Hypersensitivity

Question 1

What are mediators of allergic reactions (Type I IgE-mediated) and what do they do?

Answer 1

• -histamine
• -complement: more inflammatory cells and cytokines
• -acetylcholine: bronchiole smooth muscle contraction
• -leukotrienes: delayed and more prolonged, similar to histamine
• -prostaglandins
• -kinins: vasodilate, smooth muscle contraction
• -eosinophils: show up in allergic rxn, attract more leukocytes and eosinophils

Question 2

What is atopy and what can cause it?

Answer 2

local rxn
genetic predisposition to the development of immediate, type I IgE mediated hypersensitivity reactions upon exposures to common environmental antigen such as pollens, food, or animal dander

Question 3

How to atopic reactions typically manifest?

Answer 3

urticarial (hives)
allergic rhinitis
atopic dermatitis
bronchial asthma

Question 4

What are the two defined phases of type I hypersensitivity reactions? What occurs in each phase and when does each occur?

Answer 4

1. primary/initial: vasodilation, vascular leakage, smooth muscle contraction
   occurs 5-30 min after exposure, subsides w/in 60 min
2. secondary/late-phase: more intense infiltration of tissues with eosinophils and other acute and chronic inflammatory cells as well as tissue destruction in the form of epithelial cell damage
   occurs: 2-8 hours after initial phase, can last several days

Question 5

What does histamine do in the type I hypersensitivity inflammatory response? Is it released in the primary or secondary phase?

Answer 5

-potent vasoactive amine
-increases nitric oxide production
-relaxes vascular smooth muscle
-increases permeability of capillaries and venules
-causes smooth muscle contraction
-bronchiole constriction
Release: primary

Question 6

What does acetylcholine do in type I IgE inflammatory response? Is it released in the primary or secondary phase?

Answer 6

-bronchial smooth muscle contraction
-dilation of small blood vessels via parasympathetic nervous system
-mimics many actions of histamine
Released: primary

Question 7

What do kinins do in type I IgE inflammatory response? Is it released in the primary or secondary phase?

Answer 7

-potent inflammatory peptides
-produce vasodilation
-smooth muscle contraction
Released: primary

Question 8

What chemicals are released in the second, or late phase of a type I hypersensitivity reaction?

Answer 8

leukotrienes and prostaglandins

provide similar effects as histamine, but longer lasting and delayed

Question 9

What do you consider investigating if a pt presents with chronic urticaria? (if patients h and p suggests associated disease)

Answer 9

thyroid

h. pylori

Question 10

Anaphylaxis could include local responses and?

Answer 10

• life threatening reaction from release of histamine into systemic circulation that produces massive vasodilation, hypertension, arterial hypoxia, and airway edema
• hives
• angioedema

Question 11

When does the late-stage response from anaphylaxis occur?

Answer 11

sometimes occurs and onset is several hours after exposure

Question 12

What meds do the late-stage anaphylactic response best respond to?

Answer 12

steroids, but also give H1 and H2 inhibitors

Question 13

Anaphylaxis: What are the sx a pt will present with?

Answer 13

• -generalized pruiritis, flushing and sense of impending doom
• -urticaria and angioedema
• resp tract involvement (wheezing, SOB, laryngeal edema) 50% result in resp failure
• anaphylactic shock occurs in 30% of cases

Question 14

Anaphylactic shock occurs in 30% of cases. What happens in this stage?

Answer 14

• -cardiovascular collapse from hypovolemia
• -alterations in peripheral vascular resistance
• -myocardial depression

Question 15

How does cardiovascular collapse result from hypovolemia?

Answer 15

–due to increased vascular permeability and loss of up to 50% of blood volume

Question 16

What is management of anaphylaxis?

Answer 16

• -Depends on severity–
• stabilization (may include: intubation, IV’s w/fluid)
• oxygen
• **epinephrine (drug of choice b/c reverse hypotension and bronchospasm)
• antihistamines H1 and H2
• bronchodilators
• corticosteroids (helps w/ late phase rxn)

Question 17

Why do you give steroids to anaphylaxis patients?
Why do you give Benadryl?
Will volume hurt the patient?

Answer 17

Steroids = delayed rxn
Benadryl = histamine blocker
volume will not hurt pt b/c pt is not a heart failure pt

Question 18

What are the common drug allergies?

Answer 18

Beta-lactam abx (penicillins, cephalosporins)

• sulfonamides (trimethoprim/sulfamethoxazole [bactrim/septra])
• phenytoin
• carbamazepine (Tegretol)
• allopurinol
• NSAIDs (Ibuprofen, Aleve)

Question 19

What is drug is most commonly known for causing stevens-johnsons syndrome?

Answer 19

sulfonamides (trimethoprim/sulfamethoxazole [bactrim/septra])

Question 20

What are the classic drug reaction patterns?

Answer 20

More mild:
-urticaria
-angioedema
More serious manifestations:
-anaphylaxis
-drug-induced exanthems (rash)
--hypersensitivity vasculitis
-Stevens-Johnson syndrome
-erythema multiforme
-photosensitivity

Question 21

How long will it take to manifest sx in a patient that takes a drug they are allergic to?

Answer 21

• -Depends on whether they have been previously sensitized–
• -previously sensitized = rapid development sx
• -no previously sensitized =may takes days to develop or may not appear until next exposure

Question 22

What is the fundamental question to ask anytime someone presents with an allergic reaction?

Answer 22

Are there systemic symptoms, especially shortness of breath? (losing air? swelling in face?)

Question 23

What should anaphylactic patients always have?

Answer 23

Epi-pens

Question 24

What is the treatment of choice in Type I hypersensitivity reactions–allergic rhinitis? (not including significant breathing problems)

Answer 24

antihistamines

Question 25

What are the two most important mediators to think about when it comes to mediator specific medications with type 1 hypersensitivity?

Answer 25

histamines and leukotrienes

Question 26

What works well for allergic rhinitis? When should the pt start taking it?

Answer 26

• nasal steroids (REMEMBER THESE DONT BLOCK HISTAMINE, but work well to decrease inflammation)
• need to take before allergies start

Question 27

What are symptoms of allergic rhinitis?

Answer 27

• rhinorrhea (runny nose)
• nasal obstruction
• sneezing
• nasal itching
• watery eyes (conjunctivitis)

Question 28

People with allergic rhinitis frequently present with other forms of atopy including?

Answer 28

allergic asthma

urticaria

Question 29

Severe AR attacks may be accompanied by systemic:

Answer 29

malaise, fatigue, headache, and muscle soreness from sneezing

Question 30

Do people with allergic rhinitis present with fevers?

Answer 30

No

Question 31

What are the typical allergens that cause allergic rhinitis?

Answer 31

pollens from rage, grasses, trees, and weeds
fungal sporse
house dust mite
animal dander
feathers

Question 32

What are the most common foods that produce hypersensitivities?

Answer 32

peanuts, tree nuts, selfish, milks