What is the recommended assessment and immediate treatment for an acute asthma exacerbation, including oxygen saturation goals, bronchodilator regimen, systemic corticosteroid dosing, and indications for hospital admission?

Acute Asthma Exacerbation Management

For acute asthma exacerbations, immediately administer high-dose inhaled beta-agonists (salbutamol 5 mg or terbutaline 10 mg via nebulizer), systemic corticosteroids (prednisolone 30-60 mg orally or hydrocortisone 200 mg IV), and supplemental oxygen to maintain SpO2 >92%, with hospital admission indicated for life-threatening features or persistent severe symptoms after initial treatment. 1

Severity Assessment

Objective measurements are critical—severity is frequently underestimated when relying on clinical impression alone 1.

Features of Severe Asthma

• Too breathless to complete sentences in one breath 1
• Respiratory rate >25 breaths/min 1
• Heart rate >110 beats/min 1
• Peak expiratory flow (PEF) <50% of predicted or personal best 1

Life-Threatening Features

• PEF <33% of predicted or personal best 1
• Silent chest, cyanosis, or feeble respiratory effort 1
• Bradycardia or hypotension 1
• Exhaustion, confusion, or coma 1
• Normal (5-6 kPa) or elevated PaCO2 in a breathless patient 1, 2
• Severe hypoxia: PaO2 <8 kPa (60 mmHg) despite oxygen therapy 1

Immediate Treatment Protocol

Begin all three components simultaneously—do not delay 1.

Oxygen Therapy

• Administer 40-60% oxygen via face mask or nasal cannula 1, 2
• Target SpO2 >92% (>95% in pregnant women and patients with heart disease) 1
• CO2 retention is not aggravated by oxygen therapy in asthma 1
• Maintain continuous pulse oximetry until clear response occurs 1

Inhaled Beta-Agonists

• Initial dose: Salbutamol 5 mg or terbutaline 10 mg via oxygen-driven nebulizer 1
• Alternative delivery: 10-20 puffs (2 puffs repeated 10-20 times) via metered-dose inhaler with large spacer device 1
• Frequency: Repeat every 20-30 minutes for first hour (3 treatments total) 1
• For severe exacerbations (PEF <40%), continuous nebulization may be more effective than intermittent dosing 1
• After initial hour, adjust frequency based on response—typically every 1-4 hours 1

Systemic Corticosteroids

• Oral route (preferred): Prednisolone 30-60 mg daily 1, 3
• IV route (if vomiting or severely ill): Hydrocortisone 200 mg immediately, then 200 mg every 6 hours 1, 3
• Oral administration is equally effective as IV when GI absorption is intact 1, 3
• Administer within 1 hour of presentation—anti-inflammatory effects take 6-12 hours to manifest 3
• Continue until PEF reaches 70% of predicted or personal best, typically 5-10 days 3
• No tapering required for courses <7-10 days, especially if on inhaled corticosteroids 3

Additional Therapy for Life-Threatening Features

If any life-threatening features are present, immediately add 1:

• Ipratropium bromide: 0.5 mg nebulized with beta-agonist, repeat every 6 hours 1
• IV aminophylline: 250 mg over 20 minutes OR salbutamol/terbutaline 250 µg over 10 minutes 1
• Critical warning: Do not give bolus aminophylline to patients already taking oral theophyllines 1

Monitoring Requirements

Initial Assessment (15-30 minutes after treatment)

• Repeat PEF measurement 1
• Continuous pulse oximetry maintaining SpO2 >92% 1
• Reassess respiratory rate, heart rate, ability to speak 1

For Patients Admitted to Hospital

• Arterial blood gases should always be measured 1
• Chest radiography to exclude pneumothorax, consolidation, or pulmonary edema 1
• Plasma electrolytes, urea, blood count 1
• ECG in patients >50 years or with known heart disease 1

Repeat blood gases within 2 hours if 1:

• Initial PaO2 <8 kPa (60 mmHg)
• Initial PaCO2 was normal or elevated
• Patient deteriorates despite treatment
• SpO2 cannot be maintained >92%

Hospital Admission Criteria

Immediate hospital referral is required for 1:

• Any life-threatening features present
• Features of severe attack persisting after initial treatment
• PEF 15-30 minutes after nebulization <33% of predicted or best

Lower threshold for admission in patients 1:

• Presenting in afternoon/evening rather than morning
• Recent nocturnal symptoms or symptom worsening
• Previous severe attacks, especially with rapid onset
• Concern over patient's assessment of severity
• Inadequate social circumstances or support

ICU Transfer Criteria

Transfer to intensive care unit with physician prepared to intubate if 1, 2:

• Deteriorating PEF despite maximal therapy
• Worsening or persisting hypoxia (PaO2 <8 kPa)
• Rising PaCO2 or respiratory acidosis 2
• Exhaustion, confusion, or drowsiness
• Respiratory arrest

Discharge Criteria

Patients should not be discharged until 1:

• On discharge medication for 24 hours with documented proper inhaler technique
• PEF >75% of predicted with variability <25%
• Receiving oral and inhaled steroids plus bronchodilators
• Written self-management plan provided
• GP follow-up arranged within 1 week
• Respiratory clinic appointment within 4 weeks

Pediatric Considerations

Recognition of Severe Asthma in Children

• Too breathless to talk or feed 1
• Respiratory rate >50 breaths/min 1
• Heart rate >140 beats/min 1
• PEF <50% predicted 1

Pediatric Dosing

• Salbutamol: 2.5 mg (age ≤2 years) or 5 mg (age >2 years) via nebulizer 4
• Alternative: 4-8 puffs via MDI with spacer every 20 minutes 4
• Prednisolone: 1-2 mg/kg/day in 2 divided doses (maximum 60 mg/day) 3, 4
• IV hydrocortisone: 200 mg every 6 hours if unable to take oral 4
• Ipratropium: 100 mcg nebulized every 6 hours 4

MDI with large volume spacer is equally effective to nebulization in children and may result in lower admission rates with fewer cardiovascular side effects 4.

Critical Pitfalls to Avoid

• Never delay systemic corticosteroids—underuse is a documented cause of preventable asthma deaths 3, 4
• Do not underdose corticosteroids—single 100 mg hydrocortisone doses are insufficient and potentially fatal 2
• Avoid sedatives of any kind—they can depress respiratory function 4
• Do not rely on clinical impression alone—always obtain objective measurements (PEF, SpO2) 1
• Recognize that normal PaCO2 in a breathless asthmatic indicates impending respiratory failure, not improvement 1, 2
• Do not use antibiotics routinely—only if bacterial infection is confirmed 4