Anaphylaxis

Question 1

Define anaphylaxis.

Answer 1

Acute, systemic + life-threatening allergic response to a trigger caused by release of immune + inflammatory mediators from basophils + mast cells.

>, 2 organ systems are involved, e.g. skin, upper + lower airways, cardiovascular, neurological, + GI systems, in this order of priority or in combination.

Question 2

Explain the aetiology/risk factors of anaphylaxis.

Answer 2

Exposure to allergen in pre-sensitised individuals causes immune-mediated anaphylaxis.

Common allergens: drugs, foods + insect stings, but exercise +/- presence of an allergen may also be a trigger.

Sometimes, a cofactor (e.g. NSAID, alcohol, or another food) is required to provoke food-associated + exercise-induced anaphylaxis.

Most common trigger (up to ⅓ of cases) is food.

Question 3

Summarise the epidemiology of anaphylaxis.

Answer 3

Anaphylaxis is under-reported + is difficult to estimate as study definitions + criteria vary
Incidence of food allergic reactions coded as anaphylaxis is highest in young children.
In kids, food allergy is most prevalent in the industrialised world + emerging economies of SE Asia, possibly due to an increased exposure to processed food.

Question 4

Recognise ABC problems of anaphylaxis.

Answer 4

A: Swelling of throat +/- tongue (hoarse voice + stridor)
B: dyspnoae + wheeze
C: Hypotension, Tachycardia

Question 5

Give 4 skin/ mucosal membrane manifestations of anaphylaxis

Answer 5

Erythema
Urticaria, pruritus
Angioedema
Sneezing

Question 6

Give 4 respiratory manifestations of anaphylaxis

Answer 6

SOB, tachypnoea
Wheezing, stridor
Cough
Hypoxia, cyanosis

Question 7

Give 3 GI manifestations of anaphylaxis

Answer 7

N+V
Abdo pain
Diarrhoea

Question 8

Give 3 cardiac manifestations of anaphylaxis

Answer 8

Hypotension
Tachycardia, weak p pulses
Signs of end-organ dysfunction: skin mottling, altered mental status, anuria, mottling

Question 9

Identify appropriate investigations for anaphylaxis and interpret the results.

Answer 9

During: Ix take too long.
Serum tryptase level: high, peaks at 1-2h

Question 10

What is the normal course of an anaphylactic reaction? What is a biphasic reaction?

Answer 10

Most commonly peak in 30 mins
Sx can resolve, then come back hours later without further exposure to trigger

Question 11

Describe the acute management of anaphylaxis

Answer 11

A-E resus
Remove trigger
Position comfortably
IM Adrenaline anterolateral thigh
High flow O2, pulse ox, ECG + BP
Asses after 5 mins, repeat adrenaline + IV fluids 10ml/kg

Question 12

How does adrenaline improve symptoms of anaphylaxis?

Answer 12

Causes vasoconstriction: decreases swelling + increases BP
Increases HR + contractility- prevents cardiovascular collapse
Relaxes smooth muscles of bronchi

Question 13

What dose of adrenaline is given per age group?

Answer 13

> 12y: 0.5 mg IM (0.5ml 1:1000 solution)

6-12y: 0.3 mg IM (0.3ml 1:1000 solution)

6m-6y: 0.15 mg IM (0.15ml 1:1000 solution)

< 6 months: 0.01mg/kg IM (0.01ml/kg 1:1000 solution)

Question 14

Summarise the prognosis for patients with anaphylaxis.

Answer 14

Individuals with previous reactions are at higher risk for recurrence.
Severity of previous reaction does not necessarily predict severity of a subsequent reaction.

Question 15

What should patients be provided with on discharge?

Answer 15

Observe for >,6h
Refer to allergy clinic
Educate on signs + Sx of anaphylaxis + how to use epipens
Prescribe 2 epipens