What is the initial treatment for a patient with severe dyspnea and hypoxemia on oxygen with a history of asthma in the emergency department?

Emergency Management of Severe Asthma with Hypoxemia

Immediately administer high-flow oxygen (40-60% via reservoir mask at 15 L/min if SpO2 <85%, otherwise nasal cannulae at 2-6 L/min), nebulized salbutamol 5 mg (or terbutaline 10 mg) via oxygen-driven nebulizer, and systemic corticosteroids (prednisolone 30-60 mg orally or hydrocortisone 200 mg IV) within the first few minutes of arrival. 1, 2

Immediate Assessment and Recognition

Severity Markers

• Severe asthma features include inability to complete sentences in one breath, respiratory rate >25 breaths/min, heart rate >110 beats/min, and peak expiratory flow (PEF) <50% predicted or personal best 1, 2
• Life-threatening features requiring immediate ICU consideration include PEF <33% predicted, silent chest, cyanosis, feeble respiratory effort, bradycardia, hypotension, exhaustion, confusion, or coma 1, 2
• Measure arterial blood gases if any severe features are present—normal or elevated PaCO2 (≥42 mmHg) in a breathless asthmatic patient indicates impending respiratory failure 1, 3

Critical Pitfall

The severity of asthma attacks is frequently underestimated by patients, families, and clinicians due to failure to make objective measurements—never rely on subjective assessment alone 1, 2

First-Line Treatment (Start Simultaneously)

Oxygen Therapy

• Target SpO2 94-98% for patients without COPD risk factors 1, 2
• If initial SpO2 <85%, use reservoir mask at 15 L/min immediately 1, 2
• If SpO2 ≥85%, use nasal cannulae at 2-6 L/min or simple face mask at 5-10 L/min 1, 2
• CO2 retention is NOT aggravated by oxygen therapy in asthma—never withhold oxygen due to hypercapnia concerns 1, 3

Nebulized Beta-Agonist

• Administer salbutamol 5 mg or terbutaline 10 mg via oxygen-driven nebulizer immediately 1, 2, 4
• Repeat every 20 minutes for 3 doses, then reassess 1, 2
• If no nebulizer available, give 10-20 puffs (2 puffs repeated) via metered-dose inhaler with large volume spacer 1

Systemic Corticosteroids

• Give prednisolone 30-60 mg orally OR hydrocortisone 200 mg IV (or both if very ill) immediately—do not delay 1, 2
• Corticosteroids take 6-12 hours to show effect, making early administration critical 1, 2

Additional Treatment for Life-Threatening Features

If any life-threatening features are present:

• Add ipratropium bromide 0.5 mg to the nebulized beta-agonist 1, 2, 5
• Consider IV aminophylline 250 mg over 20 minutes OR salbutamol/terbutaline 250 µg IV over 10 minutes 1
• Critical warning: Do NOT give bolus aminophylline to patients already taking oral theophyllines 1
• Consider IV magnesium sulfate 2 g over 20 minutes for severe refractory cases 1, 2

Monitoring and Reassessment (15-30 Minutes After Initial Treatment)

• Measure PEF or FEV1 before and after each treatment 2
• Monitor oxygen saturation continuously 2
• Repeat arterial blood gases within 2 hours if initial PaO2 <8 kPa or if PaCO2 was normal/elevated 1, 3

If Patient is Improving:

• Continue oxygen 40-60% 1
• Continue prednisolone 30-60 mg daily or IV hydrocortisone 200 mg every 6 hours 1
• Continue nebulized beta-agonist every 4-6 hours 1

If Patient is NOT Improving After 15-30 Minutes:

• Increase nebulized beta-agonist frequency to every 15-30 minutes 1
• Add ipratropium 0.5 mg to nebulizer if not already given, repeat every 6 hours 1
• Consider continuous nebulization of albuterol 1, 2
• Obtain chest X-ray to exclude pneumothorax, consolidation, or pulmonary edema 1

Absolute Contraindications

• Never administer sedatives of any kind to patients with acute asthma 1, 2, 3
• Avoid aggressive hydration in older children and adults 2
• Do not use methylxanthines as first-line therapy due to increased side effects without superior efficacy 2

Criteria for ICU Transfer

Transfer immediately if patient has: 1, 3

• Deteriorating PEF despite treatment
• Worsening or persisting hypoxia
• Hypercapnia (PaCO2 >6 kPa/45 mmHg)
• Exhaustion, confusion, drowsiness, or altered mental status
• Silent chest with feeble respiratory effort
• Bradycardia or cardiovascular instability

Hospital Admission Criteria

Admit if: 1, 2

• Any life-threatening features present
• Features of severe attack persist after initial treatment
• PEF remains <33% predicted after treatment
• PEF <50% predicted after 1-2 hours of intensive treatment
• Lower threshold for admission if patient presents in afternoon/evening, has recent nocturnal symptoms, previous severe attacks, or concerning social circumstances 1, 2