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Multisystem > Allergy and Anaphylaxis > Flashcards

Allergy and Anaphylaxis Flashcards

1
Q

What is anaphylaxis?

A

An exaggerated immune mediated hypersensitivity reaction that leads to systemic histamine release, increased vascular permeability and vasodilation.

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2
Q

How does anaphylaxis present?

A
  1. Rapid onset and progression of Sx
  2. Life threatening compromise of:
    - Airway (breathing / swallowing / stridor)
    - Breathing (SOB, hypoxemia, resp arrest)
    - Circulation (tachycardia, hTN, decreased urine output)
  3. Involvement of skin (erythema, urticaria) / mucosa (angiooedema, obstruction, GIT Sx)
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3
Q

What are the most common allergens precipitating anaphylaxis?

A
  • Food (nuts, seafood)
  • Stings
  • Drugs (penicillin, NSAIDs, ACEi, anaesthetics)
  • Contrast media
  • blood products
  • latex
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4
Q

DDx anaphylaxis?

A
  • Asthma

- Septic shock

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5
Q

Immediate Mx anaphylaxis?

A

IMMEDIATE

  • Airway control + O2
  • 0.5mL Adrenaline 1:1000
  • Remove agent
  • IV Fluids: bolus 1000mL crystalloid
  • Monitoring
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6
Q

Secondary treatment anaphylaxis?

A
  • Diphenhydramine (Benadryl) 50mgIM or IV q4-6h
  • Methylprednisolone 50-100mg IV
  • Salbutamol if bronchospasm
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7
Q

When and why is it important to monitor patient after resolution of anaphylaxis?

A

Monitor for 4-6h ED; then r/v LMO 24-48h

Can have biphasic rxn up to 48h later.

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8
Q

Medications post anaphylaxis?

A

3 day course:

i) H1 antagonist (cetirizine or benadryl)
ii) H2 antagonist (ranitidine)
iii) corticosteroids (prednisone 50mg for 5/7)

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9
Q

What is an allergy?

A

Innappropriate/harmful mine response to foreign substances that are otherwise not harmful, mediated mostly by IgE.

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10
Q

What are allergens?

A

Generally proteins that elicit an IgE response in allergic individuals.

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11
Q

What is a clinical allergy?

A

Clinical allergy = symptoms + demonstration of specific IgE (skin test or RAST)

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12
Q

What are the diagnostic allergy tests?

A
  • Skin prick tests
  • Serologic assays (e.g. RAST)
  • Challenge testing
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13
Q

What are the advantages of SPT?

A
  • Highly sensitive
  • in vivo allergen exposure
  • Convenient; results in
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14
Q

Disadvantages of SPT?

A
  • Potential for anaphylaxis
  • May lack specificity (sensitised by asymptomatic individuals; irritant false positive rxns)
  • Specialist clinic required
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15
Q

How do serologic assays work?

A

Measure allergen specific IgE.

Allergen

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16
Q

What are the advantages of in vitro assays?

A

E.g. IgE serum - RAST etc.

  • Availability (GPs can do)
  • Safety
  • Specific at high level
  • Standardised
17
Q

Disadvantages of in vitro assays?

A
  • Interpretation depends on pre test probability (FP 5-10%)
  • Elevated total IgE (e.g. eczema) may give false postives
  • medicare only subsidised 4 tests at one time
18
Q

When are challenge tests used?

A

When RAST and SPT negative/discordant and good clinical story.

19
Q

How are allergies treated?

A 
Allergen SPECIFIC:
-allergen avoidance
-allergen specific immunotherapy
NON SPECIFIC
-antihistamines/ steroids
-adrenaline
-leukotriene antagonists
-anti IgE Abx (omalizumab)
20
Q

What is allergen immunotherapy?

A

S/C allergen injections. Only current allergy therapy to provide improvement / cure.
Efficacy limited by side effects.

21
Q

Main indication for SC injection immunotherapy?

A
  • Venom allergy (bee, wasp)
  • Allergic rhinitis
  • Mild, well controlled allergic asthma
22
Q

What are the RFx for fatal food related anaphylaxis?

A
  • Associated asthma
  • Lack of epipen
  • young adults
  • EtOH
  • Extreme sensitivity
23
Q

Describe the mechanism of bee sting?

A
  • Sting via barbed modified ovipositor which is left in the skin
  • Only sting once
  • Each sting deposits 35-200mcg venom
24
Q

Describe wasp sting.

A
  • Nests in concealed locations
  • Most aggressive toward end of summer
  • Can sting multiple times
  • 10-20mcg venom per sting
25
Q

Treatment of insect sting allergy.

A

Immunotherapy (95% efficacy with vespid, 80% bee venom).

  • 5y therapy duration
  • Epipen carried until -ve sting rxn
26
Q

In whom is latex allergy most common?

A

Health care workers, spina bifida patients.

27
Q

Symptoms of latex allergy?

A
  • Urticaria
  • Rhinits
  • Asthma
  • Anaphylaxis
  • Contact dermatitis
28
Q

Which foods are latex allergens cross reactive with?

A
  • Banana
  • Avo
  • Kiwi
29
Q

Main drugs causing allergy/anaphylaxis?

A
  • ABx: penicillins, cephalosporins
  • Contrast agents: (anaphylactoid = non-IgE mediated)
  • Anaesthetic agents: esp msucle relaxants
  • NSAIDs
  • CAMs e.g. echinacea
30
Q

What is urticaria?

A

Circumscribed, slightly elevated intensely pruritic skin lesions.
Initially erythematous but can develop central pallor as oedema develops in dermis.

31
Q

What is angiooedema?

A
  • Non-pruritic, less erythematous (Cf urticaria)
  • Clearly defined swelling occurring in deep dermis or sc tissues)
  • frequently affects face, eyelids, lips, tongue
  • Ass/w burning sensation / pain
32
Q

Are chronic urticaria and angioedema due to allergy?

A

Often not! ON Hx: recurring lesions with no obvious temporal relation to allergic trigger.

  • Rx: antihistamines
  • AI disease and other rare disease may need to be excluded
33
Q

What is allergic rhinitis?

A

-Perennial allergens: dust mite, pets, moulds.
-Seasonal allergens: grass pollen
Rx: nasal corticosteroids / antihistamines.
Immunotherapy useful if medical therapy inadequate.

Multisystem (14 decks)

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