Anaphylaxis Flashcards
What type of cell causes the symptoms of anaphylaxis?
Mast cells
They are widely distributed in the body in both connective tissue and epithelial mucosa. They contain granule e.g. histamine which are secreted following antigen binding to IgE.
What is the signalling molecule involved?
Histamine and leukotrienes
Histamine causes dilation of vessel and increased permeability so fluid can leaks out causing oedema, It causes constriction of airways and contraction of smooth muscles in the walls of the intestines.
What immunoglobulin class is likely to be involved?
IgE- it is important in parasitic infections however can be inappropriate in terms of allergic reaction, Usually the antigen binds to the surface IgM of lymphocytes and stimulates proliferation. Usually IgM is initially made and switches to different classes, In type 1 hypersensitivity the activation Th2 causes a switch to IgE production
It becomes bound to mast cells and subsequent stimulation cause allergies or anaphylaxis
What causes the rashes and puffy skin?
Vasodilation - Stimulation of connective tissue mast cells causes vasodilation leading to the red colour of the skin rash
Vascular Leakage -oedema leads to its raised appearance.
This type of rash is called urticaria
Why should adrenaline have been given?
Counters the effects of histamine - causes constriction of peripheral vessels and directs blood towards organs
Why did the patient feel faint?
Low blood pressure
Why was blood pressure monitored in hospital?
Good indicator of what’s going on behind the scenes - if it going up then you know the heart is doing well
What are the signs and symptoms of anaphylaxis?
Nausea, abdominal cramps, diarrhea (effects of intestines), runny nose, lightheadedness, confusion, headache, anxiety, swelling of lips/tongue/throat, fast/slow heart rate, low blood pressure, skin (hives, rash, itching), pelvic pain, shortness of breath, hoarseness, wheezes, cough, loss of bladder control
What is anaphylaxis?
An acute type 1 hypersensitive reaction that can be systemic and life threatening
What sorts of drugs might have been in subsequent injections?
Steroid (if it doesn’t settle down)
Different antibiotics
Antihistamines
Bronchodilators
Skin allergies
- Urticaria is used in allergy testing
- Small amounts of possible allergens are injected by pin-prick
- It is then observed to see whether they cause a localised wheal-and-flare reaction
- If the allergen is inhaled, the principal site of action will be mucosal mast cells of the respiratory system.
- If in the nasal passages, this causes oedema in the epithelia lining the nose leading to general irritation including stimulation of mucus secretion. This is allergic rhinitis e.g. hay fever
- If the allergen reaches the bronchioles of the lungs, you get contraction of smooth muscle.
- This decreases the diameter of the airways and causes inflammation and increased mucus production.
- This results in asthma with difficulty breathing in and breathing out.
Food allergies
- If the allergen is ingested it will act at the mucosal mast cells in the intestinal tract.
- Stimulation of associated smooth muscle leads to vomiting and diarrhoea - typical of food allergy
- If the allergic substance can be absorbed and pass into the blood stream, it may also cause skin symptoms (rashes or itching)
Why can anaphlaxis be fatal?
Dilation of vessel causes a dramatic drop in blood pressure which can lead to shock
How does the patient respond to drop in blood pressure?
Increase respiratory (as bronchoconstriction occurs) and heart rate
What is the emergency treatment for anaphylaxis?
- treating hypotension and inflammation
- patient laid down with feet raised to improve blood supply to head and trunk
