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Hypersensitivity Concepts Vo



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  • 1. Peggy D. Johndrow 2009
  • 2. Hypersensitivities/Allergies
    • Increased or excessive response to presence of antigen to which client has been exposed
    • Degree of reaction ranging from uncomfortable to life threatening
    • Terms hypersensitivity and allergy used interchangeably
  • 3. Type I: Rapid Hypersensitivity Reactions
    • Also called atopic allergy: most common type of hypersensitivity
    • Some reactions occur only in areas exposed to antigen
    • Allergens contacted:
      • Inhaled (plant pollens, fungal spores, animal dander, house dust, grass, ragweed)
      • Ingested (foods, food additives, drugs)
      • Injected (bee venom, drugs, biologic substances)
      • Contacted (pollens, foods, environmental proteins)
    • Related to increased production of IgE
    • Examples: h ay fever, allergic rhinitis, allergic asthma, anaphylaxis, & allergies to certain foods &/or medications
    • Anaphylaxis : severe reaction, involve all blood vessels and bronchiolar smooth muscle, causing widespread blood vessel dilation, decreased cardiac output, and bronchoconstriction
    • IW Table 22-1 p 388
  • 4. Allergic Rhinitis
    • Triggered by reaction to airborne allergens
    • Seasonal: coincides with timing of environmental exposure (i.e. spring) & lasts a short time
    • Chronic: occurs intermittently without seasonal pattern or continuously when exposed to certain allergens
    • Pathophysiology: initial exposure body responds by making antigen specific IgE which bind to surface of basophils & mast cells
    • Repeat exposure to allergen results in two phase response
      • Primary: allergen binds to IgE molecules; cell degranulates, histamine released resulting in capillary leak, mucous secretion, pruritis, & erythema
      • Secondary: additional proteins released, increased WBC’s; more generalized reaction occurs
  • 5. Assessment
    • History: onset & duration symptoms: family history
    • Clinical Manifestations: rhinorrhea, itchy/watery eyes, H/A, swollen nasal mucosa, post nasal drip, dry/scratchy throat & pharyngitis
    • Diagnostic studies
      • CBC: increased eosinophil count (1-2%)
        • IgE indicates tendency to have allergic responses (>100 IU/mL)
      • RAST: determines specific allergies by determining blood level of IgE against certain allergen
      • Skin testing
        • Immediate hypersensitivity reaction occurs in 15 min’ positive = redness & wheal
        • Instruct client to stop systemic glucocorticoids & antihistamines 5 days prior to procedure
        • Emergency equipment available
      • Intradermal testing
        • Performed if a specific allergen did not produce a reaction
      • Oral food challenge
        • Used to identify specific allergens when skin testing or food diary fails
    • IW Table 22-2 p 391
  • 6. Latex Allergy
    • Allergic reaction to a protein found in processed natural latex
    • Signs and symptoms vary in range (immediate to delayed)
    • Increased risk for allergy seen with high exposure to latex, spina bifida, allergy to bananas or avocados
    • Management
      • Ask all clients about use & known reaction to latex, or specific food allergies
      • Utilize latex free products in care of client
  • 7. Management
    • History
    • Physical assessment/clinical manifestations
    • Laboratory assessment
    • Allergy testing including skin testing, scratch testing, intradermal testing, oral food challenge
    • Avoidance therapy, symptomatic therapy, pharmacotherapy
    • IW Chart 22-1 p 390
  • 8. Pharmacotherapy
    • Decongestant: cause vasoconstriction of inflamed tissue
      • Examples: Neo-synepherine, Afrin
    • Antihistamines: block histamine from binding to receptor site, prevents vasodilatation & capillary leak
      • Examples: Benadryl, Chlor-trimeton, Zrytec, Clarinex, Allegra
    • Corticosteroids: decrease inflammation & immune response
      • Examples: Prednisone, Delta-cortef, Beconase, Flonase
    • Mast cell stabilizers: prevent mast cell membrane from opening when allergen binds to IgE
      • Example: Nasacrom
    • Leukotriene antagonics: blocks leukotriene receptor & prevents synthesis
      • Examples: Accolate, Zyflo, Singulair
    • Complementary and alternative therapy
    • (IW Chart 22-3 p 393)
  • 9. Avoidance and Desensitization Therapy
    • Avoidance therapy
      • Instruct client to avoid direct or close contact w/ known allergens
    • Desensitization therapy
      • Used when identified allergens can't be easily avoided
      • Decrease allergic response by competition
  • 10. Anaphylaxis
    • Systemic reaction; occurs rapidly after exposure (in seconds)
    • Initial feelings of uneasiness, apprehension, weakness & impending doom
    • Pruritus & urticaria
    • Erythema and sometimes angioedema eyes, lips, tongue
    • Histamine causes capillary leak bronchoconstriction, mucosal edema & excess mucus secretion
    • Congestion, rhinorrhea, dyspnea & increasing respiratory distress with audible wheezing result
    • Potentially fatal
    • IW Chart 22-2 p 392
  • 11. Cascade
    • Itching, urticaria  angioedema  dyspnea, increased salivation, audible wheezing  laryngeal edema, stridor, hypoxia  hypotension, dysrhythmias, shock  cardiopulmonary arrest
  • 12. Interventions
    • Initially assess respiratory function; must always establish and maintain an airway
    • Prepare for emergency intubation or tracheostomy
    • Oxygen reduces hypoxemia: O2 via NC 2 2-6L/min to maintain SAO2 >90%
    • Pharmacotherapy: (IW Chart 22-3 p 393)
      • Epinephrine (1:1000) .03-0.5 mL SQ; with initial symptoms
      • Antihistamines (25-100mg) IM, IV or PO; treat angioedema & urticaria
      • Theophylline (6mg/kg) IV over 20-30 min: bronchodilator
      • Inhaled beta-adrenergic agonist via small volume (high flow) nebulizer Q2-4 hrs; bronchodilator
      • Corticosteroids; decrease inflammation
      • Dopamine, Levophed; increase B/P
    • May require CPR
  • 13. Type II: Cytotoxic Reactions
    • Body makes special autoantibodies directed against self cells that have some form of foreign protein attached
    • Clinical examples include hemolytic anemias, thrombocytopenic purpura, hemolytic transfusion reactions, Goodpasture’s syndrome, and drug-induced hemolytic anemia
    • Management
      • D/C medication or blood product
      • Hemolytic crisis or renal failure can occur
      • Treatment usually symptomatic
        • May require plasmapheresis
  • 14. Type III: Immune Complex Reactions
    • Excess antigens cause immune complexes to form in blood; these circulating complexes usually lodge in small blood vessels
    • Usual sites include kidneys, skin, joints & small blood vessels
      • Lodge in the small vessel walls, trigger inflammation & cause tissue or vessel damage
    • Deposited complexes trigger inflammation, resulting in tissue or vessel damage
    • Examples: rheumatoid arthritis, systemic lupus erythematosus & serum sickness
    • IW Table 22-3 & Women Health p 396
  • 15. Type IV: Delayed Hypersensitivity Reactions
    • Reactive cell T-lymphocyte (T-cell)
    • Antibodies & complement not involved
    • Local collection of lymphocytes & macrophages causes edema, induration, ischemia & tissue damage at site within hours to days after exposure
    • Examples: Tb test (positive purified protein derivative), contact dermatitis, poison ivy skin rashes, insect stings, tissue transplant rejection & sarcoidosis
  • 16. Management
    • Intervention
    • Identification and removal of allergen
    • Client preparation
    • Procedure
    • Follow-up care
    • Reaction self-limiting & treated symptomatically
  • 17. Type V: Stimulatory Reactions
    • Inappropriate stimulation of a normal cell surface receptor by an autoantibody, resulting in a continuous “turned-on” state for the cell
    • Example: Graves’ disease, form of hyperthyroidism
      • IW Table 22-3 p 396
    • Management
      • One organ: removal of enough tissue to return function to normal
      • Widespread involvement: decrease autoantibody production with immunosupression
  • 18. Sjögren’s Syndrome
    • Group of problems often appear with other autoimmune disorders
    • Dry eyes, dry mucous membranes of nose/mouth (xerostomia) & vaginal dryness
    • Insufficient tears causing inflammation & ulceration of cornea
    • Treatment: immunomodulation & symptomatic therapy
  • 19. Goodpasture’s Syndrome
    • Autoimmune disorder in which autoantibodies made against glomerular basement membrane & neutrophils
    • Lungs and kidneys
    • Shortness of breath, hemoptysis, decreased urine output, weight gain, edema, hypertension & tachycardia
    • Treatment: high-dose corticosteroids
  • 20. Therapies
    • Pharmacotherapy:
      • Rheumatrex (methotrexate)
      • Cytoxan (cyclophosphamide)
      • Corticosteroids
      • Sandimmune (cyclosporine)
      • Plaquenil (hydroxchloroquine)
    • Symptomatic
      • Artificial tears, saliva
      • Lubricants
      • Pain control
    • Renal support: hemodialysis, peritoneal dialysis
    • Other
      • Plasmapheresis (filter plasma, remove proteins)