Anaphylaxis Flashcards
(28 cards)
Define anaphylaxis
A rapidly developing life-threatening airway and/or breathing and/or circulatory problems usually associated with skin and mucosal changes
What are the risk factors for anaphylaxis?
<30 years old for food associated and exercise-induced anaphylaxis
History of atopy or asthma
History of anaphylaxis
Exposure to a common sensitiser e.g. healthcare workers being exposed to latex
Explain the pathophysiology of sensitisation to an allergen
On first exposure to an allergen, the allergen will be picked up by a dendritic cell and presented to a T cell which then stimulates a B cell to produce IgE antibodies against the allergen. These antibodies are released into the bloodstream and bind to. the surface of mast cells and basophils
Describe the pathophysiology of anaphylaxis post-sensitisation
In a sensitised individual, subsequent exposure to an allergen causes allergen binding to IgE antibodies causing degranulation of mast cells and basophils. Histamine from these cells causes blood vessel dilation, increased permeability and smooth muscle contraction. Tryptase acts to break down proteins causing tissue injury. Cytokines attract additional immune cells
Describe the pathophysiology on non-IgE mediated anaphylaxis
Mast cell and basophil degranulation is stimulated directly without the involvement of IgE
This could be immune mediated e.g. some blood products can bind to circulating antigens to form immune complexes which activate complement proteins which triggers mast cell degranulation
Contrast medium and opioids can cause direct non-immune mediated degranulation
How does anaphylaxis cause shock?
Immune mediators depress myocardial function directly, cause vasodilation and cause leakage of fluid from capillary blood vessels into the extra-vascular compartment
How does anaphylaxis cause airway obstruction?
Fluid leaks from the capillary blood vessels and causes tissue swelling
Altered smooth muscle tone results in bronchospasm and asthma
Food allergens are some of the most common causes of anaphylaxis. Which foods are common allergens?
Egg Milk Peanuts Nuts Fish and Shellfish
Anaphylaxis caused by food allergens is most common in what age group?
Children
Drug-induced anaphylaxis is most common in what age group?
Adults
What is meant by food-associated exercise-induced anaphylaxis?
Anaphylaxis occurs when a patient exercises within 2-4 hours of ingestion of a specific food
Which drugs most commonly cause anaphylaxis?
Penicillins
NSAIDs
Contrast Media
Opiates
List common triggers of anaphylaxis?
Food - eggs, milk, peanuts, nuts, fish and shellfish
Latex
Drugs - NSAIDs, penicillins, radio-contrast media, opiates
Bites and stings - spider, wasps, ant, bees
Exercise
Idiopathic
Seminal fluid
What are the 3 criteria for the diagnosis of anaphylaxis?
Sudden onset and rapid progression of symptoms usually developing over minutes
Life threatening airway, breathing or circulation problems
Usually also skin / mucosal changes present
What findings of anaphylaxis may be found on assessment of a patient’s airway?
Throat and tongue swelling with difficulty breathing and swallowing
Hoarse voice
Stridor
What findings of anaphylaxis may be found on assessment of a patient’s breathing?
Increased respiratory rate Wheeze Confusion caused by hypoxia Patient feels tired Cyanosis Respiratory arrest
What findings of anaphylaxis may be found on assessment of a patient’s circulation?
Signs of shock - blue cold peripheries, CRT >3. secs, veins undefiled or collapsed due to hypovolaemia, tachycardia, blood pressure normal or low, reduced level of consciousness
Low blood pressure with feeling of fairness / dizziness or collapse
Chest pain with ECG changes
Bradycardia and cardiac arrest
What findings of anaphylaxis may be found on assessment of disability in a patient?
Airway, breathing and circulatory problems can affect neurological status leading to confusion, agitation and loss of consciousness
GI symptoms - abdominal pain, nausea, vomiting and incontinence
What findings of anaphylaxis may be found on assessment of exposure in a patient?
Skin / mucosal changes are often the first presenting feature
Erythema and urticaria
Angio-oedema, swelling of the deeper tissues including eyelids, lips, mouth and throat
In which patients with anaphylaxis should a mast cell tryptase test be used?
Patients aged 16+
Patients aged <16 if trigger is not food-related
Ideally 3 mast cell tryptase measurements should be taken for patients in anaphylaxis. When should each of these measurements be taken?
One as soon as possible after resuscitation
One 1-2 hours after the start of symptoms
24 later to act as a baseline
What investigations should be used for patients with anaphylaxis?
Mast cell tryptase 12-lead ECG U&Es ABGs CXR
What is the immediate management of anaphylaxis?
IM adrenaline and removal of the trigger
Supportive management with 15L oxygen on. trauma mask, IV fluid challenge
How. should the patient be positioned in anaphylaxis?
Lie down, legs up
