Anaphylaxis in children

Surgical approach (if applicable)

Not an operation; management is resuscitation-focused. If occurring intra-operatively, the surgical team typically:
- Stops suspected trigger exposure (e.g. antibiotic infusion, latex contact, chlorhexidine prep).
- Ceases surgical stimulation temporarily; packs/controls bleeding to reduce confounders (haemorrhage vs anaphylaxis).
- Assists with positioning (supine, legs elevated) and rapid access (IV/IO), calls for help, fetches anaphylaxis box.
- If bronchospasm/airway swelling: pauses surgery to prioritise airway/ventilation; prepares for emergency airway/surgical airway if needed.

Anaesthetic management (contextual)

Type of anaesthesia: usually occurs during GA (also possible with sedation/regional; also community/ward).
Airway: if peri-operative, often already ETT; if not, early oxygenation/ventilation with bag-mask; consider early intubation if airway oedema/bronchospasm refractory.
Duration: event is minutes; resuscitation/ICU observation hours; biphasic reactions possible.
Pain: not a painful condition; distress from hypoxia/bronchospasm/hypotension; treat agitation as hypoxia until proven otherwise.

Definition and pathophysiology

Anaphylaxis: severe, life-threatening systemic hypersensitivity reaction with airway/breathing/circulation compromise ± skin/mucosal changes.
Mechanisms: IgE-mediated (classic) and non-IgE (direct mast cell activation, complement). Clinical management is the same initially.
- Mediators: histamine, tryptase, leukotrienes, prostaglandins → vasodilation, capillary leak, bronchospasm, mucosal oedema, myocardial depression.
Children: respiratory features (wheeze/stridor) may predominate; hypotension can be late and is a pre-terminal sign in some.

Common triggers (child + peri-operative)

Community/ED: foods (peanut/tree nut, egg, milk), insect stings, antibiotics (penicillins), idiopathic.
Peri-operative (UK pattern): antibiotics (e.g. co-amoxiclav/teicoplanin), neuromuscular blockers (rocuronium, suxamethonium), chlorhexidine, latex, dyes/gelatin colloids (less common), opioids (often non-IgE histamine release).
- Latex risk: spina bifida, multiple prior surgeries, urogenital anomalies, healthcare worker exposure.

Recognition: clinical features and grading

Airway: hoarse voice, stridor, tongue/lip swelling, difficulty swallowing, airway oedema.
Breathing: bronchospasm (wheeze, high airway pressures, poor compliance), hypoxia, tachypnoea.
Circulation: hypotension, tachycardia (or bradycardia late), poor perfusion, collapse, arrhythmias.
Skin/mucosa: urticaria, flushing, angioedema (may be absent in anaesthetised child).
GI: vomiting, abdominal pain (more in community presentations).
Intra-op clues: sudden hypotension, difficult ventilation/bronchospasm, increased airway pressures, desaturation, facial oedema, generalized erythema; consider differential diagnoses simultaneously.

Differential diagnoses (especially intra-operative)

Haemorrhage/hypovolaemia; high neuraxial block; tension pneumothorax; bronchial intubation; circuit obstruction/kink; aspiration; pulmonary embolism/air embolism; myocardial ischaemia/arrhythmia; malignant hyperthermia (later hypercapnia/rigidity); sepsis; vasovagal event.
- Key discriminator: rapid onset after exposure to drug/latex/chlorhexidine + bronchospasm/urticaria/angioedema supports anaphylaxis.

Immediate management (peri-operative/anaesthetic setting)

Call for help; declare anaphylaxis; allocate roles; bring anaphylaxis box and dosing chart.
Stop suspected trigger(s): stop antibiotic/infusion, remove latex source, stop chlorhexidine exposure; maintain anaesthesia with agents least likely to worsen hypotension (e.g. volatile at low dose, opioids cautiously).
Airway/Breathing: 100% O2; hand ventilate to assess compliance; deepen anaesthesia if bronchospasm; consider early intubation if not already secured and airway oedema suspected.
- Bronchospasm: salbutamol via MDI/spacer in circuit or nebulised; consider ipratropium; consider IV magnesium (specialist/ICU setting).
Circulation: lie flat, legs elevated; large-bore IV/IO access; start rapid crystalloid boluses 10–20 mL/kg, repeat as needed (capillary leak).
Adrenaline is first-line.
- If peri-arrest/severe hypotension/poor perfusion: give IV adrenaline titrated in small boluses (e.g. 0.5–1 microgram/kg boluses) and start infusion early (e.g. 0.05–0.5 microgram/kg/min, titrate). Use local paediatric/RCUK/Association of Anaesthetists guidance.
- If not in theatre/IV access not reliable: IM adrenaline 10 microgram/kg (max 500 microgram) into anterolateral thigh; repeat every 5 minutes if needed.
If cardiovascular collapse: follow paediatric ALS; continue adrenaline, high-quality CPR, treat reversible causes.
Second-line/supportive drugs (do not delay adrenaline):
- Antihistamine: chlorphenamine IV (age/weight-based).
- Steroid: hydrocortisone IV (age/weight-based). Helps reduce protracted/biphasic symptoms; not immediate life-saving.
- Vasopressors/inotropes: noradrenaline/vasopressin may be needed in refractory vasoplegia (ICU/theatre).
- Glucagon: consider if on beta-blocker (rare in children) and refractory to adrenaline (specialist setting).
Continue monitoring: ECG, NIBP/arterial line, SpO2, ETCO2; consider ABG/lactate; temperature; urine output.
Decision to proceed with surgery: usually abandon/postpone unless life-saving; document rationale and communicate with team/parents.

Adrenaline: practical points for paediatric anaesthesia

Aim: restore perfusion and relieve bronchospasm (α1 vasoconstriction, β1 inotropy/chronotropy, β2 bronchodilation/mast cell stabilisation).
IV boluses should be small and titrated with close monitoring; avoid large “adult-style” boluses which risk arrhythmias and severe hypertension once circulation returns.
Early infusion is often safer than repeated boluses when ongoing vasoplegia persists.

Investigations and documentation (peri-operative anaphylaxis)

Bloods: mast cell tryptase
- Take as soon as feasible after resuscitation (ideally within 1–2 h), then at 4–6 h, and a baseline sample at ≥24 h (or at follow-up) for comparison (local policy varies).
- Normal tryptase does not exclude anaphylaxis (especially food-related or isolated bronchospasm).
Record a clear timeline: all drugs/fluids/blood products/antiseptics/latex exposures with times; onset of signs; vitals; treatment doses and response.
Report via local critical incident system; refer to specialist allergy clinic experienced in anaesthetic reactions.

Post-event care and disposition

Observe for biphasic/protracted reactions; duration depends on severity and response (severe reactions often need HDU/ICU).
Provide discharge advice (if community/ED): trigger avoidance, adrenaline auto-injector training if indicated, written action plan, referral to allergy services.
For peri-operative cases: issue an anaesthetic alert letter; update electronic records; ensure future anaesthetics planned with allergy results and avoidance strategy.

Prevention and planning for future anaesthesia

Risk stratify: previous reaction, latex risk groups, multiple drug allergies (often non-specific), mastocytosis (rare).
Avoid known/suspected triggers until investigated; use latex-free environment if risk or previous latex reaction.
Premedication with antihistamines/steroids does not reliably prevent IgE-mediated anaphylaxis; do not use as substitute for avoidance and preparedness.
Have weight-based dosing readily available; ensure adrenaline infusion preparation knowledge; rehearse team response (simulation).

You are anaesthetising a 4-year-old for appendicectomy. Two minutes after IV co-amoxiclav the child becomes hypotensive and difficult to ventilate with wheeze. Talk me through your immediate management.

Structured A–E with early adrenaline, stop trigger, fluids, and escalation.

Call for help; declare anaphylaxis; stop antibiotic and any potential triggers; ask surgeon to pause.
100% oxygen; hand ventilate; check for mechanical causes (tube/circuit/bronchial intubation) while treating presumptively.
Adrenaline: if severe hypotension/poor perfusion under GA, give small IV boluses titrated (e.g. 0.5–1 microgram/kg) and start an infusion early if ongoing instability.
Rapid crystalloid bolus 10–20 mL/kg, repeat; consider arterial line once stabilising.
Treat bronchospasm: salbutamol via circuit/nebuliser; deepen anaesthesia; consider ipratropium/magnesium in refractory cases.
Second-line: chlorphenamine IV + hydrocortisone IV (do not delay adrenaline).
Decide on abandoning surgery unless immediately life-saving; arrange HDU/ICU; take tryptase samples and document timeline.

How do you distinguish anaphylaxis from other causes of sudden collapse under anaesthesia in a child?

Use pattern recognition + exclusions; treat first when uncertain.

Temporal relationship to exposure (antibiotic/NMBA/chlorhexidine/latex) with rapid onset supports anaphylaxis.
Bronchospasm with rising airway pressures + desaturation; skin flushing/urticaria/angioedema (may be absent).
Exclude mechanical/anaesthetic causes quickly: tube obstruction/kink, bronchial intubation, circuit disconnection, aspiration, tension pneumothorax.
Consider haemorrhage/hypovolaemia, high spinal, arrhythmia, air embolism, sepsis; use surgical field assessment, ETCO2 trends, and response to adrenaline/fluids.

What are the common peri-operative triggers of anaphylaxis in children in the UK, and how would you reduce risk?

Know the big four and practical avoidance steps.

Common triggers: antibiotics, NMBAs, chlorhexidine, latex.
Risk reduction: confirm allergy history; avoid known culprit; latex-free setup for high-risk children; consider alternative skin prep if chlorhexidine concern; give antibiotics with monitoring and clear timing.
Preparedness: weight-based adrenaline guidance available; team brief; immediate access to IV/IO and infusion pumps.

Discuss adrenaline dosing routes in paediatric anaphylaxis and when you would choose IM vs IV.

Route depends on setting, access, and severity.

IM adrenaline is first-line in community/ward/ED when IV access is absent or delayed: 10 microgram/kg (max 500 microgram) to anterolateral thigh; repeat every 5 min if needed.
In theatre with secured airway, monitoring, and reliable IV access, severe hypotension/bronchospasm may need titrated IV adrenaline boluses and early infusion.
Avoid large IV boluses; use small increments with close haemodynamic monitoring to reduce arrhythmia risk.

What blood tests would you send after suspected peri-operative anaphylaxis, and how do you interpret them?

Tryptase strategy and limitations are key viva points.

Send mast cell tryptase: early sample (as soon as feasible after resuscitation, ideally within 1–2 h), a later sample (e.g. 4–6 h), and a baseline at ≥24 h or at follow-up.
Interpretation: rise from baseline supports mast cell activation; normal tryptase does not exclude anaphylaxis.
Ensure detailed documentation of exposures and timings to support later allergy testing (skin tests/specific IgE) in a specialist clinic.

The child remains hypotensive despite repeated adrenaline boluses and 40 mL/kg crystalloid. What are your next steps?

Think ongoing vasoplegia, infusion, additional vasopressors, and alternative diagnoses.

Start/uptitrate adrenaline infusion; secure arterial line and central/second large-bore access if possible.
Consider additional vasopressors for refractory vasoplegia (e.g. noradrenaline; vasopressin in ICU/theatre protocols).
Reassess diagnosis and contributing factors: ongoing bleeding, tension pneumothorax, myocardial dysfunction/arrhythmia, anaphylactoid vs anaphylaxis; check ETCO2, echo if available, surgical field.
Escalate to PICU early; continue supportive care and monitoring; ensure tryptase sampling and incident reporting.

How would you manage suspected latex anaphylaxis in a child with spina bifida undergoing surgery?

Latex avoidance and theatre logistics are commonly examined.

Immediate management as per anaphylaxis algorithm (adrenaline, oxygen, fluids, stop exposure).
Remove latex sources: gloves, catheters, drains, elastic bands; switch to latex-free alternatives.
For future: schedule in latex-free theatre/session; latex-free equipment list; clear alerts on records; allergy referral for confirmation and cross-reactivity counselling.

What advice would you give parents after a peri-operative anaphylaxis event in their child?

Communication, safety-netting, and future planning.

Explain suspected anaphylaxis, treatments given, and that the exact trigger may be uncertain initially.
Outline investigations: tryptase results and referral to specialist allergy clinic for definitive testing and safe alternative agents.
Provide written documentation/alert letter listing suspected agents and those given safely; advise to present this for any future healthcare contact.
Discuss observation for recurrence (biphasic reaction) and when to seek urgent help.