Moderate to severe croup: dexamethasone and nebulised adrenaline
The case
A 2-year-old boy is brought to the emergency department at 2 am with a 24-hour history of a hoarse, barking cough and progressively noisy breathing after 2 days of mild coryza. Tonight he developed persistent inspiratory stridor at rest, marked intercostal and subcostal recession, and agitation. He is not drooling, can swallow, and has not vomited. He is fully immunised. Heart rate is 150/min, respiratory rate 48/min, oxygen saturation 94% in room air and temperature 37.8°C. Air entry is good bilaterally with occasional transmitted wheeze. White cell count is 9.5 × 10^9/L and CRP 8 mg/L. Arterial blood gas on room air: pH 7.33, pCO2 6.8 kPa, pO2 10.5 kPa. He has never been admitted to hospital. What is the single best next step in management?
Options
- ANebulised adrenaline (epinephrine) plus oral dexamethasone
- BHeliox, then discharge if improved
- CNebulised salbutamol and observe
- DAdmit for intramuscular benzylpenicillin
- EImmediate intubation without a trial of treatment
Think it through before you read on. Which single option is best, and why are the other four wrong?
Show the answer and explanation
Answer
A. Nebulised adrenaline (epinephrine) plus oral dexamethasone
Why this is the right answer
Croup (laryngotracheobronchitis) is a viral infection, usually parainfluenza, that causes swelling below the vocal cords. The result is a barking cough, a hoarse voice and inspiratory stridor. It is commonest between 6 months and 3 years and is worst at night.
Severity is judged clinically, not by tests. Stridor at rest with marked recession and agitation is moderate to severe croup. The mild hypercapnia on the gas supports this, but a blood gas is not normally needed and the distress of taking it can worsen the obstruction.
Corticosteroids are the core treatment for all croup severe enough to present to hospital. A single oral dose of dexamethasone (0.15 to 0.6 mg/kg; most Australian centres use 0.15 mg/kg, maximum 12 mg) reduces airway swelling within a few hours and reduces admission and return visits. Oral prednisolone is an alternative.
In moderate to severe croup, nebulised adrenaline (epinephrine) is added for rapid, temporary relief. It constricts mucosal blood vessels and reduces oedema within minutes, but the effect wears off after 1 to 2 hours, so the child must be observed for at least 2 to 4 hours afterwards to watch for rebound. The Royal Children's Hospital guideline sets out this approach. Keep the child calm on a parent's lap; distress worsens the obstruction.
Epiglottitis and bacterial tracheitis are the dangerous mimics. This child has no drooling, no dysphagia, no toxic appearance and is fully immunised against Haemophilus influenzae type b, so they are unlikely.
Why the other options are wrong
- B
Heliox is an adjunct in severe cases, and discharging a child with stridor at rest is unsafe.
- C
Salbutamol treats lower airway bronchospasm, not subglottic oedema.
- D
This is viral croup; there is no drooling, toxicity or consolidation to suggest a bacterial cause.
- E
He is alert, oxygenating and compensating; intubation is for impending respiratory failure after treatment fails.
High-yield takeaway
Croup with stridor at rest: oral dexamethasone plus nebulised adrenaline, keep the child calm, and observe for at least 2 to 4 hours after the adrenaline.
Reference: Royal Children's Hospital Melbourne Clinical Practice Guideline: Croup (Laryngotracheobronchitis) (2023)
Common questions
How long should a child be observed after nebulised adrenaline?
At least 2 to 4 hours, because the effect wears off and the stridor can return.
What features suggest epiglottitis rather than croup?
Drooling, difficulty swallowing, a toxic appearance, sitting forward, a muffled voice, and no barking cough.
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