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Hypersensitivity. Anaphylaxis. Nafiseh Kiamanesh. L earning 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.
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Anaphylaxis Nafiseh 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
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: Foods Peanuts Tree nuts Fish and shellfish Soya products Milk Eggs Insect stings Bee venom Wasp venom Chemicals, drugs and other foreign proteins Penicillin and other antibiotics Intravenous anesthetic agents, e.g. suxamethonium, propofol Latex
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.
