Anaphylaxis (Resp)

Question 1

Define anaphylaxis

Answer 1

It is a severe systemic Type 1 IgE-mediated hypersensitivity (allergic) reaction that is rapid in onset and may cause death.
It is a life threatening medical emergency.

Question 2

List the features of anaphylaxis definition

Answer 2

Severe, life threatening type 1 hypersensitivity reaction.
IgE-mediated
Rapid onset + systemic.
Occurs when exposed to certain precipitants.

Question 3

Give examples of what could cause anaphylaxis

Answer 3

Precipitants that can cause anaphylaxis in certain individuals include:
Medications e.g. ABs like penicillin, NSAIDs
Certain foods (e.g. peanuts and eggs)
Bee or other insect stings

Question 4

Describe the first stage of the pathophysiology of anaphylaxis

Answer 4

Sensitisation phase
1. First exposure to allergen either by ingestion, inhalation, skin contact etc.
2. Dendritic cells will process and present them to naive T cells which will differentiate into Th2 cells in response to IL-4 (cytokine given by eosinophils, basophils etc but not from the DC that much)
3. B cells then internalise and present the allergen to the Th2 cells which produce IL-4 to the B cells (also release IL-5,13)
4. This causes B cells to class switch from IgG to IgE producing B cells
5. These allergen specific IgE antibodies diffuse throughout the body and bind to high affinity receptors (FcεRI) on mast cells and basophils via Fc, leaving their Fab exposed and free for the allergen.
6. This sensitises the cells to the allergen, so upon next exposures they will react

Question 5

Describe the second stage of the pathophysiology of anaphylaxis

Answer 5

Effector phase
1. Upon second exposure to the same allergen, it binds to and cross links IgEs on the Mast Cells and basophils
2. This triggers the release of pro inflammatory mediators from the cells known as degranulation
4. The main IMs released are histamine, tryptase, LTs, PGs.
5. These cause: vasodilation, increased vascular permeability, smooth muscle contraction, and mucus secretion, leading to the clinical manifestations of anaphylaxis.

Question 6

What is the biphasic reaction in hypersensitivity reactions/anaphylaxis?

Answer 6

This describes the recurrence of anaphylaxis symptoms soon after the initial episode.
It happens in about 5% of pts (~12 hrs after but may occur over 24 hours after). It is usually less severe.
Main cell is eosinophils degranulating.
a.k.a late-phase reaction

Question 7

What are the risk factors of anaphylaxis?

Answer 7

History of anaphylaxis
Atopy (genetic tendency to develop allergic diseases) tf so if diagnosed with Asthma, atopic dermatitis etc.
Family history

Question 8

What are the risk factors for a biphasic reaction?

Answer 8

Severe initial presentation
More than one dose of adrenaline required
Delay in giving adrenaline (>30-60 minutes from initial symptoms)

Question 9

What are the clinical features of anaphylaxis?

Answer 9

Skin reactions: widespread urticaria, itching, flushed skin

Respiratory symptoms: swollen tongue/lips, sneezing, wheezing

GIT symptoms: abdominal pain, nausea, vomiting, diarrhoea

Tachycardia
Hypotension

Question 10

How is anaphylaxis diagnosis confirmed - investigation?

Answer 10

This is by measuring the serum levels of mast cell tryptase.

However, this is done after the patient is stabilised.

Question 11

How is anaphylaxis recognised - (+ list the symptoms)?

Answer 11

ABCDE approach/assessment

Airway problems - throat and tongue swelling (leading to a hoarse voice and stridor)
Breathing - resp wheeze, dyspnea
Circulation - hypotension, tachycardia
Disability - confusion or agitation as ABC can lead to altered neurological status
Exposure - skin or mucosal changes e.g. widespread erythema, urticaria, itchy, or angioedema (often first features, in about 80%)

However, just skin or mucosal changes without ABC does not suggest an anaphylactic reaction.

Question 12

How is suspected anaphylaxis managed - emergency management?

Answer 12

Urgent ABCDE assessment
Call for help (e.g. 999, resus team)
Remove trigger and position patient - lay flat with/without legs raised. Lie left side if pregnant
Give IM adrenaline. If no response, repeat IM adrenaline after 5 minutes. Keep doing until improvement.
High flow O2 and monitoring (pulse oximetry, ECG, BP)
If the patient is hypotensive/shock - do IV fluid challenge using crystalloid.

Question 13

How is IM adrenaline administered in anaphylaxis?

Answer 13

Injected at anterolateral aspect of middle third of the thigh

Question 14

What is the management after the patient is stabilised in anaphylaxis?

Answer 14

May give anti histamines to help skin symptoms - this used to be part of initial management, but NOT anymore (done once stabilised via adrenaline/IV fluids)

Patients should be monitored for 6-12 hours after the initial presentation in case of a rebound episode (Biphasic reaction)

All pts with a new diagnosis should be referred to a specialist allergy clinic

Patients should be prescribed 2 adrenaline auto-injectors and trained how to use it

Question 15

List the types of patient discharge in anaphylaxis (after management)?

Answer 15

Fast track discharge - discharge after 2 hours observation from anaphylaxis resolution
Discharge minimum 6 hours ‘’
Discharge minimum 12 hours ‘’

Question 16

When is fast track discharge done in anaphylaxis?

Answer 16

Patients can be discharged 2hrs after symptom resolution if:

• good response within 5-10 mins to a single dose of adrenaline
• complete resolution of symptoms
• pt has been given an adrenaline auto-injector and is trained how to use it
• adequate supervision following discharge

Question 17

When is discharge after 6 hours done for pt with anaphylaxis?

Answer 17

Patients can be discharged 6hrs after symptom resolution if:

2 doses of IM adrenaline needed
OR
previous biphasic reaction

Question 18

When is patient discharged only after a minimum of 12 hours after resolution in anaphylaxis?

Answer 18

Patients can be discharged 12hrs after symptom resolution if:
- severe reaction requiring > 2 doses of IM adrenaline
- patient has severe asthma
- possibility of an ongoing reaction/continuing allergen absorption (e.g. slow-release medication)
- patient presents late at night
- patient is in areas where access to emergency access care may be difficult

Question 19

What is refractory anaphylaxis and how is it managed?

Answer 19

Refractory anaphylaxis is defined as respiratory and/or cardiovascular problems persistdespite 2 doses of IM adrenaline

• IV fluids should be given for shock/hypotension
• Experts should considerIV adrenaline infusion

Question 20

What are the differentials of anaphylaxis?

Answer 20

Acute asthma attack
Other types of shock (usually lacks the specific allergic symptoms e.g. itching)
Angioedmea
Panic attack

Question 21

What are the complications of anaphylaxis?

Answer 21

Biphasic reaction
Refractory anaphylaxis