Anaphylaxis Flashcards
What is anaphylaxis?
Severe life-threatening type 1 hypersensitivity reaction
Caused by exposure to allergen which patient has already been sensitised to meaning they already have IgE
Antigen binds with specific IgE
IgE stimulate mast cell degranulation via cross linking with receptor on mast cell
What is mast cell degranulation?
Release of histamine, PDG2, leukotrienes, PAF, tryptase
What is a type 1 hypersensitivity?
IgE mediated Occurs within minutes of exposure Resolves w/i hours Life threatening Managed with STRICT avoidance, antihistamine and adrenalin
How can you differentiated anaphylaxis from a non-anaphylaxis reaction?
Anaphylaxis involves a compromise of airway, breathing or circulation
What condition can present very similarly to an anaphylaxis reaction? How is it different?
What are the exacerbating factors associated with this condition?
Chronic spontaneous uritcaria
- causes hives and angioedema with break through itching and rash
- has slower onset then allergy and slower to resolve (w/i a few months)
- wake up with it rather than following exposure to anything i.e. NOT a response to allergen
Exacerbation factors:
- thyroid function
- physical stress i.e. anaemia/infection/liver problems
- emotional stress
- aparin or opiates
- Urticarial vasculitis (AI)
How might someone suffering from anaphylaxis present?
(Following hx of exposure to allergen w/i 60 mins of symptoms) SKIN -urticaria (hives) -itching -angio-oedema
AIRWAY:
- hoarse voice/stridor i.e. swelling of laryngeal cords
- change in tambre of voice i.e. due to swelling of vocal cords
- swelling of tongue + throat
BREATHING
- increased RR
- Wheeze
- cyanosis (late sign-> very bad)
CIRCULATION
- hypotension-> vasodilation + increased permeability
- tachycardia-> compensation for decreased BP
- MI
NEUROLOGICAL (due to decreased BF to brain)
- confusion + agitation
- LOC
- sense of impending doom (Neuro manifestation oh HypoTN)
Abdominal pain
What would be classed as an immediate reaction to allergen? How is it related to anaphylaxis?
Can be reaction to allergen which did not require adrenaline
Increases the risk of anaphylaxis occurring
What are common cause of anaphylaxis?
Drugs (Abx, anaesthetic, agents, RCM)
Foods (nuts, shellfish, fish, milk)
Insect stings
Latex
Idiopathic
What are the possible differential diagnoses for anaphylaxis?
Syncope/faint-> would be pale and Brady
Anxiety induced hyperventilation
Hypotension-> blood loss, sepsis
Scombroid poisoning-> histamine in tuna meat breaks down to histamine if not cooked or frozen enough
Mastocytosis-> increase number mast cells means increase number of products to induce anaphylaxis-like state
Carcinoid syndrome
Vocal cord dysfunction-> feeling of strangulation, normally associated with anaesthetics
Chronic urticaria + angioedema (most common diff)
C1-esterase inhibitor deficiency (only angioedema)
Direct mast cell activators (opioids)
What is the acute management of anaphylaxis?
A= secure airway B= o2 if needed +/- salbutamol to help wheeze C=IV bolus D=flat-> improves cerebral perfusion E=flushing,urticaria, angio-oedema
3 meds:
- IM adrenaline 0.5 mls (repeated after 5 mins if required)
- antihistamines= Chlorphenamine or certizine
- steroids= hydrocortisone
Why is IM route preferred to IV in anaphylaxis?
Anaphylaxis is associated with severe hypo-circulation meaning that IV route would not be as effective
What is the dose of adrenaline in auto-injectors? Why is it different to the dose given in hospital?
0.3 mls in auto-injector
Due to high doses of adrenaline being associated with arrhythmias
Therefor the lower dose is to ensure it is safe to be used in the community and acts as loading dose before patient can get in to hospital
What actions does adrenaline have which helps to counteract an anaphylaxis reaction?
Increased peripheral vasoconstriction
Increase peripheral vascular resistance
Increase BP and coronary artery perfusion
Decreased vascular permeability and angioedema
Induces bronchodilation via SM relaxation
Decreases inflammatory mediator release
What medication is used as part of supportive management of anaphylaxis? What is the function of supportive management?
Corticosteroids
- 200mg IV hydrocortisone
- 40mg oral
Antihistamine
-10mg chlorpheniramine IV
Function:
-preventi bi-phasic reaction i.e. can have second phase of symptoms 1-8 hrs after initial symptoms
What is measured to confirm an anaphylaxis reaction has occured?
When is it measure and why?
What would indicate an anaphylaxis?
Tryptase
- ASAP but w/i 6 hrs of reaction -> peak seen 2hrs after symptoms started i.e. has 1/2 life of 4-6 hrs
- measure again at baseline
- released from mast cells with inflammatory mediators but has longer 1/2 life
Anaphylaxis:
-increased compared to baseline
BUT= not everyone releases tryptase= so negative tryptase doesn’t mean anaphylaxis hasn’t occurred
