Definition of Status Asthmaticus
Status asthmaticus is defined as an acute, severe asthma exacerbation that does not respond readily to initial intensive therapy, representing a medical emergency that can lead to respiratory failure and death if not properly managed. 1
Clinical Features and Diagnostic Criteria
Status asthmaticus is characterized by:
Life-Threatening Features
- PEF <33% of predicted normal or best
- Silent chest, cyanosis, or feeble respiratory effort
- Bradycardia or hypotension
- Exhaustion, confusion, or coma 2
Arterial Blood Gas Findings
- Normal (5-6 kPa) or high arterial carbon dioxide tension (PaCO₂) in a breathless asthmatic
- Severe hypoxia: arterial oxygen tension (PaO₂) <8 kPa despite oxygen therapy
- Low pH value (acidosis) 2
Other Severe Features
- Inability to complete sentences in one breath
- Respiratory rate >25 breaths/min
- Heart rate >110 beats/min
- PEF <50% of predicted normal or best 2
Pathophysiology
The key pathophysiological consequences of status asthmaticus include:
- Severe airflow obstruction leading to dynamic hyperinflation
- Inflammatory cell infiltration and activation in airways
- Airway edema, bronchoconstriction, and mucus plugging
- Increased work of breathing leading to respiratory muscle fatigue
- Ventilation-perfusion mismatch causing hypoxemia 3
Differential Diagnosis
Status asthmaticus must be differentiated from:
- COPD exacerbation
- Vocal cord dysfunction
- Pulmonary embolism
- Congestive heart failure
- Mechanical airway obstruction (tumors, foreign bodies)
- Anaphylaxis 2
Management Approach
Immediate Management
- High-dose inhaled β-agonists: Salbutamol 5 mg or terbutaline 10 mg nebulized with oxygen
- Systemic corticosteroids: Prednisolone 30-60 mg or IV hydrocortisone 200 mg immediately
- Supplemental oxygen to maintain oxygen saturation 2
For Life-Threatening Features
- Add nebulized ipratropium (0.5 mg) to the β-agonist
- Consider IV aminophylline (250 mg over 20 minutes) or IV salbutamol/terbutaline (250 μg over 10 minutes) 2
Criteria for Hospital Admission
- Any life-threatening features
- Persistent severe features after initial treatment
- PEF <33% of predicted after nebulization
- History of previous severe attacks, especially with rapid onset 2
Mechanical Ventilation Considerations
If respiratory failure develops:
- Avoid excessive lung inflation by limiting minute ventilation
- Prolong expiratory time to prevent dynamic hyperinflation
- Accept permissive hypercapnia to prevent barotrauma
- Use sedation (propofol or benzodiazepines) to improve patient-ventilator synchrony 4
Complications and Prognosis
- In-hospital mortality for all asthmatics is 1-5%
- For critically ill asthmatics requiring intubation, mortality increases to 10-25%
- Complications include barotrauma, ventilator-associated pneumonia, and anoxic brain injury
- Patients who have suffered respiratory failure due to asthma have a 14% mortality rate at 3 years 1, 5
Prevention of Recurrence
Patients who have experienced status asthmaticus require:
- Close medical follow-up
- Optimization of maintenance therapy
- Written asthma action plan
- Education about early recognition of worsening symptoms
- Consideration for referral to an asthma specialist 2
Status asthmaticus remains a life-threatening emergency requiring prompt recognition and aggressive management to prevent respiratory failure and death.