Hypersensitivity

AnaphylaxisNafiseh Kiamanesh

Learning Objectives

• Knowledge of the mechanism which causes anaphylaxis and the agents which are most likely to cause it;

• be able to recognize the signs and symptoms of anaphylaxis;

• Understand how to treat anaphylaxis

Lecture Objectives • Definition

• Introduction

• Epidemiology

• Pathophysiology

• Aetiology

• Diagnosis

• Treatment

• Prevention

What is anaphylaxis?• Ana (without); phylaxis (protection / guard)• An acute systemic allergic reaction• Life-threatening • 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• True vs. pseudo anaphylaxis

4 Types of Hypersensitivity

• Type I : Mediated by IgE

• Type II : Mediated by anti-tissue Ab IgG and IgM

• Type III : Mediated by immune complexes

• Type IV : Cell-mediated immune complexes

History

Richet & Portier

Epidemiology

• Underreported

• 50/100 000 p/yr

• No known geographic, racial, or sex predilection

• 1-15% at risk every year

• 1500 deaths p/yr

• Global increasing rates

Pathophysiology

Pseudoanaphylaxis

• Anaphylactoid Reactions are caused by activation of mast cells and release of the same mediators, but without the involvement of IgE antibodies.

• Management is similar to anaphylaxis.

Primary Symptoms

• Time to onset is variable, but symptoms usually occur within seconds to minutes of exposure to the offending antigen.

CUTANEOUS• Swelling (angio-oedema(• Urticaria• Redness (erythema)• Itching (pruritus)

RESPIRATORY Wheezing Dyspnoea Rhinitis Laryngeal obstruction

causing stridor Hypoxia

Secondary Symptoms

GASTROINTESTINAL Nausea Diarrhoea Abdominal Pain Vomiting

CENTRAL NERVOUS SYSTEM• Confusion• Feeling of impending doom• Apprehension• Metallic Taste• Altered levels of consciousness

CARIOVASCULAR Hypotension Tachycardia Arrhythmias

Death

• Death is usually attributable to asphyxiation from upper airway edema and congestion, irreversible shock, or a combination of these factors. Death may occur after many hours of shock from the effects of the failure of other organs.

ANAPHYLAXIS

Causes Anaphylaxis:FoodsPeanutsTree nutsFish and shellfishSoya productsMilkEggsInsect stings Bee venomWasp venomChemicals, drugs and other foreign proteins Penicillin and other antibioticsIntravenous anesthetic agents, e.g. suxamethonium, propofolLatex

Causes

Anaphylactoid:•Opiates•Aspirin•Radio contrast media•Physical Exercise•Cold

Idiopathic:

No cause can be identified in 30% of patients with anaphylaxis

Note

Any protein is a potential

allergen, which may cause an

anaphylactic reaction

Treatment• Serum tryptase remains elevated for up to 6 hours

• Immediate treatment with epinephrine

• Anti-histamine

• Others:

Corticosteroids

β2 agonist (inhaled)

Glucagon

IV fluids

Supplemental oxygen

prevention

• Avoidance of offending antigen, where possible; skin testing and desensitization to materials such as penicillin and Hymenoptera venom, if necessary.

• Individuals should wear an informational bracelet and have immediate access to an unexpired epinephrine kit.

Epi-pen

Questions