Lecture notes on hypersensitivity reactions PDF

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LECTURE NOTESAssessment and Management of Patients with Allergic DisordersHypersensitivity/ allergy- Inappropriate or exaggerated responses to specific antigens.  An inappropriate and often harmful response of the immune system to normally harmless substance called allergens (e., dust, weeds, poll...

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LECTURE NOTES Assessment and Management of Patients with Allergic Disorders Hypersensitivity/ allergy      

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Inappropriate or exaggerated responses to specific antigens. An inappropriate and often harmful response of the immune system to normally harmless substance called allergens (e.g., dust, weeds, pollen, dander) Antigens from these allergens are recognize by the body’s immune system as foreign, and as a response, lymphocytes produce antibodies in an attempt to remove or destroy them. Immunoglobulins—antibodies that are produced by lymphocytes and plasma cells in response an immunogenic stimulus. (GAMED—IgG, IgA, IgM, IgE, IgD) IgE- Immunoglobulins involved in allergic disorders and some parasitic infection. Two or more molecules of Ige bind to an allergen stimulates mast cells to release chemical mediators. Chemical Medicators- released in allergic reaction produce symptoms that range from mild to life-threatening. 2 types of chemical Mediators 1. Primary- Preformed and found in mast cells or basophils. o Histamine- effects are greatest about 15 minutes after antigen contact. Causes erythema, localized edema (wheals), pruritus, wheezing, bronchospasm, increased secretion of gastric and mucosal cells resulting into diarrhea. (H1 receptors- found in bronchial and vascular muscle cells; H2 receptor- found on gastric parietal. o Eosinophil chemotactic factor of anaphylaxis (ECF-A)- attracts eosinophils to the site of allergen. o Platelet-activating factor (PAF)—initiates plate aggregation and leukocyte infiltration at site of immediate hypersensitivity reaction. o Prostaglandin- produces smooth muscle contraction as well as vasodilation and increased capillary permeability. May cause fever and pain which occur with inflammation. 2. Secondary Mediators- inactive precursors formed or released in response to primary mediators o Bradykinin- increase vascular permeability resulting to edema; vasodilation, hypotension and contraction of smooth muscles such as bronchi. It also stimulates nerve cell fibers and produces pain. o Leukotrienes- initiate inflammatory response. Also causes bronchial contraction, mucus secretions in airway and typical “wheal-and-flare reaction of the skin. First exposure to the allergen/antigen causes Sensitization and may not cause allergic reactions. Allergic reaction takes place after re-exposure of a pre-disposed person.

Type I Hypersensitivity      

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Also called Immediate Hypersensitivity and IgE-mediated reaction also called anaphylactic hypersensitivity May include both local and systemic hypersensitivity- (allergic rhinitis, asthma, penicillin allergy, latex allergy) Rapid onset- 5-30 minutes after exposure to allergen occurs when allergens bind to IgE on surface of mast cells with consequent release of several mediators begins when an antigen induces the formation of IgE antibody

Anaphylaxis- most severe allergic reaction. Characterized by edema in many tissues, including larynx, accompanied by hypotension, bronchospasm and cardiovascular collapse. Onset of symptoms begins first 2 hours after exposure. Mild S/s: nasal congestion, periorbital swelling, pruritus, sneezing, tearing of the eyes. Moderate s/s: flushing, warmth, anxiety, itching in addition to the mild symptoms. Bronchospasm, edema of airways or larynx, dyspnea, cough, sweating. Severe S/s: laryngeal edema, bronchospasm, dysphagia, abdominal cramping, vomiting, diarrhea, seizures, cardiac arrest and coma. Common causes of anaphylaxis -- Food (peanut, shellfish, fish, milk, eggs, soy, wheat)

-- Medications (antibiotics specially penicillin, allopurinol, radiocontrast agents, anesthetic agents like lidocaine, vaccines, hormones like insulin and vasopressin, aspirin, NSAID’s) -- Animal Serum -- Insect stings -- latex 

Prevention -- Avoid potential allergens -- if at risk for anaphylaxis, avoid areas populated by insects. -- use proper clothing, and insect repellents -- Carry and administer epinephrine in the event of exposure to allergen -- EpiPen—commercially available first aid device that delivers pre-measured dosage of 0.3 mg or 0.15 mg of epinephrine.

Management      

Evaluation of respiratory and cardiovascular functions If (+) cardiac arrest—CPR Epinephrine is administered in a 1:1000 dilution through SQ and followed by continuous IV infusion Antihistamine Corticosteroids IV fluids (PNSS), volume expanders, vasopressor agents

Nursing Management:   

Assess signs and symptoms of anaphylaxis Prepare initiation of emergency measures (intubation, emergency medications, IV lines, fluid administration, oxygen Health Teaching—Prevention of another anaphylaxis, administration of emergency medications , prevention of antigens

Allergic Rhinitis (hay fever, seasonal allergic rhinitis)    

Most common form of respiratory allergy Classified under type 1 hypersensitivity Demonstrate seasonal variation (common during early spring, early summer and early fall) Induced by airborne pollens or molds...