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Allergy and Anaphylaxis (Systemic anaphylaxis (Clinical presentation:…

- - - - Mast cell activation: Antigen binds to the adjacent surface of IgEs that are bound to a mast cell. The ab then cross link and signal transduction thru FcRs.
        
        mast cell degranulation resulting in histamine and protease release
        
        activation --> degranulation --> release/production of mediators
        
        Phosphilipase A2 activation -- leads to production of prostaglandins and leukotrienes from AA
        
        prostaglandins can cause bronchospasm and mucus secretions
        -leukotrienes result in powerful spasmogens
        
        result in the immediate response of a type I reaction
        
        What are mast cells?
        
        Mast cells (and basophils) have cytoplasmic membrane bound granules that contain biologically active mediates such as histamine (and others)
        
        if in tissue (mast cell), if circulating (basophil)
        
        How else can mast cells get activated?
        
        Complement anaphylatoxins (C5a/C3a)
        
        Macrophage derived cytokines (IL-8)
        
        Drugs (codeine/morphine, adenosine)
        
        Mellitin (Bee Venom)
        
        Physical Stimuli (Heat, Sunlight, Cold)
        
        Cold Urticaria
        
        If it is a direct mast cell activation without IgE then it's called an anaphylactoid RXN
- - - - Second generation: H1 blockers with no sedating side effects and used for allergy ONLY
      - First generation: H1 blockers (Benadryl)
        
        Sedation-cross blood brain barrier (lipophilic) and anticholinergic
        
        Drug also binds cholinergic, adrenergic or serotonin receptors
        
        BOTH allergy and motion sickness and sleep aid through the blockade of central H1 and muscarinic receptors
- - - - Mast cell mediated: due to allergic or anaphylactoid reactions or ASA conversion
      - Bradykinin-induced due to ACE inhibitor or C1 inhibitor deficiency
        
        Can tell apart by:
        
        there is no urticaria, bronchospasm or allergic sx
        
        there is generally a longer time cousre, the ACE inhibitor induced reaction may be weeks after the medication was started
  - - - intramuscular epinephrine injection:
        
        bronchodilator can help raise BP and increase CO
        
        know the effects of E in different doses
      - Remove inciting antigen, call for resuscitation help and place patient in supine position with lower extremities elevated with supplemental oxygen and volume resuscitation