Anaphylaxis

Question 1

Pathophysiology of anaphylactic shock.

Answer 1

A type I IgE mediated HS reaction.

There is release of histamine and other agents.

This casues leaky capillaries.

It is more common in atopic individuals.

Question 2

Clinical features of anaphylactic shock.

Answer 2

Wheeze

Cyanosis

Oedema of larynx, lids, tongue and lips.

Urticaria

Itching, sweating, diarrhoea, vomiting, erythema.

Tachycardia

Hypotension

Question 3

Examples of precipitants.

Answer 3

Drugs like penicillin and contrast media in radiology.

Latex

Sings

Eggs, fish, peanuts, strawberries

Semen (rare)

Question 4

Mimics of anaphylaxis.

Answer 4

Carcinoid

Phaeochromocytoma

Systemic mastocytosis

Hereditary angioedema

Question 5

Management algorithm of anaphylaxis.

Answer 5

1 - Secure airway and give 100% O2, intubate if there is resp obstruction.

2 - Remove the cause and raise feet to help restore circulation.

3 - Give adrenaline IM 0.5mg (i.e. 0.5ml of 1:1000)
Repeat this every 5 min if needed as guided by BP, pulse and resp function until better.

4 - Secure IV access

5 - Chlorphenamine 10mg IV and hydrocortisone 200mg IV

6 - IVI (0.9% saline e.g. 500 ml over 15 min up to 2L may be needed) Titrate this against BP.

7 - If wheeze treat for asthma and may req ventilatory support.

8 - If still hypotensive admit to ICE and an IVI adrenaline may be needed +/- aminophylline and nebulised salbutamol. Get expert help.

Question 6

Further management of anaphylactic shock.

Answer 6

Admit to ward and monitor ECG

Measure serum 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 to prevent a fatal attack.

Skin-prick tests showing specific IgE help identify allergens to avoid.

Question 7

What is the dose of adrenaline if given IV?

Answer 7

100 micrograms/min titrating with response.

This is 0.5 ml of 1:10000 solution IV per minute, compared to 1000 in IM.