ANAPHYLAXIS

Fatima Al-Awadh

Objectives

Define Hypersensitivity Reaction. Mention the Types of Hypersensitivity

Reactions. Define Anaphylaxis. Mention the Etiologic Causes. Explain the Pathophysiologic Mechanism. Mention the Signs & Symptoms. Demonstrate the Diagnostic

Investigations. Display the Treatment & First Aid.

Hypersensitivity Reaction

Injurious, or pathologic, immune reactions are called hypersensitivity reactions.

Hypersensitivity reactions may occur in two situations.

First, responses to foreign antigens may be dysregulated or uncontrolled, resulting in tissue injury.

Second, the immune responses may be directed against self antigens, as a result of the failure of self-tolerance (autoimmunity).

Types of hyper sensitivity reactions

Mast cell release

histamine and other mediators

Immediate hypersensitivi

ty

Antibodies directed against cell or tissue

antigens

Antibody-mediated

Antibody-antigen complex

deposit in blood

vessels

immune complex diseases

Reactions

of T lymphocyt

es

T cell-mediated diseases

Anaphylaxis

Ana (without), phylaxis (protection).

Acute multi-systemic allergic reaction involving the skin, airway, vascular system, and GI.

Sever immediate (type I) hypersensitivity reaction.

True & pseudo-anaphylaxis.

Etiology

34%

37%

20%

7%

2%

Causes of anaphylaxis in a study of 266 patients (Data from Kemp et al)

Food

Idiopathic

Drugs

Exercise

Latex, hormons, insect bites

Etiology

Pharmlogic agents• Antibiotics (penicillin)• Nonsteroidal anti-inflammatory drugs (Asprin)• intravenous (IV) contrast agents

Stinging insects• Ants, bees, hornets, wasps, and yellow jackets.

Food• Peanuts, seafood, and wheat

Latex• Rare• No latex-associated deaths

Pathophysiology

First exposure Activation of TH2 cell → Stimulate IgE switiching

Allergen

TH2 Cell B Cell

Pathophysiology

First exposure IgE production

IgE secreting B cellIgE

Pathophysiology

First exposure IgE bind to mast cell

Mast cellFcɛRIIgE

Pathophysiology

Second exposure Recognition Allergen

Mast cell

FcɛRIIgE

Pathophysiology

Second exposure Activation of mast cell to release

histamine and other mediatorsAllergen

Mediators

Mast cell

FcɛRIIgE

Pathophysiology

Mediators

Vascoactive aminase & lipid

Immediate hypersensitivity

reaction (minutes)

Cytokines

Late phase reaction (6-24 hours)

Signs & Symptoms

Itching flushing

hives (urticaria) swelling

Skin

Signs & Symptoms

Itching tearing

redness swelling around the eyes

Eyes

Signs & Symptoms

Sneezingrunny nose nasal congestion

swelling of the tongue metallic taste

Nose & mouth

Signs & Symptoms

Difficulty breathing coughing chest tightness wheezing or other

sounds

increased mucus production

throat swelling or itching change in voice or a sensation of

choking

Lungs and throat

Signs & Symptoms

Dizziness weakness fainting

rapid, slow, or irregular heart rate low blood pressure

Heart and circulation

Signs & Symptoms

Nausea vomiting

cramps diarrhea

Digestive system

Signs & symptoms

Anxiety confusion

sense of impending doom

Nervous system

Diagnosis

The diagnosis of anaphylaxis is based upon symptoms that occur suddenly after being exposed to a potential trigger.

Differential diagnosis severe asthma attack heart attack panic attack food poisoning An increased amount of tryptase protein can be

measured in a blood sample collected during the first three hours after anaphylaxis symptoms have begun.

tryptase levels are seldom elevated in food-induced anaphylaxis

First Aid

Place patient in Trendelenburg position.

Establish and maintain airway.

Give oxygen via nasal cannula as needed.

Place a tourniquet above the reaction site.

Epinephrine at the site of antigen injection.

Start IV to rise BP.

Treatment

EPINEPHRINE Benadryl (diphenhydramine) - H1

antagonist Tagamet (cimetidine) - H2 antagonist Corticosteroid therapy In severe anaphylaxis, observe for 6

hours or longer

Prevention

Avoid the responsible allergen (e.g. food, drug, latex, etc.).

Keep an adrenaline kit (e.g. Epipen) and Benadryl on hand at

all times.

Wear medic Alert bracelets .

Venom immunotherapy is highly effective in protecting insect-

allergic individuals.

References

Abbas & Lichtman, Basic Immunology 3E, Chapter 11 http://www.authorstream.com/Presentation/Moiloa-898248-

anaphylaxis/ http://med.mui.ac.ir/clinical/orjanc/Anaphylaxis.ppt http://

www.uptodate.com/contents/anaphylaxis-symptoms-and-diagnosis-beyond-the-basics

http://www.oregonems.org/Downloads/Anaphylaxis.ppt

Fatima Al-Awadh

Thank You