Allergy

Question 1

What is the role of H2 blockers in Allergy?

Answer 1

H2 blockers such as Ranitidine can help prevent further histamine release and augment H1 blockers, they also have some evidence for preventing delayed/late phase reactions

Question 2

What are the 2 types of anaphylaxis?

Answer 2

Immunological
- IgE mediated type 1 hypersensitivity reaction

Non-immunological
- Activation of Mast Cells and Basophils by an alternate route
- Vancomycin red man syndrome
- Propofol/Paclitaxel direct complement activation
- Opioid direct histamine release
- Cryoglobulinaemia and cold urticaria
- Some MAB’s and chemotherapy
- NSAID anaphylaxis

Question 3

What are the most common causes of fatal anaphylaxis? What are the risk factors?

Answer 3

Causes
- Food (peanuts)
- medications (beta lactams 1)
- insect stings (hymenoptera)

Risks
- No previous history of anaphylaxis (for drug and insects)
- Previous mild anaphylaxis (for food, underestimate the risk)
- Rapidly progressive anaphylaxis
- Large exposure to precipitant
- Concomitant Asthma
- Delayed adrenaline administration
- Upright posture (PEA from vasoplegic shock)
- Concomitant Cardiopulmonary disease

Epinephrine not working
- Medication interactions ie beta blockers, ACE inhibitors
- Epipen expired
- Not IM injection (ie sub cut)
- Inappropriate dose (paeds)
- Given too late
- Rapid progression

Question 4

What are the indications for discharge from ED post Anaphylaxis?

Answer 4

• Obs all stable
• No ABC compromise
• Allergen now gone (including ingested food allergen)
• > 4hrs since initial reacion and last dose of adrenaline
• Symptoms absent/improving (ie rash) without therapy in last 2hrs
• Adequate social situation
• Has epipen/script and advice

Question 5

What are the indications for an allergy specialist referral for anaphylaxis?

Answer 5

• 1st time anaphylaxis and has been given Epipen
• Severe reaction without obvious trigger
• Suspected food, drug or exercise induced anaphylaxis
• Anaphylaxis amenable to immunotherapy (ie hymenoptera)

Question 6

What is the definition of anaphylaxis?

Answer 6

Question 7

What alternative vasoactive drugs can be used for anaphylaxis?

Answer 7

Question 8

What drugs might be used to treat known C1 esterase inhibitor deficiency angioedema or as a hail mary for refractory angioedema?

Answer 8

Question 9

When do biphasic reactions occur and who is at risk?

Answer 9

Question 10

When starting a dirty adrenaline infusion of 1mg in 1000mls, what is the typical starting dose?

Answer 10

0.1mcg/kg/min

5mls/kg/hr

Generally easier to titrate to mls/hr with this concentration