4.9 Anaphylaxis

Question 1

What type of cell causes anaphylactic symptoms?

Answer 1

Mast cells

Question 2

What binds to mast cells?

Answer 2

IgE

Question 3

What are the main signalling molecules involved in anaphylaxis?

Answer 3

Histamines and leukotrienes

Question 4

What do histamines act on?

Answer 4

Blood vessels and smooth muscle

Question 5

What affect does histamine have in connective tissue?

Answer 5

Vasodilation with increased blood flow to surface and increased fluid movement out the blood stream (oedema)

Question 6

What affect does histamine have in mucosae?

Answer 6

Constriction of airways and contraction of smooth muscle in the intestine

Question 7

What causes mast cell degranulation?

Answer 7

IgE antibodies is already bound to Fc-epsilon-R1

Circulating antigen binds IgE, causing receptor crosslinking and degranulation

Question 8

How are IgE produced?

Answer 8

The CD4 T helper cells causes a class switch to IgE production

Question 9

What is an allergen?

Answer 9

An antigen which causes an allergic type IgE-mediated response

Question 10

What causes rashes and puffy skin seen in anaphylaxis?

Answer 10

Histamine causes vasodilation leading to red skin colour and oedema leading to raised appearance

Question 11

What is skin rash called?

Answer 11

Urticaria

Question 12

When can the localised skin reaction seen in allergy be useful?

Answer 12

In skin prick tests to see if allergens cause a wheal-and-flare reaction

Question 13

What is hay fever called?

Answer 13

Allergic rhinitis

Question 14

What causes Allergic Rhinitis?

Answer 14

Oedema in the epithelia lining the nose

Resulting in general irritation and mucus secretion

Question 15

What causes asthma?

Answer 15

When the allergen reaches the bronchioles of the lungs, resulting in contraction of smooth muscles which reduces the diameter of the airways

Leads to increased mucus production and difficulty breathing in and out

Question 16

What causes food allergies?

Answer 16

When an allergen is ingested, it acts on the mucosal mast cells in the intestinal tract, leading to vomiting and diarrhoea

If absorbed into blood stream, can cause rashes or itching

Question 17

What occurs in anaphylaxis which can be fatal and affect organ function?

Answer 17

A rapid decrease in blood pressure as the blood vessels dilate (shock)

Question 18

Why is adrenaline (epinephrine) given as an emergency treatment for anaphylaxis?

Answer 18

Adrenaline acts on alpha-adrenergic receptors to cause vasoconstriction and beta-adrenergic receptors for bronchodilation and redirects blood to organs to prevent shock

Question 19

After adrenaline, what medication is given following an anaphylactic shock?

Answer 19

Anti-histamines and anti-inflammatory corticosteroids like hydrocortisone

Question 20

If breathing problems persist after anaphylactic shock, what would be necessary?

Answer 20

Oxygen and bronchodilator given via inhaler (e.g. salbutamol)

Question 21

Why do patients feel faint follow an anaphylactic shock?

Answer 21

Due to the dramatic loss of blood pressure (hypotension)

Question 22

Why is blood pressure carefully measured after a shock?

Answer 22

Provides a reliable indication of recovery

Question 23

What is biphasic anaphylaxis?

Answer 23

When the symptoms return within hours of the initial reaction

Question 24

How long should patients with moderate respiratory/cardiovascular compromise should be observed before discharge?

Answer 24

8-10 hours