Guidelines anaphylaxis

Question 1

What is anaphylaxis?

Answer 1

Anaphylaxis is a severe, life-threatening, generalised or systemic hypersensitivity reaction

Question 2

What is anaphylaxis characterized by?

Answer 2

It is characterised by rapidly developing airway and/or breathing and/or circulation problems, and is usually associated with skin and mucosal changes

Question 3

What are common causes of anaphylaxis?

Answer 3

• The most common allergens that cause anaphylaxis include food (e.g. peanuts, sesame, tree nuts, soy, shellfish, and cow’s milk—see Food allergy), drugs (e.g. antibacterials, aspirin and other NSAIDs, neuromuscular blocking drugs, chlorhexidine, contrast media, and vaccines), venom (e.g. insect stings), and latex
• Anaphylactic reactions may also be associated with additives and excipients in foods and medicines.
• Refined arachis (peanut) oil, which may be present in some medicinal products, is unlikely to cause an allergic reaction—nevertheless it is wise to check the full formula of preparations which may contain allergens.

Question 4

When is anaphylaxis more likely to happen when administering drugs?

Answer 4

In the case of drugs, anaphylaxis is more likely after parenteral administration

Question 5

Who is at higher risk of anaphylaxis?

Answer 5

• Certain patients may be at higher risk of anaphylaxis, either because of an existing comorbidity (such as asthma) or because of an increased likelihood of repeated exposure to the same allergen (such as those with venom or food allergies)
• Patient receiving drugs parenterally

Question 6

Management of anaphylaxis

Answer 6

1- Immediately call for an ambulance or the resuscitation team (MET call) and begin initial treatment for anaphylaxis.
2- Lay the patient flat (with or without legs raised) to aid in the restoration of blood pressure, or in a semi-recumbent position for patients with airway and breathing problems (and no evidence of cardiovascular instability) to make breathing easier, or in the recovery position for unconscious patients who are breathing normally;
3- Remove the trigger causing the anaphylactic reaction if possible (e.g. stopping the suspected drug or removing the stinger after an insect sting)
4a- Intramuscular adrenaline/epinephrine should be given as first line treatment for anaphylaxis.
4b- High-flow oxygen should be given as soon as it is available
4c- Establish monitoring: Pulse oximetry, ECG, blood pressure
4d- Establish airway, Wide bore cannula (Intravenous fluids should be given to patients with hypotension/shock, or if there is poor response to an initial dose of adrenaline/epinephrine)
- If there is doubt about the diagnosis, give intramuscular adrenaline/epinephrine and seek expert advice.
- Assess response to treatment by monitoring vital signs (such as blood pressure, pulse, respiratory function, and level of consciousness) and auscultate for wheeze.
- If response not satisfactory:
1- A repeat dose of intramuscular adrenaline/epinephrine should be given after a 5-minute interval if there is no improvement in the patient’s condition.
2- Give more fluids if needed
- Patients who have no improvement in respiratory and/or cardiovascular problems despite 2 appropriate doses of intramuscular adrenaline/epinephrine, should have their care escalated quickly (call critical care) and managed as having refractory anaphylaxis

Question 7

How should pregnant women be positioned when having an anaphylactic reaction?

Answer 7

Pregnant females should lie on their left side to prevent aortocaval compression.

Question 8

What does adrenaline do in anaphylactic reactions?

Answer 8

• Adrenaline/epinephrine provides physiological reversal of the immediate symptoms associated with hypersensitivity reactions.
• Circulatory shock (vasoconstriction + Increased heart contractility and heart rate)
• Bronchospasm and swelling: bronchodilation - decrease in mediator release and decrease in edema
• Alpha 1 facilitates vasoconstriction, decrease in edema, and increase in blood pressure
• Beta 2 facilitates bronchodilation and decreased mediator release
• Beta 1 facilitates increased HR and contractility

Question 9

Adrenaline dose in anaphylactic shock

Answer 9

In those above 12: 1 in 1000 0.5mg (0.5ml) IM repeated after 5 mins if needed
In those 6-12: 0.3mg
In those under 6: 0.15mg

Question 10

Signs of anaphylaxis:

Answer 10

A- Swelling face/lips/tongue, stridor
B- Tachypnoea, wheeze
C- Pale/Clammy, low bp, tachycardia
D- Drowsy/GCS <15
E- Rash/Urticaria
Clammy meaning: cool, moist, and usually pale

Question 11

What is stridor?

Answer 11

High pitched, whistling sound of the upper airways

Question 12

What is a wheeze?

Answer 12

• High or low pitched continuous sound (musical characteristic) caused by narrowing of airways, often expiratory and associated with long expiratory phase due to the narrowing
• Seen in asthma and copd
• High pitched sound like squeaking, while low pitch sound like moaning or snoring

Question 13

Injection site for adrenalin IM in anaphylaxis

Answer 13

Anterolateral aspect of middle third of the thigh

Question 14

Refractory anaphylaxis management

Answer 14

• Ensure dedicated peripheral IV or IO access
• Adrenaline infusion + IV fluid bolus (Note: repeat IM adrenaline every 5 minutes until infusion started)
• Consider second vasopressor or IV Salbutamol or IV aminophyline if adrenaline giving unsatisfactory respone
• Establish CVL and arterial cannulation
• If an intravenous infusion cannot be administered safely (e.g. due to a patient being outside a hospital setting), continue to give intramuscular adrenaline/epinephrine at 5-minute intervals while life-threatening cardiovascular and/or respiratory features persist

Question 15

Nebulised medication in anaphylaxis

Answer 15

• Nebulised adrenaline/epinephrine may be effective as an adjunct to treat upper airways obstruction caused by laryngeal oedema, but only after treatment with intramuscular adrenaline/epinephrine and not as an alternative.
• Inhaled bronchodilator therapy with salbutamol and/or ipratropium bromide with oxygen may also be considered for patients with persisting respiratory problems (persistent bronchospasm), but should not be used as an alternative to further treatment with adrenaline/epinephrine

Question 16

Nebulised adrenaline dose indication and dose in anaphylaxis

Answer 16

Partial obstruction, 5ml of 1mg/ml

Question 17

Antihistamines in anaphylaxis

Answer 17

• Antihistamines are not recommended as part of the initial emergency treatment of anaphylaxis.
• Following stabilisation of the patient, a non-sedating oral antihistamine such as cetirizine hydrochloride (in preference to chlorphenamine maleate) may be considered, especially in patients with persistent cutaneous symptoms (urticaria and/or angioedema).
• If oral administration is not possible, intramuscular or intravenous chlorphenamine maleate can be given

Question 18

Corticosteroids in anaphylaxis

Answer 18

• The routine use of corticosteroids for the emergency treatment of anaphylaxis is not recommended.
• Consider corticosteroids after initial resuscitation for refractory reactions or ongoing asthma/shock; corticosteroids must not be given preferentially to adrenaline/epinephrine.
• Corticosteroids should be given via the oral route where possible.

Question 19

Effects of adrenaline vs noradrenaline on systems

Answer 19

• Reflex bradycardia is phenomena that occurs when baroreceptors are stimulated due to increase in blood pressure (baroreceptor reflex), leading to bradycardia
• The baroreceptors in the carotid sinus sense this increase in blood pressure and relay the information to the cardiovascular centres in the medulla oblongata. In order to maintain homeostasis, the cardiovascular centres activate the parasympathetic nervous system. Via the vagus nerve, the parasympathetic nervous system stimulates neurons that release the neurotransmitter acetylcholine (ACh) at synapses with cardiac muscle cells. Acetylcholine then binds to M2 muscarinic receptors, causing the decrease in heart rate that is referred to as reflex bradycardia