Anaphylaxis Flashcards
Define Anaphylaxis
Acute, severe, generalised or systemic, hypersensitivity reaction that is characterised by rapidly developing life-threatening airway and/or breathing and/or circulation problems
Aetiology of Anaphylaxis
Exposure to an allergen in pre-sensitised individuals. Common allergens:
- Foods (1-3/-1/2) e.g. peanuts
- Drugs e.g. penicillin, NSAIDs, anaesthesia, opioids
- Insect stings e.g. wasps and bees
- Latex
- Contrast agents
Can require a co-factor e.g. NSAIDs, alcohol, another food, exercise to provoke anaphylaxis
Pathophysiology of Anaphylaxis
Immune-mediated: IgE- mediated or immune complex/complement mediated by massive degranulation or release of pro-inflammatory mediators and cytokines from basophils and mast cells
Non-immunologic: mast cell or basophil degranulation without Ab involvement e.g. reaction to vancomycin, codeine, ACEi
Inflammatory mediator release e.g. histamine, tryptase, chymase, histamine-releasing factor, PAF, prostaglandins and leukeotrienes → bronchospasm, increased capillary permeability and reduced vascular tone → tissue oedema
Symptoms of Anaphylaxis
Acute onset of symptoms on exposure to allergen (minutes to an hour)
SOB, sensation of choking Wheezing Hoarse voice Swelling of lips and face Pale, clammy skin Urticaria, erythema, pruritus Confusion or disorientation Nausea, vomiting, diarrhoea, incontinence Abdominal cramps and pain Agitation, anxiety, sense of doom
± biphasic reaction - two phases (symptoms return without re-exposure to the allergen)
Signs of Anaphylaxis on examination
Tachycardia, hypotension
Wheeze, inspiratory stridor, hoarse voice, accessory muscle use with hyperinflation
Cyanosis, pallor, clammy skin
Swelling of lips and face
Rhinitis, bilateral conjunctivitis
Urticaria, erythema
Respiratory or cardiac arrest -> unconsciousness
Investigations for Anaphylaxis
CLINICAL DIAGNOSIS → treat immediately
ECG: non-specific ST changes
Allergen skin test (AFTER resus)
Mast cell tryptase: may be elevated
U+Es: normal
ABG: elevated lactate
IgE immunoassay (AFTER resus) e.g. Radioallergosorbent tests (RASTs)
CXR: hyperinflation interstitial fluid (AFTER resus)
Management for Anaphylaxis
Cardioresp. arrest => CPR
Otherwise:
- ABCDE
- Position the patient comfortably and remove any triggers
- Adrenaline IM into the anterolateral aspect of the middle 1/3 of the thigh (500mg IM)
- Repeat adrenaline at 5 min intervals according to response
- Establish airway + high flow oxygen
- IV fluids (500-1000mL)
- Serial assessment with pulse oximeter, ECG and BP monitor
Consider: Nebulised adrenaline for marked stridor Nebulised SABA for bronchoconstriction 5mg in adults IV atropine if bradycardia IV glucagon if no response to adrenaline
What position should a patient be put in if they are experiencing anaphylaxis for the following: Feels faint Predominant airway/breathing problems Circulation problem Unconscious Pregnant
Feels faint: Do NOT sit or stand them up
Predominant airway/breathing problems: sit them up
Circulation problems: lie flat ± legs up
Unconscious: recovery position
Pregnant: on their left
What is the dose of adrenaline given for patients in anaphylaxis in adults, children 6-12 and children <6
Children <6: 0.15mg
Children 6-12: 0.3mg IM
Adults: 0.5mg IMc
What is the management after the initial anaphylaxis
Preventing a biphasic reaction:
- Antihistamine e.g.
- Corticosteroid
- Monitor for biphasic reaction
What are the doses for antihistamines e.g. chlorphenamine and corticosteroids in anaphylaxis after care
Chlorphenamine
Children <6: 2.5mh IM/IV
Children 6-12: 5mg IM/IV
Adults: 10mg IV/IM
Corticosteroid
Children <6: 50mg IV/IM
Children 6-12: 100mg IM/IV
Adults: 200mg IV/IM
Complications for anaphylaxis
Myocardial Infarction
Recurrence
Cardiorespiratory arrest
Prognosis for anaphylaxis
Severity of previous reactions does NOT predict the severity of future reactions
Individuals with previous reactions are at higher risk for recurrence
Prognosis depends mainly on co-morbs and patient age
