Anaphylaxis prevention, action plans and autoinjectors — branching viva

Opening question

Examiner: Take me through this boy. What is your frame for the prevention prescription, and what are you going to write today? [1]

Candidate: My frame is that a child at risk of anaphylaxis is kept alive by a package, not by a single intervention, and the visit today is about building that package so it travels with him. He has had a confirmed anaphylactic reaction to peanut, so he is at risk of recurrence, and my job is to make sure that the next reaction is survivable wherever it happens. The package has six components: confirmed trigger avoidance, the green and red ASCIA action plans, the weight-appropriate adrenaline autoinjector, two devices and a trainer, rehearsed education of every carer, and optimised asthma control with a review date. I am going to write all six today, because any one of them alone is insufficient. [10]

Examiner: Why two plans rather than one? [10]

Candidate: Because the decision the plan exists to make is when to cross from a mild reaction to anaphylaxis, and the colour coding removes that deliberation at the moment of crisis. The green plan covers mild-to-moderate reactions — skin and mild gut symptoms — where the carer gives an antihistamine and watches closely for escalation. The red plan triggers adrenaline the moment anaphylaxis is recognised: any airway or breathing problem, collapse or pallor, or a rapid reaction involving skin plus another body system. The carer does not diagnose; they read the colour, and that single design feature is what makes the plan usable under stress by a non-clinician. [10]

Branch 1 — adrenaline pharmacology and the route

Examiner: Why adrenaline, and why intramuscularly into the outer thigh? [9]

Candidate: Adrenaline is the single drug that reverses every limb of the anaphylaxis cascade. Its alpha-1 agonism vasoconstricts, restoring blood pressure and shrinking the mucosal oedema that threatens the airway; its beta-1 agonism increases heart rate and contractility to restore cardiac output in shock; its beta-2 agonism bronchodilates; and it stabilises the mast cell to slow further mediator release. Antihistamines, steroids and bronchodilators are adjuncts — none reverses the acute haemodynamic collapse, and none saves a life in the first minutes. The intramuscular route into the vastus lateralis — the outer middle third of the thigh — gives the fastest and most reliable peak concentration, far faster and more predictable than subcutaneous injection, because absorption from subcutaneous tissue in a shock state is erratic and slow. The deltoid and the buttock are inferior sites. The autoinjector is engineered around this pharmacology. [9] [3]

Examiner: And the technique? [9]

Candidate: Remove the safety cap, place the orange end — the needle end — against the outer mid-thigh, push firmly until it clicks, hold for three seconds, remove and massage. It can be given through clothing, which removes a reason for delay. The mnemonic 'blue to the sky, orange to the thigh' encodes the orientation so the needle enters the child rather than the thumb. I teach and rehearse this with a trainer device, because technique decays, and a family shown the device once at diagnosis will not reliably reproduce it a year later. [9] [10]

Branch 2 — the weight-band dosing decision

Examiner: This boy weighs 23 kg. Which device does he need, and why does that matter? [10]

Candidate: At 23 kg he is at or above the ASCIA 20 kg cut-off, so he needs the 0.3 mg device (EpiPen or Anapen 300), not the 0.15 mg junior device. The 0.15 mg device is for children 7.5 to 20 kg, and the 0.5 mg device for 50 kg and over where it is available. The reason this matters — and it is the single most tested paediatric anaphylaxis fact — is that a child who has grown past 20 kg and is still carrying a junior device is carrying an underdose, and effectively has no device. So I check the weight at every visit, and I tell the family to do the same, because they will not raise it themselves. The moment he crosses 20 kg I up-titrate the dose. [10]

Examiner: How many devices do you prescribe? [10]

Candidate: Two — one for home and one for school — plus a trainer device for rehearsal. The second device matters for two reasons: it travels with the child into every setting, and it is the five-minute repeat dose if the first device does not work or the reaction recurs. The repeat-dose rule is a fixed part of the plan: a second device is given after five minutes if there is no response, and the ambulance is on its way. That is why an ambulance is called every single time, even after apparent recovery. [10]

Branch 3 — the biphasic reaction and observation

Examiner: He is sent to hospital after every community device use. Why? [12]

Candidate: Because of the biphasic reaction — a late recurrence of symptoms hours after the initial reaction has settled, driven by persistent mediator release and the long tissue half-life of leukotrienes. Lee and colleagues' systematic review and meta-analysis found that biphasic reactions occur in a small but real fraction of anaphylaxis presentations, typically within the first hours, and Mehr and colleagues identified the paediatric predictors — a severe initial reaction, the need for more than one dose of adrenaline, and a wide initial pulse pressure. The biphasic risk is the reason a second device is prescribed and the reason observation is mandatory. The child who looks fully recovered in the kitchen may relapse in the emergency department, and the observation window is the safety net that catches that relapse. [12] [13]

Examiner: So the disposition after a community device use is non-negotiable? [12]

Candidate: Yes. Ambulance transfer, stating anaphylaxis, and a period of hospital observation. The only deviation I would accept is if the ambulance crew and the receiving hospital jointly decide a shorter observation is safe, and even then the default is observe. I would not send a child home after a community device use, however well they look. [12]

Branch 4 — school readiness and the education ladder

Examiner: How do you make the school ready? [4]

Candidate: The school receives a copy of the red action plan and a device, a named staff member is confirmed as trained — in Australia that training is the ASCIA school program — storage is agreed to be accessible rather than locked away, and the response is rehearsed. The education ladder is where prevention lives or dies: I teach the parents, the child at an age-appropriate level, and the named school staff member, using a trainer device, and I re-teach at every visit. Technique decays, and the school staff member trained in term one may have moved on by term three. Label-reading and cross-contamination advice for peanut is part of the daily layer that makes the device a backup rather than a first resort. [4] [10]

Examiner: And his asthma? [11]

Candidate: I optimise it aggressively. He has asthma, and asthma plus food allergy is a recognised fatal-anaphylaxis pairing — uncontrolled asthma multiplies anaphylaxis fatality risk, and an allergic wheeze treated as asthma delays adrenaline. He moves onto a preventer with a written asthma action plan, and we rehearse the crossover scenario: a wheeze after an allergen is adrenaline first, salbutamol as adjunct. [11]

Branch 5 — the fatal-risk triad and the adolescent

Examiner: Now make him sixteen years old, with peanut anaphylaxis and uncontrolled asthma, who does not carry his device. What changes? [11]

Candidate: Everything about the plan, because he now sits in the classic fatal-anaphylaxis triad: adolescence, peanut or tree-nut allergy, and uncontrolled asthma. Turner and colleagues identified these as the recurring risk factors in fatal paediatric anaphylaxis, and the additional modifiable risk here is non-carrying of the device — an absent device cannot be used. The plan is rebuilt around his behaviour, not around his parents. I prescribe a device that travels with him — compact, kept somewhere he always carries — and a backup at home or school. The conversation confronts the non-carrying without stigma, framing the device as autonomy and freedom rather than restriction. I optimise his asthma, I counsel him on alcohol and eating out in a mental-health-aware way, and I hand him increasing autonomy over the action plan. The aim is a young person who carries the device, uses it, and tells someone — not a compliant child who relies on a parent who is no longer present. [11] [4]

Examiner: And the overarching principle, in one sentence? [9]

Candidate: Adrenaline is safer than withholding it — when anaphylaxis is possible, give it, because the harm of an unnecessary dose is small and reversible, and the harm of a missed dose is death. [9]