Anaphylaxis Flashcards
How do you characterise anaphylaxis?
The RCUK (resuscitation council uk 🇬🇧) characterise it as life threatening problems involving the:
- Airway oedema
- Breathing - Bronchospasm ( spasm/ contraction of the airway) - tachypnoea (rapid breathing)
- Circulation - Tachycardia
- skin and mucosal changes
What is biphasic anaphylaxis?
- After complete recovery from anaphylaxis a recurrence of symptoms within 72 hours with no further exposure to the antigen.
- It is managed in the same way as anaphylaxis
What is Idiopathic anaphylaxis?
Where no identifiable tumulus can be found all known causes of anaphylaxis must be excluded before this diagnosis can be made.
5 examples of relevance…. GO
- Literature generally suggests that anaphylaxis is increasing in the general population.
- An alteration in immunological status due to the increased progesterone level during pregnancy may predispose pregnant women to anaphylaxis
- Anaphylaxis is seen more in children with an estimated 1 in 170 children compare to 30 per 100000 adults
- Food is common trigger in children, where as medicinal products in adults are a more common trigger
- Approx 20 deaths a year from anaphylaxis in the UK 🇬🇧 from anaphylaxis
What are the potential causes of anaphylaxis?
In theory any food glycoproteins can cause an anaphylaxis.
- The majority of anaphylaxis reactions are caused by the immune system responding to the protein antigens.
- So anything that has a high level if protein can be a potential risk factor for life threatening anaphylactic reactions
Examples of food with high protein.
- Eggs
- Nuts
- Milk
- Fruit and veg
What is catamenial anaphylaxis?
This is a syndrome of hypersensitivity induced by endogenous progesterone secretion. Patients may experience a cyclic pattern of attacks during the pre- menstrual part of the cycle
- Occurs in women
What are the 5 Co- factors that amplify anaphylaxis?
1- Exercise 2- Acute infection ie cold or fever 3- Emotional stress 4- Disruption of routine ie travel 5- Pre menstrual status (female only)
Explain the time course for fatal anaphylaxis… GO
- When anaphylaxis is fatal death usually occurs very soon after the contact with the trigger.
Fatal food reactions- causes respiratory arrest after 30-35 mins
Insect stings - 10-15 mins
Intravenous medication after 5 mins.
When does anaphylaxis occur?
It occurs when a foreign antigen (primarily proteins) causes an immunological response from an individual leading to the release of histamines and other substances causing systematic symptoms
Who is at risk of anaphylaxis?
- Anaphylaxis is driven by immunoglobulin E (IgE)
- some people are referred to as being ATOPIC
- This means they have an increased level of IgE in their immune system.
- The increase in IgE manifests via conditions such as eczema, hay fever, asthma and anaphylaxis
What is the pathophysiology pathway for anaphylaxis?
- Antigen enters the body
- Antigen attaches its self to mast and basophil cells (both white cells)
- The body now produces IgE antibodies
- Antibodies are used by the immune system to identify and destroy antigens
- The body now has a primary response
- A memory is laid down
- The person is now referred to as being sensitised
- These changes take place at a cellular level
- On the second contact to the antigen after someone has become sensitised.
- Mast and basophil cells will degranulate / rupture
What are the substances released by the mast and basophil cells when they rupture?
- Heparin (anticoagulant)
- Histamine ( vasodilator + increases tissue permeability)
- Serotonin ( bronchoconstrictor)
- Platelet activating factor (clotting)
Histamine acts on the H1 and H2 receptors (found in blood vessels)
What are the adverse effects of histamine?
- Hypotension
- Tachycardia
- Bronchospasm
- Angioedema ( deep muscle swelling)
- Increased acidity
- Flushing
- Itching
- Hypotension (low BP)
- Plasma extravasation into the tissues causing hypovolaemic shock(loss of water )
How does hypovolaemic shock develop in anaphylaxis?
- Activation of the H1 and H2 receptors caused by histamine
- Allows waste to move out of the capillary and into the tissues.
- This results in fluid loss And ultimately hypovolaemic shock.
Why does your heart rate increase when your BP falls
- Drop in BP
- Baroreceptors in cardiovascular 🫀 system pick up three change in BP
- The baroreceptors send impulses to the medulla oblongata
- The medulla oblongata send impulses to the Vegas nerve (release the brake)
- The heart rate subsequently increases
Why does your BP fall in anaphylactic shock?
- Your Bp falls because of vasodilation and increased tissue permeability because of the release of histamine.
- So the trigger for causing low BP is histamine
MEGA PRINCIPLE 5
What can happen when your BP falls in relation to O2?
- When your BP falls the potential level of O2 to the brain can fall because the amount of blood 🩸 travelling to the brain 🧠 has decreased.
- this can cause confusion, loss of consciousness, starvation of O2 from the brain
MEGA PRINCIPLE 6
What can happen when your BP falls in relation to the kidneys?
- When BP falls the perfusion of blood 🩸 to your kidneys can fall.
- Our kidneys then consider you as dehydrated and will initiate a hormone release such as antidiuretic hormone or aldosterone.
- Meaning the urine output will be reduced.
What does serotonin do during anaphylaxis?
It causes either vasoconstriction (especially in renal vessels) or vasodilation.
- Causes venous constriction
- Promotes platelet activation
- Increases capillary permeability
- Causes bronchoconstriction
- It is also an important molecule involved in pain transmission
MEGA PRINCIPLE 7
What happens when your BP falls in relation to respiratory system?
- When BP falls the resp system bronchoconstricts
- This means O2 uptake may fall and that may mean because Hoyt not delivering or taking in as much O2
- You have to switch form aerobic to anaerobic respiration.
- A consequence of this is the production of lactate acid and your Ph will fall.
- When your Ph falls the resp rate increases.
- The chemoreceptor send impulses medulla oblongata
- The medulla oblongata sends impulses to the phrenic nerve
- The phrenic nerve controls the lungs 🫁 and makes the resp rate increase in an effort to get rid of the excess CO2 which acts like an acid
What does Platelet activating factor (PAF) do?
- PAF is a potent activator and mediator of many leukocytes functions including:
- Platelet aggregation
- Degranulation/ rupture
- Inflammation
- Anaphylaxis
What is tryptase and how can a mast cell tryptase test help diagnose anaphylaxis?
- Tryptase is an enzymes released by mast and basophil cells during an anaphylactic reaction.
- Mature tryptase shows mast cell degranulation and is elevated in a systematic reaction.
- Currently we only test for total tryptase
- Tryptase is realised in 30- 60 mins following activation and its half life is - 2 hours allowing a longer test window
- levels above 10-11.4 ng/ml are consistent with anaphylaxis
How do you conduct a mast cell tryptase test?
- After a suspected anaphylactic reaction in people over 16. Take timed blood samples for the mast tryptase testing as follows:
- 1st sample as as possible after the emergency treatment has started
- 2nd sample ideally within 1-2 hours (but no later the 4 from the onset of symptoms (NICE 2011)
Where are mast and basophil cells found?
- The respiratory 🫁 system
- Cardiovascular 🫀 system
- Gastrointestinal system
- Skin
What are the 5 products of mast cell activation?
1- Histamine 2- Proteoglycans 3- Cytokines ( IL-4, IL-5, IL-6, IL-8, IL-13, TNF, Fibroblasts, Growth factor stem cell factor 4- Lipid mediators 5- Protease
What are the 6 products of basophil activation?
1- Protease 2- Proteoglycans 3- Cytokines (IL-4, IL-8, IL-13, IgE etc) 4- Lipid mediator 5- Basic protein 6- Histamine
What does adrenaline do?
- Releases smooth muscle contraction,
- Increases heart muscle contraction
- Causes vasoconstriction systematically (improving BP)
- Causes bronchiole dilation ( making breathing easier)
why can pregnant women not have adrenaline?
- It can cause uterine vasoconstriction which results in hypoxic damage to the fetus
- However mums survival takes priority.
How do we give adrenaline?
Adrenaline is given intramuscularly every five mins if no improvement is seen.
