Allergies and anaphylaxis Flashcards
Allergy-
-abnormally powerful immune response to an antigen that usually pose no threat to the body
Triggers of allergic reactions
-food
-venom- bites, stings
-drugs- antibiotics, analgesics etc.
-other eg. latex, hair dye
Anaphylaxis-
-severe, life threatening, generalised or systemic hypersensitivity reaction
-further categorised by rapidly developing airway/ breathing/ circulation problems usually associated with skin and mucosal changes
What antibody causes the majority of symptoms of an allergic reaction
immunoglobulin e (IgE)
Steps in anaphylactic reaction
-antigen enters body
-triggers production of IgE antibodies
-IgE bind to surface of mast cell/ basophil
-subsequent exposure to same antigen
-antigen bridges gap between 2 antibodies
-causes degranulation of the mast cell/ basophil
-this releases histamine and other mediators
Effects of histamine
-blood clot
-secretion gastric acid
-vasodilation
-bronchoconstriction
-increase permeability of capillaries
-adrenaline released
-swelling/ inflammation
-tachycardia
Patient assessment for anaphylaxis
Airway
-angioedema- fluid build up in skin
-dysphagia- difficulty swallowing
-stridor
-hoarse voice
Breathing
-bronchospasm= wheeze
-tachypnoea/ dyspnoea
-cyanosis
-hypoxia
Circulation
-hypotension
-tachycardia
-dizzy
-myocardial ischaemia- decrease blood flow through arteries
-bradycardia (late sign)
Disability/ exposure
-confusion/ reduced GCS
-urticaria- hives
-angioedema- fluid build up in skin/ swelling
-erythema- patch of skin discolouration
-abdominal pain
-diarrhoea and vomiting
Erythema
what is it and what causes it
-discolouration of skin
-caused by increased blood flow to superficial capillaries
Angioedema
what is it and where can it be found
-layers of swelling in the skin
-can be in the mouth, face, upper airway etc
Criteria for anaphylaxis diagnosis
ALL OF FOLLOWING CRITERIA ARE MET
-sudden onset and rapid progression of symptoms
-life threatening airway/ breathing/ circulation problems
-skin/ mucosal changes (flushing, urticaria, angioedema)
Criteria for allergic reaction diagnosis
Mild- moderate
-onset has progressed over minutes to hours
-skin and or mucosal changes in the absence of life threatening features
-if suspected mild to moderate allergic reaction, give oral antihistamine
Mortality and outcomes after different stimuli
-mortality= less than 1%
-50% fatalities due to circulatory collapse/ shock
-other 50%= respiratory failure
Outcomes
-food- respiratory arrest after 30-45 mins
-stings- collapse with shock after 10-15 mins
-IV meds- death within 5 mins
Management/ treatment of anaphylaxis
-may be given epi pen before we get there that contains 1:1000 (contains o.3mg)
-if suspected anaphylaxis, all patients should go to hospital due to risk of biphasic reaction (symptoms reappear hours after event)
Management flowchart for anaphylaxis according to JRCALC
-assess ABCDE
-diagnosis- look for sudden onset airway/ breathing problems or unusual skin changes
-if possible remove trigger (bee sting etc), lie flat, possibly raise legs
-administer adrenaline- IM ONLY into thigh
-establish airway, give O2
-apply monitory- SPO2, ECG, BP
-if no response after 5 mins, give more IM adrenaline, consider IV fluid bolus if hypotensive
-if still no improvement follow refractory anaphylaxis algorithm
Refractory anaphylaxis algorithm (anaphylaxis that isn’t responding to 2 doses adrenaline)
-establish IV access
-give fluids if haven’t already
-give IM adrenaline every 5 mins
-give O2
-monitor HR, BP, SPO2, ECG
-transport rapidly with pre alert
