CBD 5: Anaphylaxis Flashcards
Sarah is a 16-year old girl who was eating at a restaurant with her family. After starting the main course, she noticed feeling hot and then some tingling in her lips. She began to feel anxious. Her parents noticed a rash on her face and neck.
a) Other relevant points in the history?
b) What is the name of the typical allergic rash?
a) History of allergies, contact with known allergen, history of asthma (increased mortality), previous anaphylaxis, EpiPen?
b) Urticaria - red, raised, itchy bumps (weals)
Anaphylaxis.
a) Define
b) 2 main criteria to diagnose
c) Initial features usually (80% cases)
d) Other possible features
e) vs. ‘anaphylactoid’ reactions
a) Severe, life-threatening, systemic IgE-mediated hypersensitivity reaction
b) - Sudden onset and rapid progression of symptoms
- Life-threatening airway and/or breathing and/or circulation problems.
c) Skin/soft tissue changes:
- angio-oedema (lips, eyelids, airway)
- urticaria
- flushing
d) - Gastrointestinal symptoms (e.g. vomiting, abdominal pain, incontinence)
- Psychiatric (anxiety and a “sense of impending doom”)
e) Anaphylactoid reactions are similar to anaphylaxis but are not IgE-mediated
Anaphylaxis: triggers
a) Food
b) Drug
c) Other most common
d) Other less common
a) Nuts (peanut, walnut, Brasil nut, almond, other), dairy, fish, strawberry, kiwi fruit
b) Antibiotics (penicillins, cephalosporins), anaesthetic drugs (NMBs, induction agents), NSAIDs, ACEIs, contrast media
c) Stings (wasp, bee, scorpion), venom
d) Latex, dyes
Anaphylaxis: fatalities
- Time course for
a) Food allergies/oral meds
b) insect stings
c) IV drugs
a) Food allergies/oral drugs (respiratory arrest after 30 mins)
b) Insect stings (shock after 15 mins)
c) IV drugs (shock within 5 mins)
Sudden onset of generalised urticaria, angioedema, and rhinitis - is this anaphylaxis? Why?
NO
Because the life-threatening features – an airway problem, respiratory difficulty (breathing problem) and hypotension (circulation problem) – are not present.
Anaphylaxis: AIRWAY problems
- Airway swelling (e.g. throat and tongue swelling)
- Hoarse voice
- Stridor
Anaphylaxis: BREATHING problems
- Shortness of breath – increased respiratory rate
- Wheeze (may have asthmatic features)
- Patient becoming tired
- Confusion caused by hypoxia
- Cyanosis (appears blue) – this is usually a late sign
- SpO2 < 92%
- Respiratory arrest
Anaphylaxis: CIRCULATION problems
- Signs of shock – pale, clammy
- Tachycardia
- Hypotension – feeling faint (dizziness), collapse
- Decreased GCS or LOC
- ECG changes
- Cardiac arrest
Anaphylactic shock: pathogenesis
Anaphylactic shock can be caused by:
- direct myocardial depression
- vasodilation > capillary leak > loss of circulating volume
Anaphylaxis: differentials
a) Life-threatening
b) Non life-threatening
a) - Life-threatening asthma – commonest in children
- Septic shock (children may have petechial rash)
- Other causes of shock/collapse/arrest
b) Non life-threatening conditions (these usually respond to simple measures):
• Faint (vasovagal episode) - bradycardia, responds to lying down and leg raising.
• Panic attack.
• Breath-holding episode in child.
• Idiopathic (non-allergic) urticaria or angioedema.
Anaphylaxis: management algorithm (Resus UK)
- definitive management
- adjuvant management (including A-E)
- monitoring
- how should mild-moderate allergic reactions be treated?
Doses:
- Adrenaline
x 20 = chlorphenamine dose
x 20 again = hydrocortisone dose
Assessment and diagnosis.
- ABCDE and assess for anaphylaxis
- Call for help
- Lie patient flat and raise legs
- ADRENALINE - 500 mcg IM (adults); repeat after 5 mins if no improvement
- Remove trigger if possible (eg. stop penicillin, remove bee sting)
Adjuvant management.
- Airway - establish - RSI if necessary
- Breathing - High-flow 100% oxygen: 15 L/min via NRB
- Circulation - gain IV access and give…
1. Chlorphenamine 10 mg IM/ slow IV injection (H1-blocker)
2. Hydrocortisone 200 mg IM/ slow IV injection (reduce risk of persistent/biphasic anaphylaxis)
3. IV fluid challenge: 500 - 1000 ml 0.9% NaCl
4. Asthma drugs if predominantly asthmatic features (follow asthma guidelines - salbutamol, ipratropium, magnesium, etc.)
Monitoring.
• Pulse oximetry
• ECG
• Blood pressure
- Take mast cell tryptase (immediately after emergency care, and then second sample 1 - 2 hours after)
- Continue to monitor patient for 6 - 12 hours*
*If < 16 years, should be admitted under paediatrics
Mild-moderate allergy.
- Give antihistamine - chlorphenamine (oral, IM or IV)
- Observe and be ready with adrenaline if needed
Adrenaline: doses
a) Adult IM (all above 12 years)
b) Paediatric IM (6 - 12, < 6 years)
c) In auto-injectors (epi-pens)
d) Intravenous (IV) dose
a) • Adult 500 mcg IM of 1 in 1,000 (0.5 mL)
b) • Child 6 -12 years: 300 mcg IM (0.3 mL)
• Child less than 6 years: 150 micrograms IM (0.15 mL)
c) Two available doses: 150 or 300 micrograms
d) - Adrenaline IV to be given only by experienced specialists.
Titrate: Adults 50 mcg (one-tenth of the IM dose); Children 1 mcg/kg
Adrenaline: mechanism of action
Alpha-receptor agonist.
- Reverses peripheral vasodilation, thereby increasing circulating volume and reducing oedema.
Beta-receptor agonist.
- Dilates the bronchial airways
- Increases the force of myocardial contraction
- Suppresses histamine and leukotriene release
- Inhibits mast cell activation
IM adrenaline.
a) Site of IM injection
b) Who should receive an auto-injector?
c) Prescription
d) How to use (note: may differ slightly between brands)
e) Advice after epi-pen use
a) Anterolateral aspect of the middle third of the thigh
b) - Where trigger is hard to avoid (eg. insect stings, foods)
- Where trigger is unknown (idiopathic anaphylaxis)
c) - 2 epi-pens
- Solution should be clear
d) - Symptoms of anaphylaxis or known trigger
- Remove safety cap from top of pen
- Withdraw arm to 10 cm from lateral thigh
- Stab/press (depending on brand) pen into thigh at 90 degree angle
- Hold in place for 10 seconds
- Remove pen and massage injection site for 10 seconds
- If after 5 minutes there are still symptoms, use second epi pen
e) - Always call 999 even if symptoms are improving
- Lie flat and raise legs (unless breathing difficulties - sit up and raise legs if possible)
- Check viewing window in pen - should go dark to signify that adrenaline has been injected
Post-resuscitation: plan
a) Investigation to confirm anaphylaxis
b) Further management
c) How long post-reaction should they be observed for?
d) What risks should be explained to patient?
e) Allergy testing
a) Serum mast cell tryptase (product of mast cell degranulation)
- First sample as soon as emergency treatment has been given and recovery begins
- Second sample 1 - 2 hours later (no later than 4 hours)
b) - Discharge on 3 days of prednisolone and antihistamine
- Referral to allergy specialist
- Patient education
- Give patient a red alert wristband
- Consider need for auto-injector based on risk of re-exposure
- Document allergy appropriately in notes and system
c) Minimum 6 hours (6 - 12 hours)
d) Biphasic reactions - return of anaphylactic features without repeat exposure (incidence: 1 - 20%) - risk is reduced by use of hydrocortisone
e) - 1st line - specific IgE to the allergen in question (eg. food, venom, drugs) - if positive, this is good indication of allergy (but false negative rate high)
- 2nd line - if IgE negative, proceed to skin prick testing*
- 3rd line - challenge (generally only done by specialist, eg. anaesthetist, and where urgent result needed) - use dilute/small concentration and observe for anaphylaxis
- False positive causes: any recent use of histamine-releasing drugs (eg. opiates, NSAIDs, NMBAs)
- False negative causes: any recent antihistamines, H2RAs, corticosteroids, certain anti-emetics and TCAs that affect histamine
