What is the definition and treatment of asthma exacerbation?

Definition and Treatment of Asthma Exacerbation

An asthma exacerbation is defined as an acute or subacute episode of progressive worsening of symptoms and lung function compared with the patient's normal status that requires a change in treatment. 1

Definition of Asthma Exacerbation

Asthma exacerbations are characterized by:

• Progressive increase in asthma symptoms (cough, wheezing, chest tightness, dyspnoea)
• Decreased lung function (PEF or FEV1)
• Increased need for rescue medications or hospitalization 1
• Change from patient's previous status that is outside their usual range of day-to-day asthma variation 1

Classification of Exacerbations

Exacerbations are classified based on severity:

1. Severe Exacerbations:

   • Events requiring urgent action to prevent serious outcomes like hospitalization or death
   • Defined by at least one of:
     • Use of systemic corticosteroids for ≥3 days
     • Hospitalization or ER visit requiring systemic corticosteroids 1
   • Clinical indicators: marked respiratory distress, inability to speak in full sentences, respiratory rate >30/min, oxygen saturation <90%, PaCO2 >42 mmHg (indicating impending respiratory failure) 2

2. Moderate Exacerbations:

   • Events troublesome to the patient requiring temporary treatment change
   • Features include deterioration in symptoms, lung function, and increased rescue bronchodilator use lasting ≥2 days
   • Not severe enough to warrant systemic corticosteroids or hospitalization
   • May include ER visits not requiring systemic corticosteroids 1

3. Mild Exacerbations:

   • The American Thoracic Society/European Respiratory Society statement does not recommend defining mild exacerbations as they cannot be reliably distinguished from transient loss of asthma control 1

Assessment of Exacerbation Severity

Assessment should include:

• Vital signs: Pulse rate, respiratory rate, oxygen saturation
• Physical examination: Degree of breathlessness, use of accessory muscles, wheezing, level of consciousness
• Lung function: PEF or FEV1 measurement when possible
• Laboratory tests: Pulse oximetry (hypoxemia defined as SpO2 <90-92%) 1
• Arterial blood gases: Particularly important in severe exacerbations to monitor for respiratory failure 2

Warning Signs of Life-Threatening Exacerbation

• Transition from respiratory alkalosis to normal PaCO2 in severe asthma (indicates respiratory muscle fatigue)
• Development of hypercapnia (PaCO2 >42 mmHg) signaling respiratory failure
• Altered mental status, exhaustion, silent chest 2

Treatment of Asthma Exacerbation

Home Management

For patients ≥12 years:

• Inhaled corticosteroid/formoterol combination for those not on maintenance ICS/LABA
• Short-acting beta2 agonist (SABA) for those using ICS/LABA maintenance that doesn't include formoterol 3

For children 4-11 years:

• Inhaled corticosteroid/formoterol inhaler (up to 8 puffs daily) to reduce exacerbation risk 3

Office/Emergency Management

1. Initial Assessment and Treatment:

   • Oxygen therapy to maintain SpO2 ≥93-95%
   • Repeated doses of SABA (albuterol) every 20 minutes for one hour 4, 3
   • Early administration of systemic corticosteroids for moderate to severe exacerbations

2. For Severe Exacerbations:

   • Transfer to acute care facility
   • Continuous oxygen therapy
   • Frequent administration of SABA
   • Systemic corticosteroids
   • Consider adding short-acting muscarinic antagonist
   • Consider magnesium sulfate infusion (reduces hospitalization rates) 3

3. Monitoring:

   • Continuous monitoring of vital signs and oxygen saturation
   • Serial measurement of lung function (PEF or FEV1)
   • Arterial blood gases in severe cases to monitor for respiratory failure 2

Hospital Management

• Continued monitoring and systemic therapy similar to emergency department
• Discharge considerations: Improvement in symptoms and FEV1 or PEF to 60-80% of predicted values 3

Post-Exacerbation Care

• Addition or adjustment of inhaled corticosteroids
• Consider stepping up asthma maintenance therapy
• Close follow-up (within 1-2 weeks)
• Education on asthma action plans 3

Common Pitfalls in Management

• Misinterpreting acid-base status: Normal or elevated PaCO2 in severe asthma indicates decompensation, not improvement 2
• Underestimating severity: Patients may appear deceptively stable despite significant airflow obstruction
• Inadequate corticosteroid dosing or duration
• Failure to identify and address triggers or comorbidities that may have precipitated the exacerbation
• Premature discharge without adequate follow-up plan

Long-Term Implications

Severe asthma exacerbations are associated with accelerated decline in lung function over time. Treatment with inhaled corticosteroids can attenuate this decline, highlighting the importance of prevention and proper management of exacerbations 5.