Anaphylaxis and allergies Flashcards
Recap Immune System
Plasma cells produce antibodies following stimulation from b cells and helper t cells.
Antibodies tag antigens so that phagocytes can identify and destroy quicker. Adhere to surface as a clump to prevent antigens from functioning.
what is an allergy
abnormally powerful immune response to an antigen that usually poses no threat to the body.
groups for allergic triggers
Ingestibles, food and drink
Venom
Chemicals, hair dye, latex
Drugs
difference between allergy and anaphylaxis
allergy=single system response
anaphylaxis = multi system response usually involving respiratory and circulatory systems
anaphylaxis definition
a severe, life-threatening, generalised or systemic hypersensitivity reaction.
general characterisations of anaphylaxis
airway problems
breathing problems
circulatory problems
usually skin or mucousal changes
what antibody causes the majority of allergies
Immunoglobin E IgE
which exposure causes anaphylaxis and why
second exposure causes anaphylaxis. first exposure is a slower, smaller reaction while second exposure is faster and more extreme due to memory cells and antibodies in the bloodstream
anaphylactic pathophysiology
Antigen presence triggers release of IgE antbodies
IgE antibdoies bind to surface of mast cell or basophil (granulocytes)
Subsequent exposure to allergen with antigen present
antigens bind to IgE antibodies on mast cells and basophils causing degranulation to occur
this is the release of histamine and other response mediators
Bodies reactions to histamine
Dilation of blood vessels
Bronchoconstriction
Increased permeability of blood vessels
Adrenaline released
Swelling and inflammation
rapid heartbeat
blood clots
gastric acid secretion
Patient assessment: airway anaphylaxis
Angioedema larynx and pharynx
dysphagia
Stridor
Hoarse voice
Patient assessment: breathing anaphylaxis
Dyspnoea
Bronchospasm
Cyanosis
Tachypnoea
Hypoxia
Patient assessment: circulation anaphylaxis
Hypotension
tachycardia
dizziness
myocardial ischaemia
bradycardia in late stages
Patient assessment: disability anaphylaxis
confusion
urticaria
angioedema
abdominal pain
diarrhoea and vomiting
Urticaria
Hives/nettle rash
Red on lighter skin, just raised on darker skin
Skin symptoms without ABC concerns = not anaphylaxis
Erythema
discolouration to the skin
normally redness/ligher/darker than normal
caused by blood flow to the superficial capillaries and leaking into tissues due to histamine increasing permeability
Angioedema
Swelling due to fluid in lower layers of skin.
Criteria for diagnosis of anaphylaxis
Sudden onset of symptoms
Life threatening airway/breathing/circulation problems
Skin and or mucosal changes ( 20% patients don’t have this ! )
Diagnosis criteria for allergic reaction
Onset over minutes to hours
skin and mucosal changes in absence of life threatening airway/breathing/circulatory changes.
Mortality points
Mortality = less than 1%
50% of mortalities due to circulatory collapse
50% due to respiratory failure
timings for serious effects
food 30-35 minutes
insect stings 10-15 minutes
IV medication within 5 minutes
EpiPen
Autoinjector containin 1:1000 up to 1mg adrenaline, same medication carried by ambulance
biphasic reaction
3% of cases, recurrence of symptoms after full resolution hours after the initial event. Transfer even without adrenaline administration for observation in case of biphasic reaction
Adrenaline
acts on alpha and beta- adrenergic receptors.
Acting on alpha receptors - vasoconstriction, increased PVR, increased BP, decreased oedema, lowers intraocular pressure.
Acting on beta receptors - bronchodilation, vasodilation, inhibition of mediator release, lowers peripheral BP
