2.19 Anaphylaxis

Question 1

What type of hypersensitivity reaction is anaphylaxis?

Answer 1

Type I hypersensitivity.

Question 2

How severe is anaphylaxis compared to other hypersensitivity reactions?

Answer 2

It is the most severe form — a life-threatening systemic allergic reaction.

Question 3

What causes anaphylaxis?

Answer 3

A massive, systemic release of histamine and other mediators from mast cells in response to an allergen.

Question 4

Which immune cells primarily release histamine during anaphylaxis?

Answer 4

Mast cells.

Question 5

What happens when histamine is released systemically instead of locally?

Answer 5

It causes widespread vascular and respiratory effects that can be fatal if untreated.

Question 6

How does histamine affect blood vessels during anaphylaxis?

Answer 6

It increases vascular permeability and causes vasodilation.

Question 7

What happens when capillary endothelial cells open up due to histamine?

Answer 7

Fluid leaks out of the blood vessels into tissues, leading to edema and loss of blood volume.

Question 8

How does loss of intravascular fluid during anaphylaxis affect blood pressure?

Answer 8

It decreases blood pressure and reduces perfusion to organs and the brain.

Question 9

What happens to the airways during anaphylaxis?

Answer 9

Bronchoconstriction — the bronchioles tighten, narrowing the airways.

Question 10

What symptom is typically heard during anaphylaxis due to airway constriction?

Answer 10

Expiratory wheezing caused by narrowed bronchioles.

Question 11

Why might someone’s tongue or lips swell during anaphylaxis?

Answer 11

Because of widespread vascular permeability and systemic edema.

Question 12

What type of shock can result from severe anaphylaxis?

Answer 12

Anaphylactic shock — a combination of vasodilation, fluid loss, and airway obstruction.

Question 13

What medication is used as the first-line treatment for anaphylaxis?

Answer 13

Epinephrine (adrenaline).

Question 14

How is epinephrine typically administered during anaphylaxis?

Answer 14

Injected intramuscularly, or in severe cases, directly into the heart.

Question 15

What is the primary goal of epinephrine treatment in anaphylaxis?

Answer 15

To reverse bronchoconstriction and reduce vascular permeability.

Question 16

How does epinephrine affect the bronchioles?

Answer 16

It relaxes bronchial smooth muscle, opening the airways for easier breathing.

Question 17

How does epinephrine affect the cardiovascular system?

Answer 17

It increases heart rate and stroke volume, helping circulate remaining blood effectively.

Question 18

How does epinephrine counteract histamine’s effects on blood vessels?

Answer 18

It decreases vasodilation and vascular permeability, stabilizing blood pressure.

Question 19

What physiological change does epinephrine cause to support circulation?

Answer 19

It increases cardiac output by making the heart pump faster and harder.

Question 20

Why is epinephrine life-saving during anaphylaxis?

Answer 20

It reverses airway constriction, restores blood pressure, and supports perfusion to vital organs.