anaphylaxis

Question 1

anaphylactic shock vs anaphylactoid reaction

Answer 1

Type-I IgE-mediated hypersensitivity reaction. Release of histamine and other agents causes: capillary leak; wheeze; cyanosis; oedema (larynx, lids, tongue, lips); urticaria. More common in atopic individuals.

An anaphylactoid reaction results from direct release of mediators from infl ammatory cells, without involving antibodies,
usually in response to a drug, eg acetylcysteine

Question 2

Signs and symptoms of anaphylaxis

Answer 2

• Itching, sweating, diarrhoea and vomiting, erythema, urticaria, oedema
• Wheeze, laryngeal obstruction, cyanosis
• Tachycardia, hypotension

Question 3

Management of anaphylaxis 8

Answer 3

1 - Secure the airway—give 100% O2 Intubate if respiratory obstruction imminent

2 - Remove the cause; raising the feet
may help restore the circulation

3 - Give adrenaline IM 0.5mg (ie 0.5mL of 1:1000)
Repeat every 5min, if needed as guided by BP, pulse,
and respiratory function, until better

4 - Secure IV access

5 - Chlorphenamine 10mg IV(a first-generation alkylamine antihistamine used in the prevention of the symptoms of allergic conditions such as rhinitis and urticaria) and hydrocortisone 200mg IV

6 - IVI (0.9% saline, eg 500mL over ¼h; up to 2L may be needed)
Titrate against blood pressure

7 - If wheeze, treat for asthma (p820)
May require ventilatory support

8 - If still hypotensive, admission to ICU and an IVI of adrenaline
may be needed ± aminophylline (p821) and nebulized
salbutamol (p821): get expert help.

Question 4

medium term treatment of anaphylaxis (ie after the immediate stuff)

Answer 4

Further management

• Admit to ward. Monitor ECG.
• Measure mast cell tryptase 1–6h after suspected anaphylaxis.
• Continue chlorphenamine 4mg/6h PO if itching.
• Suggest a ‘MedicAlert’ bracelet naming the culprit allergen.
• Teach about self-injected adrenaline (eg 0.3mg, Epipen®) to
prevent a fatal attack.
• Skin-prick tests showing specifi c IgE help identify allergens
to avoid.