How should I treat an acute asthma exacerbation, including initial therapy, discharge criteria, and next-step options?

Management of Acute Asthma Exacerbation

Immediately administer high-flow oxygen (40-60%), nebulized salbutamol 5-10 mg, and systemic corticosteroids (prednisolone 30-60 mg orally or hydrocortisone 200 mg IV) to all patients with acute severe asthma, as CO2 retention is not aggravated by oxygen therapy in asthma and delay can be fatal. 1, 2

Initial Assessment and Severity Classification

Assess severity objectively using peak expiratory flow (PEF) and clinical parameters, as physician subjective assessments are often inaccurate 3:

Acute Severe Asthma:

• PEF <50% predicted or best 1
• Respirations ≥25 breaths/min 1
• Pulse ≥110 beats/min 1
• Inability to complete sentences 1

Life-Threatening Features (requiring immediate ICU consideration):

• PEF <33% predicted 1, 2
• Silent chest, cyanosis, or feeble respiratory effort 1, 2
• Hypercapnia (PaCO2 >45 mmHg), respiratory acidosis, or severe hypoxemia 2
• Exhaustion, confusion, altered consciousness, or bradycardia 1, 2

Immediate Treatment Protocol

First-Line Therapy (administer simultaneously):

Oxygen:

• Deliver 40-60% oxygen via high-flow face mask to maintain SpO2 >92% 1, 4, 2
• Never withhold oxygen due to hypercapnia concerns—this is a critical pitfall unique to asthma (unlike COPD) 2

Bronchodilators:

• Nebulized salbutamol 5-10 mg (or terbutaline 5-10 mg) via oxygen-driven nebulizer 1, 2
• Repeat every 15-30 minutes if no improvement 1

Systemic Corticosteroids:

• Prednisolone 30-60 mg orally OR hydrocortisone 200 mg IV 1
• Administer immediately without waiting for investigations, as clinical benefits require 6-12 hours to manifest 3
• Underuse of corticosteroids is a major factor in preventable asthma deaths 5

Monitoring:

• Repeat PEF measurement 15-30 minutes after starting treatment 1, 4
• Continuous pulse oximetry maintaining SpO2 >92% 1, 4
• Obtain chest radiograph to exclude pneumothorax 1

Escalation for Non-Responders (15-30 minutes)

If patient shows no improvement after initial therapy:

• Continue oxygen and systemic steroids 1
• Increase nebulized β-agonist frequency to every 15-30 minutes 1, 4
• Add ipratropium 0.5 mg to nebulizer, repeat every 6 hours 1, 4
• Repeat blood gas within 2 hours if initial PaO2 <60 mmHg or PaCO2 was normal/elevated 1, 2

For Life-Threatening Features:

• Transfer to ICU immediately with physician prepared to intubate 2
• Consider IV aminophylline 5 mg/kg over 20 minutes, then 1 mg/kg/hour maintenance (omit loading dose if already on oral theophyllines) 4

ICU Transfer Criteria

Transfer accompanied by physician prepared to intubate if: 1, 2

• Deteriorating PEF despite treatment
• Worsening or persistent hypoxia/hypercapnia
• Exhaustion, feeble respirations, confusion, drowsiness, or coma
• Respiratory arrest

Discharge Criteria

Patients must meet ALL of the following before discharge: 1, 5

• On discharge medications for ≥24 hours 1, 5
• PEF >75% predicted or personal best with <25% diurnal variability 1, 5
• Inhaler technique checked and documented 1, 5
• Written self-management plan provided 1, 5

Discharge Medications:

• Oral prednisolone 30-60 mg daily for 3-10 days (no taper needed if <10 days) 5
• Inhaled corticosteroids at higher dose than pre-admission 5
• Bronchodilators (inhaled β-agonists) 1
• Own peak flow meter 1

Mandatory Follow-Up:

• Primary care within 1 week (ideally within 48 hours) 1, 5
• Respiratory clinic within 4 weeks 1

Critical Pitfalls to Avoid

• Never administer sedatives—they are absolutely contraindicated in acute severe asthma 2
• Never withhold oxygen due to hypercapnia concerns (this applies to COPD, not asthma) 2
• Never delay corticosteroids for investigations—administer immediately 4, 3
• Never underestimate severity based on subjective assessment—use objective PEF measurements 3
• Never discharge without written instructions—this significantly increases relapse risk 5
• Never rely solely on inhaler therapy in acute severe asthma—failure to respond is a red flag requiring escalation 4

Pediatric Considerations

Acute Severe Asthma Recognition in Children: 1, 4

• Too breathless to talk or feed
• Respirations >50 breaths/min
• Pulse >140 beats/min
• PEF <50% predicted

Immediate Treatment: 1, 4

• High-flow oxygen via face mask (maintain SpO2 >92%)
• Nebulized salbutamol 2.5-5 mg (half dose in very young children)
• IV hydrocortisone immediately
• Add ipratropium 100 mcg nebulized every 6 hours

Discharge Steroid Regimen: 5

• Prednisolone 1-2 mg/kg/day (maximum 60 mg/day) for 3-10 days
• No taper needed if course <10 days
• Initiate inhaled corticosteroids at higher dose than pre-admission