QuestionSBA
QuestionChoice
This is the correct answer. The patient is experiencing anaphylaxis and therefore, requires IM adrenaline urgently. Note that the correct concentration for IM adrenaline is (1:1000) compared to IV adrenaline (1:10000) which is used during a cardiac arrest. The more concentrated form is therefore, the form that is injected into muscles whereas it would be inadvisable to inject such a dose directly into the vasculature
32843
a
Adrenaline IM (1:1000) 500 micrograms
QuestionChoice
IV adrenaline is not given during anaphylaxis unless it is performed by a specialist. This will usually require continuous monitoring
32846
d
Adrenaline IV (1:10000) 500 micrograms
QuestionChoice
This is incorrect. The concentration of adrenaline is for an IV dose
32844
b
Adrenaline IM (1:10000) 500 micrograms
QuestionChoice
IV adrenaline is not given during anaphylaxis unless it is performed by a specialist. This will usually require continuous monitoring
32847
e
Adrenaline IV (1:100000) 500 micrograms
QuestionChoice
IV adrenaline is not given during anaphylaxis unless it is performed by a specialist. This will usually require continuous monitoring. (Also, this concentration of adrenaline would be inadvisable to administer IV)
32845
c
Adrenaline IV (1:1000) 500 micrograms
Concept
Chapter
# Summary

Anaphylaxis is a medical emergency which often occurs due to a type 1 IgE mediated hypersensitivity reaction to an allergen. It is characterised by the rapid onset of life-threatening airway swelling, bronchospasm and/or circulatory dysfunction. In most cases skin or mucosal changes are also present. Triggers include medications (such as penicillins), foods (such as peanuts) and insect stings. Diagnosis is clinical, with repeated mast cell tryptase levels a useful way to confirm the diagnosis in retrospect.  Management strategies include removing the trigger, ABCDE assessment, oxygen administration, and adrenaline administration, amongst other interventions. 
 
# Definition
 
Anaphylaxis is a rapid onset syndrome of life-threatening airway, breathing or circulatory dysfunction. An immunological reaction occurs when patients are exposed to allergens such as medications, foods (such as peanuts or eggs) and bee or other insect stings. Many cases of anaphylaxis however are idiopathic with no known trigger, or may be mediated by other mechanisms other than the classical type 1 IgE-mediated pathway. 

# Epidemiology
 
Approximately 1 in 1333 people in England have had an episode of anaphylaxis. There are approximately 20-30 deaths per year in the UK, with around half of these being iatrogenic (e.g. due to penicillin).
 

# Aetiology
 
Common precipitants of IgE-mediated allergic anaphylaxis include:

- Insect stings
- Nuts
- Other foods such as eggs or milk
- Latex
- Antibiotics (e.g. penicillins)
- Intravenous contrast agents
- Other medications (such as NSAIDs)
 

# Signs and Symptoms

Signs and symptoms are sudden in onset and progress rapidly. To be classed as anaphylaxis, patients need to have life-threatening problems affecting the:

- **Airway** (pharyngeal or laryngeal oedema)
    - Symptoms include difficulty swallowing and breathing, feeling that the throat is closing
    - Signs include stridor, hoarse voice and swelling of the tongue and lips
- **Breathing** (bronchospasm)
    - Symptoms include difficulty breathing, wheeze and cough
    - Signs include increased work of breathing and respiratory distress, hypoxaemia may cause confusion and cyanosis
    - Patients may fatigue leading to respiratory arrest
- **Circulation** (anaphylactic shock)
    - Symptoms include dizziness
    - Signs include pallor, clamminess, tachycardia and hypotension
    - Patients may develop arrhythmias and anaphylaxis can lead to cardiac arrest

Continuing with an A to E approach, the following signs and symptoms are often also seen:

- **Disability** (altered neurological state)
    - Symptoms include anxiety and a "sense of impending doom"
    - Signs include confusion, agitation and loss of consciousness
- **Exposure** (skin and mucosal changes)
    - These range from mild erythematous patches to florid generalised rashes
    - Often occur prior to the onset of other symptoms
    - Urticaria (hives) are itchy and can occur anywhere on the skin
    - Angioedema involves swelling of the eyelids and lips (as well as the tongue and throat causing airway obstruction)

**Gastrointestinal** manifestations including abdominal pain, incontinence and vomiting are also commonly seen in cases of anaphylaxis.
 
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# Differential Diagnosis

- **Life-threatening asthma exacerbation** 
    - Several overlapping features e.g. bronchospasm, tachycardia, reduced levels of consciousness
    - May cause raised mast cell tryptase also 
    - Triggers can be similar to anaphylaxis triggers
    - Would not have features of upper airway obstruction e.g. stridor or mucosal/skin changes e.g. urticaria
- **Other causes of angioedema** 
    - e.g. hereditary angioedema, induced by medications e.g. ACE inhibitors
    - Both involve histamine and/or bradykinin mediators
    - No circulatory dysfunction and shock unlike in anaphylaxis
- **Panic attack** 
    - May have tachycardia and tachypnoea accompanied by anxiety and feelings of doom, skin flushing may also occur
    - No signs of airway obstruction or circulatory collapse and symptoms often resolve with reassurance
- **Vasovagal episode** 
    - May occur after triggers e.g. vaccination
    - Mimic features of pallor and loss of consciousness
    - No airway or breathing symptoms unlike in anaphylaxis
 
# Investigations
 
Anaphylaxis should be diagnosed clinically based on the above features.

The following investigations should be carried out in the emergency setting:

- **ECG** - to look for myocardial ischaemia and arrhythmias which may be caused by anaphylaxis
- **Arterial blood gas** should be considered in hypoxic patients, may show metabolic acidosis due to shock
- **Bloods for mast cell tryptase** - the first sample should be taken as soon as possible after starting emergency treatment, with a second sample taken within 1 to 2 hours (no later than 4 hours from symptom onset) and a third sample taken after complete recovery (as a baseline)

An elevated serum tryptase from baseline is a useful confirmatory test for anaphylaxis especially where there is diagnostic uncertainty, although a normal level does not exclude anaphylaxis. 
 

# Management

**Emergency management:**
 
- Early recognition is key - call for help (put out a medical emergency call if in hospital)
- Remove any ongoing trigger e.g. stop causative medication, remove insect stinger
- Lie patient flat and elevate legs if hypotensive, or help to a seated position to aid breathing
- Give intramuscular adrenaline - 0.5ml of 1:1000 (500mcg) in adults, usually into the anterolateral thigh
- Secure the airway
- Administer high flow oxygen and ensure monitoring in place (oxygen saturations, blood pressure and ECG)
- Consider inhaled bronchodilators (salbutamol or ipratropium) for wheeze
- Give an IV fluid bolus in patients with hypotension or shock, or who do not respond to the initial adrenaline dose
- IM adrenaline can be repeated after 5 minutes if no response
- In the case of a cardiac arrest, start CPR and give further adrenaline via the IV or IO route (as intramuscular administration is unreliable in this scenario)

**Once stabilised:**

- Give an non-sedating oral antihistamine (e.g. 10-20mg cetirizine) - if not able to swallow can give IV or IM chlorphenamine 
    - This helps to treat cutaneous symptoms of anaphylaxis but is not a first-line treatment as they do not treat life-threatening features
- Steroids are no longer routinely advised but may be considered in patients with an asthma exacerbation/anaphylaxis overlap or in cases of ongoing shock
- Observe patients for a **biphasic reaction** (when symptoms of anaphylaxis reoccur without further exposure to a trigger)
    - This occurs in around 5% of patients
    - Patients with severe initial presentations, those who require multiple adrenaline doses or who had a delay in treatment are at increased risk
    - Patients should be risk stratified - those at the lowest risk can be discharged after 2 hours of observation, those at intermediate risk should be observed for at least 6 hours and those at the highest risk for at least 12 hours
- Prior to discharge, patients and families should be educated about anaphylaxis, what actions to take and the risk of a biphasic reaction
    - Give two adrenaline auto-injectors (e.g. an EpiPen) and demonstrate how to use these
    - Advise on trigger avoidance
- Refer for follow up in a specialist allergy service

# NICE Guidelines

[NICE - Anaphylaxis: assessment and referral after emergency treatment](Anaphylaxis: assessment and referral after emergency treatment)

[NICE CKS - Angio-oedema and Anaphylaxis](https://cks.nice.org.uk/topics/angio-oedema-anaphylaxis/)

# References
 
[UK Resuscitation Council Anaphylaxis Guidelines](https://www.resus.org.uk/library/additional-guidance/guidance-anaphylaxis/emergency-treatment)
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Angioedema seen in someone with anaphylaxis.
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Quesmed Tutorial: Paediatric Peri-arrest and Emergencies
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Anaphylaxis is a severe, life-threatening allergic reaction treated with intramuscular (IM) adrenaline (1:1000) at a dose of 500 micrograms to rapidly counteract symptoms by stimulating alpha and beta-adrenergic receptors
A 44-year-old female attends A&E after developing sudden onset breathing difficulties. Her lips are swollen and she has developed a widespread pruritic rash.

Which is the correct prescription?
a