Allergic Disorders

Question 1

Define anaphylaxis

Answer 1

Severe, life-threatening, generalised or systemic hypersensitivity reaction characterised by rapidly developing airway and/or breathing and/or circulation problems usually associated with skin and mucosal changes

Question 2

Common triggers of anaphylaxis

Answer 2

Food, drugs and venom. Nuts are the most common food, anaesthetics, NSAIDS, antibiotics and aspirin are the most common drugs

Question 3

Length of time for different triggers to cause respiratory arrest

Answer 3

Food- 30 minutes
Insect stings- 15 minutes
IV medications- 5 minutes

Question 4

Risk of recurrence of anaphylaxis

Answer 4

1 in 12 per year

Question 5

What 3 criteria are required in order to diagnose anaphylaxis?

Answer 5

1- Sudden onset and rapid progression of symptoms
2- Life-threatening airway +/- breathing +/- circulatory problems
3- Skin and mucosal changes (can be subtle or absent in 20% of cases)

Question 6

Differential diagnosis of anaphylaxis

Answer 6

Angio-oedema, asthma, anxiety attack, breath-holding episode in a child, foreign body aspiration, hypoglycaemia, PE, urticaria, vasovagal episode, mastocytosis, carcinoid syndrome, scombroid food poisoning, seizure disorder, septic shock

Question 7

Management of anaphylaxis

Answer 7

• DRSABC
• If unresponsive and not breathing start CPR
• Give IM Adrenaline 1:1000 as per age-related guidelines. Repeat after 5 minutes if no improvement. Give every 5 minutes until ambulance arrives if not improving
• Remove the trigger if possible
• If possible give oxygen, attach monitoring, fluid bolus if shocked or poor response to adrenaline, nebs if wheezy

Question 8

What position should you manage a person with anaphylaxis in?

Answer 8

• They must not stand or walk
• May prefer semi-recumbant position if airway or breathing problems
• Lying flat with elevated legs can help low BP
• Left side if pregnant

Question 9

Emergency drug doses for anaphylaxis (Adult or child over 12 years)

Answer 9

Adrenaline 1:1000 IM- 500 micrograms (0.5mL)
Chlorphenamine (Slow IV or IM)- 10mg
Hydrocortisone (Slow IV or IM)- 200mg
Salbutamol (neb)- 5mg

Question 10

Emergency drug doses for anaphylaxis (Child aged 6-12 years)

Answer 10

Adrenaline (IM) 1:1000- 300 micrograms (0.3mL)
Chlorphenamine (Slow IV or IM)- 5mg
Hydrocortisone (Slow IV or IM)- 100mg
Salbutamol (neb)- 5mg

Question 11

Emergency drug doses for anaphylaxis (Child aged 6 months- 6 years)

Answer 11

Adrenaline (IM) 1:1000- 150 micrograms (0.15mL)
Chlorphenamine (Slow IV or IM)- 2.5mg
Hydrocortisone (Slow IV or IM)- 50mg
Salbutamol (neb)- 2.5mg

Question 12

Define angio-oedema

Answer 12

Swelling of deep-dermis, subcutaneous or submucosal tissue. Often affecting the face (tongue, lips and eyelids), genitalia, hands or feet. Less commonly swelling of the bowel or airway. Most commonly occurs with urticaria (superficial swelling of the epidermis and mucous membranes resulting in a red, raised, itchy rash or weals) but may occur in isolation

Question 13

What is the difference between anaphylaxis and angio-oedema?

Answer 13

The mechanisms are the same as both histamine and/or bradykinin are involved. In anaphylaxis the reaction is more marked, resulting in an increase in vascular permeability and subsequent circulatory collapse

Question 14

Causes/ types of angio-oedema

Answer 14

• Acute allergic angio-oedema
• Non-allergic drug reactions
• Hereditary angio-oedema
• Acquired angio-oedema
• Idiopathic angio-oedema

Question 15

Define acute allergic angio-oedema

Answer 15

Usually mast-cell mediated (typically IgE) and histamine induced. Almost always occurs with urticaria within 1-2 hours of exposure to the allergen which could be food, drugs, insect venom, latex or contrast media. Usually self-limiting and resolves in 1-3 days. Relapses are common and unpredictable.

Question 16

Define non-allergic drug reactions

Answer 16

Occur days to months after taking the eliciting drug, most commonly ACE inhibitors. Can get more severe if the drug is not discontinued and in 20% of cases can be life-threatening.

Question 17

Define hereditary angio-oedema

Answer 17

C1 esterase inhibitor (C1-INH) deficiency. Rare and potentially life threatening genetic abnormality. Leads to bradykinin overproduction and subsequent abrupt increase in vascular permeability. Most attacks are spontaneous but can be triggered by mild trauma, viral illness, stress, cold exposure, pregnancy or certain foods/drugs. Usually presents after puberty. and required life-long treatment.

Question 18

Define acquired angio-oedema

Answer 18

Acquired C1 esterase inhibitor (C1-INH) deficiency. Usually secondary to lymphoma or connective tissue disorder eg SLE. Rarer than HAE. Usually presents after the 4th decade of life. Similar triggers to HAE.

Question 19

Define idiopathic angio-oedema

Answer 19

Usually a chronic and relapsing angio-oedema with an unknown cause. Many cases thought to be auto-immune in cause. Chronic and relapsing course.

Question 20

Differential diagnosis of angio-oedema

Answer 20

Acute contact dermatitis, cellulitis, connective tissue disorders, erysipelas, idiopathic scrotal oedema in children, lymphoedema, Rosenthal-Melkersson syndrome (recurrent facial oedema, peripheral facial nerve palsy and tongue fissuring), surgical abdomen

Question 21

What is the management of rapidly developing angio-oedema without anaphylaxis?

Answer 21

• Slow IV or IM chlorphenamine and hydrocortisone
• ED admission
• Arrange a review after discharge

Question 22

What is the management of stable angio-oedema without anaphylaxis?

Answer 22

• Try to identify cause, stop ACE

- If symptoms need treated offer non-sedating anti-histamine +/- short course of oral corticosteroid.

Question 23

When would you refer to an allergy clinic?

Answer 23

• Suspect HAE or AAE
• Symptoms persist or recur 3 months after stopping ACE
• Cause not identifiable or avoidable