Anaphylaxis

Question 1

What is anaphylaxis?

Answer 1

a severe, life-threatening, generalised or systemic hypersensitivity reaction.

Question 2

What is the pathophysiology of anaphylaxis?

Answer 2

• Caused by a severe type 1 hypersensitivity reaction.
• Immunoglobulin E (IgE) stimulates mast cells to rapidly release histamine and other pro-inflammatory chemicals AKA mast cell degranulation.
• This causes a rapid onset of symptoms, with airway, breathing and/or circulation compromise.

Question 3

What are the two phases in the pathophysiology of anaphylaxis?

Answer 3

Sensitisation and Effector phase

Question 4

What is the sensitisation phase of anaphylaxis?

Answer 4

During the initial exposure to an allergen, antigen-presenting cells (APCs) process and present the allergen to naïve T cells, which differentiate into allergen-specific T helper 2 (Th2) cells.

Th2 cells release cytokines, such as interleukin-4 (IL-4) and IL-13, promoting the production of allergen-specific IgE antibodies by B cells.

The IgE antibodies bind to high-affinity receptors (FcεRI) on the surface of mast cells and basophils, sensitizing these cells for future allergen exposure.

Question 5

What is the effector phase of anaphylaxis?

Answer 5

Upon subsequent exposure to the same allergen, the allergen cross-links the IgE molecules on the surface of mast cells and basophils, triggering the release of preformed and newly synthesized inflammatory mediators.

Question 6

What are preformed mediators in anaphylaxis?

Answer 6

Histamine, tryptase, and chymase are stored in granules within mast cells and basophils and are rapidly released upon activation.

These mediators cause vasodilation, increased vascular permeability, smooth muscle contraction, and mucus secretion, leading to the clinical manifestations of anaphylaxis.

Question 7

What are newly synthesised mediators in anaphylaxis?

Answer 7

Following activation, mast cells and basophils synthesize and release various cytokines, chemokines, and lipid mediators, such as prostaglandins and leukotrienes.

These mediators contribute to the late-phase response, amplifying and prolonging the inflammatory process.

Question 8

What is Non-IgE-mediated anaphylaxis?

Answer 8

Although less common, non-IgE-mediated mechanisms can also contribute to anaphylaxis.

These include complement activation, direct mast cell activation by agents such as radiocontrast media or opioids, and IgG- or IgA-mediated immune complex formation.

Question 9

What are common identified causes of anaphylaxis?

Answer 9

• Food (e.g. nuts, shellfish, fish, milk, eggs) - the most common cause in children
• Drugs - penicillin and other abx, NSAIDs, chemotherapy
• Venom (e.g. wasp, bees, fire ants)
• Latex - natural rubber latex
• Idiopathic

Question 10

What does the Resus council define anaphylaxis as?

Answer 10

Sudden onset and rapid progression of symptoms

Airway and/or Breathing and/or Circulation problems

Airway problems may include:
- swelling of the throat and tongue →hoarse voice and stridor

Breathing problems may include:
- respiratory wheeze
- dyspnoea

Circulation problems may include:
- hypotension
- tachycardia

Question 11

What does it mean if there are no ABC problems?

Answer 11

the patient is technically not having anaphylaxis

Question 12

What differentiates an anaphylactic reaction from a non-anaphylactic reaction?

Answer 12

compromise of the airway, breathing or circulation.

Question 13

What do around 80-90% of patients have?

Answer 13

• Skin and mucosal changes
• generalised pruritus
• widespread erythematous or urticarial rash

Question 14

How does a patient with an anaphylactic reaction present?

Answer 14

• Hx of exposure to an allergen (although it can be idiopathic).

Rapid onset of allergic symptoms:
- Urticaria
- Itching
- Angio-oedema, with swelling around lips and eyes
- Abdominal pain

Question 15

What additional symptoms may indicate anaphylaxis?

Answer 15

• SOB
• Wheeze
• Swelling of the larynx, causing stridor
• Tachycardia
• Lightheadedness
• Collapse

Question 16

How is anaphylaxis managed?

Answer 16

• Immediate medical attention and management
• Call for help early (esp experienced paediatrician if speeds patient)
• Initial assessment ABCDE

After anaphylaxis diagnosis is established, can give three medications
- IM Adrenaline - repeated after 5 mins if required (most important)
- Antihistamines eg. chlorphenamine, cetirizine
- Steroids eg. IV hydrocortisone

Question 17

What is involved in the ABCDE assessment?

Answer 17

A – Airway: Secure the airway

B – Breathing: Provide oxygen if required. Salbutamol can help with wheezing.

C – Circulation: Provide an IV bolus of fluids

D – Disability: Lie the patient flat to improve cerebral perfusion

E – Exposure: Look for flushing, urticaria and angio-oedema

Question 18

What are the recommended doses of adrenaline?

<6 months

6 months - 6 years

6-12 years

Adult and child >12 years

Answer 18

< 6 months: 100 - 150 micrograms (0.1 - 0.15 ml 1 in 1,000)

6 months - 6 years: 150 micrograms (0.15 ml 1 in 1,000)

6-12 years: 300 micrograms (0.3ml 1 in 1,000)

Adult and child >12 years: 500 micrograms (0.5ml 1 in 1,000)

Question 19

How often can adrenaline be repeated?

Answer 19

Can be repeated every 5 minutes if necessary.

Question 20

What is the best site for IM injection?

Answer 20

anterolateral aspect of the middle third of the thigh.

Question 21

What is refractory anaphylaxis?

Answer 21

• Defined as respiratory and/or cardiovascular problems persist despite 2 doses of IM adrenaline
• IV fluids should be given for shock
• Expert help should be sought for consideration of an IV adrenaline infusion

Question 22

Rhesus council anaphylaxis guidelines pt 1

Answer 22

Question 23

Resus council refractory anaphylaxis guidelines

Answer 23

Question 24

Following stabilisation, what can patient with persisting skin symptoms be given?

Answer 24

Persisting skin symptoms eg. urticaria and/or angioedema

Can be given non-sedating oral antihistamines, in preference to chlorphenamine,

Question 25

How should children be managed after the event?

Answer 25

1. All children should have a period of assessment and observation after an anaphylactic reaction, as biphasic reactions can occur, meaning they can have a second anaphylactic reaction after successful treatment of the first.
2. Children should be admitted to the paediatric unit for observation.
3. Mast Cell Tryptase levels
4. Education and follow-up of the family and child.
   - About allergy, avoiding allergens, identifying signs of anaphylaxis
   - Train parents for BLS
   - specialist referral for diagnosis, education, follow up, and adrenaline auto injector training

Question 26

What can be said about eliciting if a patient had a true episode of anaphylaxis? And what can be done in this case?

Answer 26

sometimes it can be difficult to establish whether a patient had a true episode of anaphylaxis.

Serum tryptase levels can be taken as they remain elevated for up to 12 hrs following acute episode of anaphylaxis

Question 27

What can be used to confirm anaphylaxis? Why is this used?

Answer 27

• Measuring the serum mast cell tryptase within 6 hours of the event.
• Tryptase is released during mast cell degranulation and stays in the blood for 6 hours before gradually disappearing.

Question 28

How should patients with a new diagnosis of anaphylaxis be managed?

Answer 28

1. Refer all pts with new diagnosis of anaphylaxis to specialist allergy clinic
2. Give adrenaline injector as interim measure before the specialist allergy assessment (unless reaction was drug-induced)
   - Give 2 adrenaline auto-injector
   - Provide training on how to use it

Question 29

What approach should be taken to discharge patients?

Answer 29

A risk-stratified approach to discharge should be taken as biphasic reactions can occur in up to 20% of patients

Question 30

What is recommended as a risk-stratified approach to discharge?

Answer 30

1. Fast-track discharge (after 2 hours of symptom resolution):
   - Good response to a single dose of adrenaline
   - Complete resolution of symptoms
   - Has been given an adrenaline auto-injector and trained how to use it
   - Adequate supervision following discharge
2. Minimum 6 hours after symptom resolution
   - 2 doses of IM adrenaline needed, or
   - Previous biphasic reaction
3. Minimum 12 hours after symptom resolution
   - Severe reaction requiring > 2 doses of IM adrenaline
   - Patient has severe asthma
   - Possibility of an ongoing reaction (e.g. slow-release medication)
   - Patient presents late at night
   - Patient in areas where access to emergency access care may be difficult
   - Observation for at least 12 hrs following symptom resolution

Question 31

What are trade names for adrenaline auto-injector devices?

Answer 31

Epipen
Jext
Emerade

Question 32

What patients are given adrenaline auto-injectors?

Answer 32

All patients with new diagnosis

All children and adolescents with anaphylactic reactions

May be considered in children with generalised allergic reactions (not anaphylaxis) with certain risk factors

Question 33

What risk factors (+generalised allergic reactions) may adrenaline auto-injectors be considered in? (paeds)

Answer 33

• Asthma requiring inhaled steroids
• Poor access to medical treatment (e.g. rural locations)
• Adolescents, who are at higher risk
• Nut or insect sting allergies are higher risk
• Significant co-morbidities eg. CVD

Question 34

Adrenaline auto-injector usage instructions?
(with specifics for epipen and jext)

Answer 34

1. Confirm diagnosis of anaphylaxis
2. Prepare device by removing the safety cap on the non-needle end. There is a blue cap on EpiPen and a yellow cap on Jext.
3. Grip the device in a fist with the needle end pointing downwards. The needle end is orange on EpiPen and black on Jext. Do not put your thumb over the end, because if the device is upside down you will inject your thumb with adrenalin and could risk losing it.
4. Administer the injection by firmly jabbing the device into the outer portion of the mid thigh until the device clicks. This can be done through clothing. EpiPen advise holding it in place for 3 seconds and Jext advise 10 seconds before removing the device.
5. Remove the device and gently massage the area for 10 seconds.
6. Phone an emergency ambulance. A second dose may be given (with a new pen) after 5 minutes if required.

Question 35

What are potential pregnancy-related symptoms of anaphylaxis?

Answer 35

Lower back pain
Fetal distress
Uterine cramps
Preterm labor
Vulvar or vaginal itching
May trigger maternal hypoxemia and hypotension which are potentially life‐threatening to both mother and fetus.

Question 36

How should these patients be managed in primary care?

Answer 36

After administration of epinephrine, patients with anaphylaxis should be placed supine with their lower limbs elevated. They should not be placed seated, standing, or in the upright position. In cases of vomiting or dyspnoea, the patient should be placed in a comfortable position with the lower limbs elevated.

Question 37

How should anaphylaxis be managed in the peri-operative period?

Answer 37

Maintain airway, give 100% oxygen and lie patient flat with legs elevated. Give epinephrine (adrenaline). This may be given intramuscularly in a dose of 0.5 mg to 1 mg (0.5 to 1 mL of 1:1,000) and may be repeated every 10 min according to the arterial pressure and pulse until improvement occurs.