🚨 Acute Severe Asthma
Overview
Acute severe asthma is a medical emergency characterised by rapidly worsening asthma symptoms that are unresponsive to usual bronchodilator therapy. It can quickly progress to life-threatening asthma and respiratory arrest. Prompt recognition and aggressive treatment are essential.
Recognition
Look for inability to complete sentences in one breath, respiratory rate ≥25/min, heart rate ≥110/min, and PEFR 33-50% of best or predicted. Signs of life-threatening asthma include silent chest, cyanosis, exhaustion, altered conscious level, hypotension, or PEFR <33%.
Initial Assessment (ABCDE)
A: Assess for airway patency. B: Assess respiratory rate, SpO2, work of breathing, and listen for breath sounds. Administer high-flow oxygen. C: Assess heart rate, blood pressure, and capillary refill. D: Assess conscious level (AVPU/GCS). E: Look for signs of infection or other triggers.
Red Flags
Deterioration to life-threatening asthma (silent chest, cyanosis, exhaustion, altered conscious level, hypotension, PEFR <33%), increasing CO2 on blood gas, or cardiac arrest. These indicate imminent respiratory failure and require immediate, aggressive intervention.
Investigations
Bedside: SpO2, PEFR (if able), ECG. Bloods: Arterial blood gas (ABG) to assess oxygenation and CO2 retention, urea and electrolytes (monitor for hypokalaemia from nebulisers). Imaging: Chest X-ray (if suspected pneumothorax, pneumonia, or not responding to treatment).
Immediate Management
Administer high-flow oxygen to maintain SpO2 94-98%. Give high-dose inhaled short-acting beta-2 agonists (e.g., salbutamol) via oxygen-driven nebuliser. Administer systemic corticosteroids (e.g., prednisolone orally or hydrocortisone intravenously). Consider inhaled ipratropium bromide. If severe, consider intravenous magnesium sulphate. Monitor closely.
Escalation Triggers
Any patient with acute severe asthma requires senior medical review. Failure to improve with initial therapy, deterioration to life-threatening asthma, persistent hypoxaemia, rising CO2, or signs of exhaustion mandates urgent critical care involvement and consideration for non-invasive or invasive ventilation.
MLA High-Yield Notes
The key treatments are oxygen, nebulised beta-2 agonists, and systemic corticosteroids. A 'silent chest' is a critical sign of life-threatening asthma, indicating very poor air entry. A normal or rising pCO2 in severe asthma is a worrying sign of impending respiratory failure. Always check for triggers like infection or medication non-compliance.
References
- British Thoracic Society (BTS)/Scottish Intercollegiate Guidelines Network (SIGN) Asthma Guideline
- Resuscitation Council UK: Adult Advanced Life Support Guidelines
- NICE Guideline NG80: Asthma: diagnosis, monitoring and routine management