Acute Asthma in Children

Acute asthma in children is an acute or subacute worsening of asthma symptoms with airflow obstruction, triggered most often by viral infection, allergens, smoke or exercise.

• Asthma is the commonest chronic disease of childhood. Exacerbations are a leading cause of hospital admission.
• Risk factors for severe attacks include previous severe attacks, intensive care admission, poor control, overuse of reliever inhaler, non-adherence, smoke exposure, poverty, and food allergy.
• Death is rare but occurs, usually after delayed treatment or underestimation of severity.
• Severity is assessed by speech, work of breathing, saturation and peak flow.

Symptoms vary with severity.

• Cough (often worse at night), wheeze, shortness of breath and chest tightness.
• Mild-moderate: able to talk in sentences, saturation 92 percent or more, peak flow above 50 percent of best.
• Severe: too breathless to talk or feed, respiratory rate above 40 (ages 2 to 5 years) or above 30 (over 5 years), heart rate above 140 (2 to 5 years) or above 125 (over 5 years), use of accessory muscles, saturation below 92 percent, peak flow 33 to 50 percent.
• Life-threatening: silent chest, cyanosis, poor respiratory effort, exhaustion, confusion or drowsiness, hypotension, peak flow below 33 percent, saturation below 92 percent with normal PaCO2.
• Differential diagnosis: viral-induced wheeze, bronchiolitis, pneumonia, foreign body, anaphylaxis, vocal cord dysfunction, croup, cystic fibrosis, heart failure and pneumothorax.
• Complications: respiratory failure, pneumothorax, pneumomediastinum, atelectasis, hypokalaemia, lactic acidosis and death.

Diagnosis is clinical in known asthmatics.

• Assess severity: speech, respiratory rate, heart rate, work of breathing, saturation and peak flow (if older than 5 years and able).
• Do not delay treatment for investigation.
• Chest X-ray only if suspecting pneumothorax, pneumonia, foreign body or life-threatening disease unresponsive to therapy.
• Blood gas for severe disease.
• Check electrolytes (potassium) after repeated salbutamol.

Early oxygen, bronchodilator and steroid.

• Supportive: sit upright, oxygen to target saturation 94 to 98 percent, fluids, reassure, treat fever.
• Pharmacological, salbutamol: 2 to 10 puffs (100 micrograms each) via spacer, one puff at a time with 5 breaths each, repeated every 20 minutes for the first hour, then every 1 to 4 hours. Alternatively nebulised salbutamol 2.5 mg (under 5 years) or 5 mg (over 5 years), repeated every 20 minutes, or continuous.
• Ipratropium bromide: 250 micrograms (under 5 years) or 500 micrograms (over 5 years) nebulised every 20 minutes for 3 doses in moderate-severe asthma, or 4 to 8 puffs (20 micrograms each) by spacer.
• Corticosteroids within one hour: prednisolone 1 to 2 mg/kg orally once daily (maximum 40 mg for under 5 years, 60 mg for older) for 3 to 5 days, or dexamethasone 0.6 mg/kg once (maximum 16 mg), repeated in 24 hours. Hydrocortisone 4 mg/kg intravenously every 6 hours (maximum 100 mg) if unable to take oral.
• Severe or life-threatening, unresponsive to initial bronchodilators and steroids: intravenous magnesium sulfate 40 mg/kg (maximum 2 g) over 20 minutes, intravenous salbutamol 15 micrograms/kg over 10 minutes then infusion 1 to 5 micrograms/kg/min, intravenous aminophylline 5 mg/kg over 20 minutes then 1 mg/kg/h (omit loading dose if already on theophylline).
• Procedures: intubation and ventilation as a last resort (permissive hypercapnia strategy).
• Special groups: infants under 2 years need careful assessment, as response differs. Admit all children with severe features, persisting hypoxia, or poor response after 1 hour of treatment.
• Red flags: silent chest, cyanosis, exhaustion, altered consciousness, saturation below 92 percent, poor response to bronchodilators, and previous intensive care admission.
• Follow-up: discharge when reliever is needed no more than 4-hourly, saturation 94 percent or more. Written asthma action plan, check inhaler technique, start or step up controller (inhaled corticosteroid), and review within 48 hours to 1 week.