Anaphylaxis Flashcards
What is the primary cause of hypotension during general anaesthesia?
Sympathetic suppression causes vasodilation leading to hypotension
This is anticipated and is typically supported with medications such as metaraminol/noradrenaline/phenylephrine (if tachycardic), or ephedrine (if bradycardic)
List the types of shock associated with hypotension.
- Hypovolaemic shock: eg. massive blood loss
- Obstructive shock: eg. PE, tamponade, tension pneumothorax
- Cardiogenic shock: cardiomyopathy, myocardial depression
- Distributive shock: sepsis, Anaphylaxis
What are common causes of urticaria?
- IgE mediated allergic reactions: beta-lactams, latex
- Non-IgE mediated: mast cell degranulation
- NSAIDs: either allergic or non-allergic through COX1 inhibition
- Transfusion reactions
- Radiocontrast medium
- Infection
- Systemic disease
Define angioedema.
Localised swelling of skin or mucosal tissues due to loss of vascular integrity and extravasation of fluid into the interstitium
It may occur in isolation, with urticaria, or as part of anaphylaxis.
What are the five types of angioedema?
- Acute allergic angioedema: food, drugs, venom, latex
- Non allergic drug reactions: ACE inhibitors
- Idiopathic angioedema
- Hereditary angioedema: rare autosomal dominant disorder
- Acquired C1 inhibitor deficiency
What criteria indicate a high likelihood of anaphylaxis?
highly likley if any one of the following three criteria are fulfilled:
* Acute onset of illness with skin or mucosal involvement and respiratory compromise or reduced BP/symptoms of end organ dysfunction
* Acute onset of 2 or more symptoms after exposure to a likely allergen
* Reduced BP after exposure to known allergen
What is the pathophysiology of anaphylaxis?
Acute multisystem syndrome from sudden release of mast cell and basophil derived mediators into circulation
may be:
o IgE mediated – meaning allergen binds to IgE
o Non-IgE mediated
o Idiopathic
Mediators include histamine, tryptase, and prostaglandins.
What are the multisystem effects of anaphylaxis?
- Cardiac: depressed myocardial function, vasodilation, fluid leak from capillaries
- Airway obstruction: tissue swelling, bronchospasm, altered smooth muscle tone
What immediate actions should be taken when anaphylaxis is suspected?
- Remove triggers
- Stop procedures
- Call for help
- Assign team roles
- Consider early intubation
- Confirm FiO2
- Leg elevation
- Large bore IV access x2
- Fluid resuscitation 20ml/kg
What airway management steps should be taken for a patient not maintaining their own airway?
- Jaw thrust
- Airway adjuncts
- Bag-valve mask with high-flow oxygen
- Rapid assessment for stridor or respiratory arrest
you should always anticipate a difficult airway in anaphylactic patients. what steps should you take to mitigate this
o Always call for help from the most experienced person
o Consider use of video laryngoscope for the first attempt
o If glottic aperture is not accessible due to oedema, emergency cricothyrotomy or tracheostomy may be needed (refer to difficult airway protocols)
o Do not make prolonged intubation efforts – patient is not getting any oxygen
What are risk factors for refractory anaphylaxis management?
- Patients taking beta blockers
- Patients on ACE inhibitors
- Spinal blockade
what are the trouble shooting methods for refractory anaphylaxis
What should be done after the acute management of an anaphylaxis episode?
- MDT discussion on surgery continuation
- Observation for >6 hours in ICU/HDU
- Administer oral antihistamines and steroids
- Investigate with serum tryptase if diagnosis is unclear
*referral to immunologist if reaction severe or cause unknown
what investigation is used to confirm anaphylaxis
serum tryptase
what is the role of oral antihistamines and steroids in anaphylaxis
Use oral antihistamines to Sx such as pruritic, urticaria, angioedema
Steroids: dexamethasone may decrease recurrence of symptoms
