Anaphylaxis - PDF

Building SCHEMATA with Anaphylaxis Slides Anaphylaxis Life-threatening allergic reaction that effects Airway, Breathing, Circulation =/- skin symptoms - Anaphylaxis is a life-threatening generalised or systemic hypersensitivity reaction.  Some people are more susceptible (Certain genes/...

Building SCHEMATA with Anaphylaxis Slides Anaphylaxis Life-threatening allergic reaction that effects Airway, Breathing, Circulation =/- skin symptoms - Anaphylaxis is a life-threatening generalised or systemic hypersensitivity reaction.  Some people are more susceptible (Certain genes/environmental exposure) Slide 4 (Meanings of words) 1. Urticaria: Also known as hives (Red itchy bumps with rash) 2. Angioedema: Swelling under the skin surface 3. Objective Dyspnoea: Gasping (Increased respiratory rate/decreased 02 saturation/use of accessory muscles) Grade 1: Local Reaction: on skin-but no changed vital signs Grade 2 (a)[Mild/moderate] Skin or GI tract (like vomiting & Diarrhoea) Grade 2 (b): [Mild/moderate] Skin and GI tract (Like vomiting & Diarrhoea) Grade 3 (a): [Severe] Respiratory or Cardiovascular (Like BP/tachy) Grade 3 (b): [Severe] Severe respiratory and/or Severe cardiovascular Grade 3 C: [SEVERE] Respiratory arrest and/or Cardiovascular arrest Intolerances and Allergies Intolerance and allergy are used interchangeably. Intolerance is an adverse reaction to a substance such as; a food group, lactose or gluten. Although symptoms experienced can be unpleasant and make an individual feel extremely unwell it is not life threatening. Reactions to intolerances are usually delayed, occurring several hours and sometimes up to several days after ingestion. Building SCHEMATA with Anaphylaxis Slides The immune system recognise allergens as a threat and therefore produces an inappropriate response such as localized itching. In more severe cases, can cause anaphylaxis. Allergic reactions happen quite quickly within a few minutes of exposure to the allergen. Symptoms of intolerances and allergies can be reduced by avoiding exposure to the allergen. Anaphylaxis is: 1. Severe reaction 2. Generalised (rash might be on 1 area/might only effect respiratory) 3. Or Systemic (effects all systems) Pathophysiology of anaphylaxis: 1. Person is exposed to the allergen (sometime the reaction mirrors the method in which the allergen is introduced into the body, like something inhaled might cause respiratory issues). 2. On initial exposure of allergen, B-lymphocytes produce antibodies- immunoglobulin E (IgE). 3. These bind to first to mast cells (these are immune cells to protect us from harmful allergens) and later to basophils (white blood cells that help us fight infections) which have IgE receptors. 4. On subsequent exposure of the same allergen– immunoglobulin E (IgE) – is raised. 5. On binding with mast cells, various chemical mediators (kick-starters); also known as degranulation (Think of various granules that come out from these protective cells as a response) are released. 6. So which chemicals are released?? Firstly, from the mast cells- a massive amount of histamine is released-this can kick-start systemic effects, like vasodilation (so rapid drop in BP). Remember drop in BP= loss of consciousness/collapse. Building SCHEMATA with Anaphylaxis Slides Thinking of the BP formula-the effect is on the systemic vascular resistance (Cardiac output x Systemic Vascular Resistance= BP). But vasodilation also means that the blood with the allergen is closer to the skin-that’s why the rash/irritation. Histamine can also have dramatic effects on the airway binding to histamine receptors in the smooth-muscle layers of the bronchial tree, causing bronchoconstriction and stimulating increased mucus production from goblet cells in the respiratory mucosa. 7. During anaphylaxis- platelet-activating factor (PAF) is also released from platelets (and basophils)-this breaks down endothelial cells, so with histamine as well-both massively increase vascular permeability- remember this means fluid will leak out and hence why the swelling. 8. Mast cells also produce Prostaglandin D2-found in brain too. These are produced during inflammation-but this causes both bronchoconstriction and vasodilation. So patient will get swelling in airway-need to quickly intubate before this happens. THINK!! That’s why we give a lower dose of adrenaline-Beta2 effect (to broncho-dilate). 500mcg REMEMBER IM (Intra-muscular) 9. Urticarial (like hives) rash: During later stages – immunoglobulin E (IgE) bind to basophils (white blood cells in bone marrow that help us fight infections) which have IgE receptors. These enter the circulation as mature cells, and penetrate different tissues presenting urticarial rash. Refractory Anaphylaxis: This when 2 doses of IM adrenaline were give but respiratory and cardiovascular problems still present. This algorithm is slightly different: It involves giving broncho-dilators (like salbutamol/nebulisers- Fluid therapy- repeated doses of adrenaline until adrenaline infusion up. Adrenaline: From the slide, you might be wondering that if the adrenaline is given at a low dose for broncho-dilation (Beta effect), then how is it also causing vasoconstriction (alpha effect)?? By acting on the heart contractility and rate (cardiac output), the BETA (mainly) helps to restore the BP, but despite mainly having a BETA effect, it still has some ALPHA effect which acts on vessels. Likewise, a higher dose of adrenaline (or Building SCHEMATA with Anaphylaxis Slides noradrenaline) has more ALPHA effect but still has some BETA. Plus, if you think about it-the broncho-dilation needs to be sorted first. See this for more details. Adrenaline in the Acute Treatment of Anaphylaxis - PMC (nih.gov) Key words in a sequence: immunoglobulin E (IgE): Lots of antibodies released from exposure to allergen mast cells: IgE binds to mast cells-cos they have IgE receptors Degranulation: Mast cells through out various chemicals Histamine: Chemical involved in immune response platelet-activating factor (PAF): released from platelets-causes vascular permeability. Vascular Permeability: Leakage of fluid out of vessels Prostaglandin D2: produced by mast cell during inflammation-also helps histamine in broncho-constriction. Basophils: white blood cells- Found in bone marrow-released to fight infections/toxins.