoms
24 later to act as a baseline

Question 22

What investigations should be used for patients with anaphylaxis?

Answer 22

Mast cell tryptase
12-lead ECG
U&Es
ABGs
CXR

Question 23

What is the immediate management of anaphylaxis?

Answer 23

IM adrenaline and removal of the trigger

Supportive management with 15L oxygen on. trauma mask, IV fluid challenge

Question 24

How. should the patient be positioned in anaphylaxis?

Answer 24

Lie down, legs up

Question 25

How much fluid should be given to a patient in anaphylaxis?

Answer 25

500-1000ml crystalloid fluid in adults

20ml/kg crystalloid fluid in children

Question 26

If after two doses of IM adrenaline, IV or nebuliser adrenaline can be given in anaphylaxis. T/F?

Answer 26

True - but this should only be done by a senior doctor

Question 27

Besides adrenaline and fluid, what other drugs can be given in anaphylaxis?

Answer 27

Antihistamine e.g. chlorphenamine

Corticosteroids e.g. hydrocortisone

Question 28

Anaphylaxis may cause a biphasic reaction. T/F?

Answer 28

True