Anaphylaxis

Question 1

Define anaphylaxis

Answer 1

Acute, severe, generalised or systemic, hypersensitivity reaction that is characterised by rapidly developing life-threatening airway and/or breathing and/or circulation problems

Question 2

What are the causes of anaphylaxis

Answer 2

In children, 85% due to food allergy (and most are in those <5yo)

Foods (1-3/-1/2) e.g. peanuts
Drugs e.g. penicillin, NSAIDs, anaesthesia, opioids
Insect stings e.g. wasps and bees
Latex
Contrast agents

Can require a co-factor e.g. NSAIDs, alcohol, another food, exercise to provoke anaphylaxis

Question 3

What are the symptoms of anaphylaxis

Answer 3

Acute onset of symptoms on exposure to allergen (minutes to an hour)

SOB, sensation of choking
Inspiratory stridor (“Wheeze”) and hoarse voice
Swelling of lips and face
Pale, clammy skin
Urticaria, erythema, pruritus
Confusion or disorientation
Nausea, vomiting, diarrhoea, incontinence
Abdominal cramps and pain
Agitation, anxiety, sense of doom

Question 4

What is a biphasic reaction

Answer 4

A two phase anaphylactic event.
Symptoms/anaphylaxis returns without re-exposure to the allergen.
The second reaction can be less severe, equal to or more severe than the first reaction.
occur 1-72h after the first reaction in up to 20% of patients

Question 5

What are the signs of anaphylaxis on examination

Answer 5

Obs: tachypnoea, tachycardia, hypotension
General: cyanosis, pallor, clammy, orofacial swelling, rhinitis, conjunctivitis, urticaria, erythema, reduced consciousness
Respiratory: wheeze, inspiratory stridor, hoarse voice, accessory muscle use, hyperinflation

Question 6

What are the signs of anaphylaxis on A-E assessment

Answer 6

Airway: swelling, hoarseness, stridor
Breathing: high RR, wheeze, cyanosis, SpO2 <92%, confusion
Circulation: pale, clammy, low BP
Disability: drowsy, coma
Skin: urticaria/angioedema

Question 7

What investigations should be done for anaphylaxis

Answer 7

CLINICAL DIAGNOSIS → treat immediately

Bedside: ECG
Bloods: ABG, U&Es, mast cell tryptase
Other: CXR

Question 8

What is the management for anaphylaxis without cardiorespiratory arrest

Answer 8

1. A-E assessment + call for help
2. Position patient
3. Adrenaline IM (anterolateral middle 1/3 thigh)
   
   • Adults: 0.5 mg IM
   • Repeat at 5 min intervals according to response
4. Establish airway + high flow oxygen
5. IV fluids 20ml/kg
6. Serial re-assessment (sats, ECG, BP)

Consider chlorphenamine (IM or slow IV), Hydrocortisone (IM/slow IV), nebulised salbutamol for wheeze

Question 9

What are the doses of adrenaline for anaphylaxis

Answer 9

1:1000

<6: 0.15 mg IM
6-12: 0.3 mg IM
>12 0.5 mg IM

Question 10

What positions should the patient be put in in anaphylaxis

Answer 10

Predominant airway/breathing problems: sit them up
Circulation problems: lie flat ± legs up
Unconscious: recovery position
Pregnant: on their left
Feels faint: Do NOT sit or stand them up

Question 11

What treatment should be given after an anaphylactic patient is made stable

Answer 11

1. Antihistamine e.g. Chlorphenamine
   a. <6: 2.5mg IM/IV
   b. 6-12: 5mg IM/IV
   c. >12: 10mg IV/IM
2. Corticosteroid i.e. hydrocortisone
   a. <6: 50mg IV/IM
   b. 6-12: 100mg IM/IV
   c. >12: 200mg IV/IM
3. Monitor for biphasic reaction (6-12 hours)
4. Take serum tryptase level if there is uncertainty about anaphylaxis

Question 12

What is the prognosis for anaphylaxis

Answer 12

Outcome is very dependent: success of therapy, time of diagnosis, co-morbidities, age
Severity of previous reactions does NOT predict the severity of future reactions
Individuals with previous reactions are at higher risk for recurrence
1 in 1,000 are fatal (mostly in adolescents when concerning food)