Anaphylaxis

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Author:
jknell
ID:
198191
Filename:
Anaphylaxis
Updated:
2013-02-06 17:38:18
Tags:
Pulm II
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Description:
Lecture on anaphylaxis
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  1. Anaphylactic and atopic
    • Hypersensitivity type I reactions
    • antibody mediated
    • - free antigen crosslinks IgE on pre-sensitized mast cells and basophils, triggering release of vasoactive amines that act at postcapillary venules (i.e. histamine).

    -Reaction develops rapidly after antigen exposure because of preformed antibody

    "First (type) and Fast (anaphylaxis)"
  2. Anaphylaxis
    clinical manifestations
    Acute onset (minutes to hours)... [type 1 to type 3 (mild to severe)]

    -Cutaneous - flush 46%, urticaria/angioedema 88% (less common with ingested allergens)

    -Respiratory - upper vs. lower airway (upper airway edema 56%) (dyspnea/wheeze 47%)

    -Cardiovascular - BP (hypotension 10-30%), ECG, collapse.

    -GI - 30%

    -Other - metallic taste (response to histamine in the blood), impending doom
  3. Anaphylaxis
    Pathophysiology
    • CV:
    • -Decline in LV systolic function is closely associated with histamine in the blood
    • -Decrease blood volume: loss of fluid (plasma) into interstitial space
    • -- Hct appears to go up...

    • Heart rate increases
  4. Anaphylaxis
    pathology
    • Airway edema
    • Pulmonary hyperinflation
    • Myocardial ischemia
    • Visceral congestion
    • Eosinophilic inflammation
    • Laryngeal edema
  5. Anaphylaxis
    Dx and Ddx
    • Dx:
    • -history
    • -physical exam
    • -serum tryptase or carboxypeptidase levels (some individuals have elevated baseline of tryptase, predisposed to anaphylaxis)
    • -Skin testing
    • -In vitro testing

    • Ddx:
    • -Aspiration
    • -Myocardial infarction
    • -Cardiac arrythmia
    • -Seizure
    • -Pulmonary embolism
    • -Vasovagal syncope - pt will have slow heart rate
    • -Functional disorders - pt will intentionally ingest a known allergen (or by proxy)
  6. Anaphylaxis
    Etiology
    • -IgE mediated
    • Foods, drugs, venoms, foreign proteins, therapeudic extracts, environmental allergens (rare), Exercise + food

    • -Non-IgE mediated
    •       -Complement induced - radiocontrast media (rcm), transfusion reaction
    •       -Direct mast cell activation - rcm, opiates
    •       -Arachidonic acid associated - NSAIDs

    -Idiopathic
  7. Anaphylaxis
    Risk factors
    • Atopy - especially for food induced
    • Exposure - occupation, medical procedure
    • Mast cell disease - mastocytosis, mast cell release syndrome
    • PAF hydrolase deficiency
  8. Food induced anaphylaxis
    Allergen - glycoproteins, acid resistant

    • Children: milk, egg, peanut, soy
    • Adults: nuts, peanuts, fish, shellfish

    Fatalities are often associated with asthma, late use of adrenalin, peanuts
  9. Anaphylaxis
    Skin testing 
    • Selecting patients:
    • -history suggests IgE mediated process
    • -reaction to stings (hymenoptera rxn)
    • -Abx reaction
    • -Food reaction
    • -Patient not tolerating or responding to anti-allergic medication

    • Testing:
    • -Epicutaneous - prick puncture; look for wheal and flare. Only test for inhalant allergens. Size of reaction does NOT correlate to severity of anaphylaxis
    • -Intradermal - Large volume of dilute allergen, best for drugs and hymenoptera
  10. In vitro allergy testing
    • Pt selection:
    • -strong suspect of allergic rxn - especially foods
    • -Skin testing unavailable, contraindicated, or negative result (with strong suspicion)
    • -dermatographism
    • -pt taking anti-histaminic drug

    • Testing:
    • radio-allergo-sorbent test
  11. Anaphylaxis in surgery
    • Muscle relaxant--#1 in Europe
    • Opiate
    • Antibiotic --#1 in US
    • Latex
    • Induction agent
    • Plasma expander
    • Protamine
  12. Latex allergy
    Exposure - gloves, surgical supplies, balloons, condoms

    Incidence - 1-% of operative anaphylaxis

    Risk factors - atopy, food allergy, multiple surgeries, spina bifida
  13. Anaphylaxis treatment
    • Acute:
    • -Epinephrine - IM (not sub-Q)
    • -B2 agonist
    • -Corticosteroids - no studies to indicate their efficacy
    • -Methylxanthines
    • -Antihistamine - no studies to indicate their efficacy
    • -Glucagon - reverses beta blockade; pts often vomit
    • -Vasopressin

    • Longterm:
    • -Desensitization - must continue using the drug for effect to last
    • -Immunotherapy - long term therapy; primarily for venoms
    • -Drug intervention: (prophylaxis, active acute therapy)

    • ...
    • -Avoid exposure
    • -provide epinephrine

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