Paediatric Acute Asthma

Introduction

• Chronic inflammatory disease of airways characterised by reversible airways obstruction and bronchospasm
• Often viral exacerbations in children
• If <12 months of age, consider bronchiolitis
• Pre-school wheezers may not respond well to bronchodilators and steroids are less effective
• 3.5% of all paediatric ED presentations

Differential diagnosis

• Chronic
  • Cystic fibriosis
  • Ciliary dyskinesia (Kartagener’s syndrome: situs inversus)
  • Immune deficiency
  • Bronchiectasis
  • Airway abnormalities

Asthma pattern

• Patterns
  • Infrequent episodic
  • Frequent episodic
  • Persistent

• Infrequent episodic asthma (IEA)
  • 70-75% of children
  • Isolated episodes lasting 1 day to 2 weeks, usually 6-8 weeks apart
  • Typically viral or environmental allergen exposure
  • Asymptomatic in interval
  • Preventer not required

• Frequent episodic asthma (FEA)
  • 20% of childhood asthma
  • Interval is shorter (<6-8 weeks) and only minimal symptoms in interval (i.e. exercise-induced)
  • May benefit from low-dose preventer (<=400mcg per day fluticasone) or montelukast
  • Often only troubled in winter months

• Persistent asthma (PA)
  • 5-10% of childhood asthma
  • Symptoms on most days in interval period between exacerbations
  • Commonly cause sleep disturbance, early morning chest tightness, exercise intolerance and spontaneous wheeze

History

• This episode
• Treatments used so far (relievers and preventers) + steroids
• Trigger factors (Virus, cold, exercise, passive smoking, fur)
• Frequency and course of previous episodes
• ICU admissions
• Interval symptoms

Risk factors

• Previous ICU admissions
• Poor compliance with therapy
• Significant interval symptoms
• Previous admissions in last year
• Heavy beta-agonist use
• Repeat attendances to ED
• Poorly perceived symptoms

Examination

• Wheeze intensity, pulsus paradoxus and peak expiratory flow rate are not reliable in acute exacerbations
• Asymmetry can be mucous plugging but consider FB
• Most important indicators of severity are work of breathing, mental status, ability to talk and heart rate

Assessment

Treatment

Drug dosing

• Salbutamol (100mcg/puff)
  • 6 puffs if <6yo, 12 puffs if >6yo
  • Continuous 2x5mg nebules/2.5mL if over 6 or 2×2.5mg if under 6yo
• Ipratropium (20mcg/puff)
  • 4 puffs if <6yo, 8 puffs if >6yo
  • Nebulised 250mcg q20min for 1 hour only if critical (500mcg if over 6yo)
• Prednisolone
  • 2mg/kg PO then 1mg/kg daily if ongoing need for regular salbutamol for 1-2 days
• Methylprednisolone
  • 1mg/kg IV q6h

Aminophylline

• Loading dose 10mg/kg IV (max 500mg) over 60 minutes
• Unless markedly improved, continue infusion (ICU) or q6h dosing (ward)
  • 1.1mg/kg/hr (1-9yo) or 0.7mg/kg/hr (>10yo)
• Precautions:

MgSO4

• 50% (500mg/mL)
• Dilute to 200mg/mL (by adding 1.5mL of NaCl 0.9% to each 1mL of MgSO4 for IV
• 50mg/kg over 20 minutes
• Can continue 30mg/kg/hour infusion if going to ICU targeting 1.5-2.5mmol/L level
• Precautions:

IV salbutamol

• Limited evidence for benefit
• Loading dose: 5mcg/kg/min for one hour, followed by 1-2mcg/kg/min

Salbutamol toxicity

• IV salbutamol primarily  but can occur with inhaled
• Risk of tachycardia, tachypnoea, metabolic acidosis
• Lactate commonly elevated
• Consider reducing dose or stopping salbutamol if this occurs

Investigations and Disposition

• CXR/ABG/Spirometry not usually required
• Refer if moderate/severe, poor response to inhaled salbutamol or O2 requirement
• Consider transfer if severe or critical, escalating O2 requirement, poor response or deterioration despite therapy

Discharge criteria

• Re-assess 1 hour after initial therapy
  • If clinically well, discharge
  • Suitable if subjectively considered stable on 3-4 hourly salbutamol dosing
• O2 <92% should not preclude discharge if clinically well and responded well to treatment
• Adequate oral intake
• Adequate parental education and use of spacer

Discharge requirements

• Asthma action plan
• Observe spacer use
  • Small volume recommended for all children with mask if cannot purse lips effectively
• See GP if not significantly improved at 48 hours
• Return if any deterioration despite therapy
• Review long-term asthma control
  • Consider preventer if more than one disturbed night per week, difficulty participating in physical activity, bronchodilator use more than one day per week
  • *Limited role in viral-induced wheeze/asthma
  • First-line therapy: Fluticasone or montelukast (NOT SERETIDE)
  • If commencing, arrange early Paediatric review

Primary prophylaxis

• Breastfeeding reduces likelihood of developing asthma, particularly if FHx of atopy
• Avoid antenatal and post-natal exposure to tobacco smoke
  • Increases risk of infant wheeze

Secondary prophylaxis

• House dust mite removal may reduce morbidity from asthma
  • Removal of carpets and soft toys
  • Dehumidification
  • Avoidance of bed covers
  • High temperature bed linen washing
  • Use of acaricides on soft furnishings
• Avoid exposure to tobacco smoke

Last Updated on November 9, 2021 by Andrew Crofton