Paediatric asthma

Paediatric Acute Asthma

Asthma is the most common chronic respiratory disorder of childhood in Australia. Acute exacerbations result from acute airway smooth muscle bronchospasm, mucosal oedema, and hypersecretion of viscous mucus.

Preschool Wheeze Phenotypes (Children Under 5 Years)

1. Viral-Induced Wheeze (Episodic Wheeze): Wheezing episodes occur exclusively in association with acute viral upper respiratory tract infections, with complete absence of cough or wheeze between viral episodes. Usually resolves by early school age.
2. Multi-Trigger Wheeze: Wheezing occurs both during viral infections and in response to interval triggers (cold air, vigorous exercise, laughter, aeroallergens, emotional distress). Strongly linked to personal or family history of atopic eczema, allergic rhinitis, and elevated IgE; carries a high likelihood of persistent childhood asthma.

Acute Severity Assessment (Australian National Asthma Council Guidelines)

• Physical Activity: Mild / Moderate Exacerbation: Ambulatory, playful, alert; Severe Exacerbation: Agitated, prefers sitting upright; Life-Threatening Exacerbation: Lethargic, confused, exhausted
• Speech Capacity: Mild / Moderate Exacerbation: Speaks in sentences or phrases; Severe Exacerbation: Speaks only in single words; Life-Threatening Exacerbation: Unable to speak or cry
• Respiratory Rate: Mild / Moderate Exacerbation: Mildly to moderately increased; Severe Exacerbation: Markedly increased ($> 40\text{ to }50/\text{min}$); Life-Threatening Exacerbation: Tachypnoea or slow, gasping respirations
• Accessory Muscle Use: Mild / Moderate Exacerbation: Mild intercostal retractions; Severe Exacerbation: Marked sternal/subcostal retractions, tracheal tug; Life-Threatening Exacerbation: Paradoxical thoracoabdominal breathing
• Auscultation: Mild / Moderate Exacerbation: Moderate expiratory wheezing; Severe Exacerbation: Loud, widespread expiratory and inspiratory wheeze; Life-Threatening Exacerbation: "Silent chest" (minimal/absent air entry)

Stepwise Emergency Management Protocol

1. Inhaled Short-Acting Beta-2 Agonist (Salbutamol)

• Delivery Device: Pressurised metered-dose inhaler (pMDI) connected to a valved holding chamber (spacer) (with an appropriately fitted silicone mask for children under 4 years). Spacers deliver superior pulmonary lung deposition, fewer cardiovascular side effects (less marked tachycardia), and lower hospitalisation rates compared to jet nebulisers.
• Dosing Regimen:
  • Mild / Moderate: 2 to 6 puffs of salbutamol ($100\text{ mcg/puff}$). Administer one puff at a time into the spacer, with the child taking 4 normal tidal breaths through the mouthpiece before administering the next puff. Reassess after 20 minutes.
• Paediatric asthma: Follow the age-specific protocol for repeated salbutamol by pMDI/spacer, often six puffs under age six and 12 at age six or above in the acute pathway. Monitor response and consider early steroid and escalation for severe disease; IV bronchodilators require specialist monitored care.

2. Systemic Corticosteroids

• Oral Prednisolone: Initiated early within the first hour of emergency presentation for all children with moderate-to-severe exacerbations.
• Dose: $1\text{ to }2\text{ mg/kg}$ as a single oral dose (maximum single dose $50\text{ mg}$), continued once daily for 3 days. A 3-day course does not require dose tapering. For children unable to tolerate oral medication due to severe distress or vomiting, intravenous hydrocortisone ($4\text{ mg/kg}$ 6-hourly) or methylprednisolone ($1\text{ mg/kg}$ 12-hourly) is substituted.

3. Inhaled Anticholinergic (Ipratropium Bromide)

• For severe or refractory acute asthma, add ipratropium bromide ($250\text{ mcg}$ for children $< 6\text{ years}$, $500\text{ mcg}$ for children $\ge 6\text{ years}$) to salbutamol nebulisation every 20 minutes for up to 3 doses during the first hour. Ipratropium blocks muscarinic receptors, promoting synergistic bronchodilation.

4. Intravenous Second-Line Therapies (Severe / Life-Threatening)

When bronchospasm is refractory to maximal inhaled bronchodilators and systemic steroids:

• Intravenous Magnesium Sulfate: Administer $50\text{ mg/kg}$ IV (maximum $2\text{ g}$) infused over 20 minutes under continuous cardiac and blood pressure monitoring. Magnesium inhibits calcium influx into bronchial smooth muscle cells, inducing rapid relaxation.
• Intravenous Salbutamol Bolus / Infusion: Loading bolus of $15\text{ mcg/kg}$ IV over 10 minutes, followed by continuous infusion at $1\text{ to }5\text{ mcg/kg/min}$. Frequent monitoring of serum potassium is essential, as high-dose salbutamol drives potassium into cells, causing profound hypokalaemia and secondary cardiac arrhythmias.
• Intravenous Aminophylline: Phosphodiesterase inhibitor reserved for PICU-level refractory status asthmaticus; requires therapeutic drug monitoring to avoid toxicity (seizures, dysrhythmias).

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Reassess response rather than count puffs alone

A child who can no longer speak normally, becomes exhausted or has a quiet chest after substantial respiratory effort needs urgent escalation. Less wheeze can reflect critically reduced airflow rather than improvement. Record observations, work of breathing, air entry and response after each treatment cycle, and call senior/retrieval help early when severe. A spacer regimen is appropriate only while the child can use it effectively; respiratory failure requires another supported pathway. At discharge, review preventer use, inhaler/spacer technique, triggers, a written action plan and timely follow-up. A successful single bronchodilator dose does not settle the long-term plan.

Before discharging a child after an asthma attack, assess whether the family can use the spacer and recognise deterioration. A written action plan, appropriate preventer review and arranged follow-up address the next attack; transient improvement after salbutamol alone does not establish safe discharge.

Primary references (checked 7 October 2026): RCH croup; 2025 Australasian bronchiolitis guideline; ASCIA device availability.