ILA Flashcards
Define Anaphylaxis
- Severe, life-threatening, generalised or systemic hypersensitivity reaction which is likely when both of these criteria are met:
- sudden onset and rapid progression of symptoms.
- life-threatening airway and/or breathing and/or circulation problems usually associated with skin and mucosal changes.
Signs/Symptoms of anaphylaxis
- occurs within minutes and lasts 1-2 hrs
- vasodilation
- increased vascular permeability
- bronchoconstriction
- urticaria (hives)
- angio-oedema (rapid, oedema, or swelling, of the area beneath the skin or mucosa)
What is a sign vs symptom?
A symptom is a manifestation of disease apparent to the patient himself, while a sign is a manifestation of disease that the physician perceives.
What is a hypersensitivity reaction?
exaggerated or inappropriate immunologic responses occurring in response to an antigen or allergen.
When would an anaphylactic reaction occur?
when an allergen reacts with a specific IgE antibody on mast cells and basophils (TYPE 1 HYPERSENSITIVITY) - triggers release of histamine and rapid synthesis of newly formed mediators. - can cause capillary leakage, mucosal oedema and ultimately shock and asphyxia (deprivation of oxygen)
what are the most common triggers of anaphylaxis?
-foods: peanuts, pulses, tree nuts (brazil,almond,hazel) , fish, shellfish, eggs, milk, sesame
- venom: bee, wasp
-drugs: abx, opioids, NSAIDs, muscle relaxants (baclofen, diazepam)
-contrast agents: (used in xrays)
how does type 1 hypersensitivity work? (IgE- mediated)
Allergen IgE binds to mast cells with inflammatory mediators released.
clinical manifestations: anaphylaxis, urticaria, angio-edema .
timing: immediate- minutes to hrs.
physiologic responses to the release of anaphylaxis mediators?
-smooth muscle spasm in the respiratory and gi tracts
- vasodilation
- increased vascular permeability
- stimulation of sensory nerve endings
- increased mucous secretion and increased bronchial smooth muscle tone, as well as airway oedema, contribute to the respiratory symptoms observed.
cardiovascular effects result from DESCREASED VASCULAR TONE and capillary leakage.
what is histamine’s role in anaphylaxis?
histamine infusion is enough to cause anaphylaxis symptoms.
it mediates its effects through activation of histamine 1 and histamine 2 receptors.
Vasodilation, hypotension, and flushing are mediated by H1 receptors. H1 receptors alone mediate coronary artery vasoconstriction, tachycardia, vascular permeability, pruritus, bronchospasm, and rhinorrhoea.
H2 receptors increase atrial and ventricular contractility, atrial chronotrophy, and coronary artery vasodilation.
H3 receptors importance in humans is unknown.
underlying pathophysiology of anaphylaxis
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mode of action of anaphylaxis
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algorithm/treatment for anaphylaxis
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Why might a second dose of adrenaline be required?
adrenaline has a short half-life so a second dose might be required if the symptoms aren’t initially responded or get worse.
which confirmatory blood tests do you need to take for anaphylaxis?
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