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IgE Mediated Hypersensitivity

ANAPHYLAXIS


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An acute systemic allergic reaction

The result of a re-exposure to an antigen that elicits an IgE

mediated response

Usually caused by a common environmental protein that is

not intrinsically harmful

Often caused by medications, foods, and insect stings

It is a Type I hypersensitivity

WHAT IS ANAPHYLAXIS?


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Foods Peanuts and other legumes,

nuts, eggs, cows milk, shellfish,

seeds, and fruits

Foo

d additivesFoo

d dyesMedications Antibiotics (eg,

penicillin and sulfonamides),

NSAIDs, aspirin, protamine, and

anesthetic agents

Envenomations: Fire ants and

hymeno

ptera, such asbees and wasps

Immunotherapy Allergen extracts

Blood product infusion

Latex

Vaccines

Radiographic contrast media

Idiopathic

Exercise

NSAIDs indicates nonsteroidal anti-inflammatory drugs.

COMMON PEDIATRIC

CAUSES OF ANAPHYLAXIS

Wiener ES, Bajaj L. Diagnosis and emergent management of anaphylaxis in children.Adv

Pediatr. 2005;52:195206


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Anaphylaxis mechanisms and triggers


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Anaphylaxis mechanisms and triggers


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Skin-mucous membrane

involvement

Hives, pruritis, flushing, swollen

lips/tongue/uvula Respiratory compromise

Dyspnea, wheeze, stridor,

hypoxemia

Persistent GI symptoms

Crampyabdominal pain, vomiting

Cardiovascular: BP or symptoms

associated Syncope, incontinence, collapse

SYMPTOMS


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Antigen is presented by

antigen presenting cells

TH2 cells induce B cell

activation

CD40 ligand and cytokines

B cells undergo isotype

switching and produce

antibody Serum antibody is bound by

the mast cells

SENSITIZATION


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Secondary presentation of antigen produces an immediate response controlled

by mast cells

Granule contents are released

Cell mediated response proceeds

THE ALLERGIC RESPONSE


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SENSITIZATION & RESPONSE


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Synthesized and stored in granules

The primary mediator in the granules

3 receptors

H1: Smooth muscle & endothelium

Increased IP3 & DAG

H2: Gastric mucosa, cardiac muscle, mast cells

Increased cAMP

H3: Pre-synaptic brain

Decreases histamine release

HISTAMINE


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Cardiovascular

Decreased blood pressure

Increased heart rateEdema (separation of endothelial cells & increased permeability)

Respiratory

broncho constriction

Gastrointestinal

Smooth muscle contraction and diarrhea

Skin

Urticaria

TISSUE EFFECTS OF HISTAMINE


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Antihistamines

Block H1 and H2 receptors

Epinephrine fo

r bro

ncho

spasmsstimulates the reformation of tight junctions between endothelial cells

IV fluids to support blood pressure

Desensitization

TREATMENTS

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