02. Asthma Exacerbations

Definition

Increase in symptoms (breathlessness, wheezing, cough, chest tightness), decrease in pulmonary function as measured by a peak expiratory flow (PEF) meter (≥20% decline from patient’s baseline), and/or increased use of bronchodilators.

Evaluation

  • Precipitants: irritants (pollen, dust, smoke, detergents), infection (more than 80% of infectious triggers are viral), gastroesophageal reflux disease, medications (b-blockers, aspirin).
  • History: frequency of use of short-acting bronchodilators (e.g., albuterol, ipratropium), prior hospitalization for exacerbations, history of intubations, use of systemic glucocorticoids, exposure to known precipitants, recent trends in home PEF measurements, sick contacts, symptoms of URI.
  • Physical exam: respiratory rate, heart rate, wheezing, accessory muscle use, ability to speak in complete sentences. Altered mental status and decreased breath sounds are ominous signs.
  • Studies:
    • PEF: PEF <50% = severe exacerbation (normal PEF 450-650 L/min in men and 350-500 L/min in women). Follow serial PEFs throughout hospitalization to assess response to therapy.
    • Pulse oximetry: goal SaO2 >92% (unless underlying heart disease). Hypoxemia suggests severe exacerbation.
    • ABG: essential in severe attacks. Elevated or normal pCO2 often indication for intubation.
    • CXR: strongly consider if sign/symptoms of infection or no clear environmental precipitant.
    • Nasal swab for respiratory viral diagnostic testing, if indicated.

Management

  • Albuterol: 2.5 mg q 20 min x 3 doses by nebulization. Based on clinical response, continue q 1-4 h or continuously. MDIs plus spacer shown to be as effective as nebulizers. Use nebulizers in respiratory distress for ease of delivery. Start MDIs when patient has improved. Consider levalbuterol 1.25 mg if the patient develops severe tachycardia from albuterol.
  • Ipratropium bromide: 0.5 mg q 20 minutes x 3 doses by nebulization. Consider early or if poor response to albuterol. Early use of anticholinergics in addition to albuterol decreases hospital admission rates.
  • Steroids: prednisone 40-60 mg PO q day or IV equivalent dosing. IV not superior to PO. If unable to take PO, use methylprednisolone 60-80 mg q 6-12 h for ICU patients and 40-60 mg q 12-24 h for non-ICU patients, though dosing remains controversial. Taper over 8-10 days once PEF >50% of baseline. Start steroids early as peak effect is seen after 6 hours. Recommended duration is typically 10-14 days or shorter based on resolution of symptoms.
  • Leukotriene receptor antagonists: may be beneficial in acute asthma as add-on therapy or if exacerbation was triggered by ASA or NSAID use.
  • Heliox (mixture of O2 and He): decreases turbulent flow through spastic airways. Evidence is still evolving – a recent Cochrane review found a benefit only in patients with severe exacerbations.
  • Magnesium sulfate: consider giving magnesium sulfate 2 g IV x 1 in patients with severe asthma (PEF <40% of baseline).
  • Theophylline: avoid use. No benefit in acute attacks and potential for harm from side effects.
  • Empiric antibiotics: no added benefit unless bacterial pneumonia or sinusitis is suspected.
  • Non-invasive positive pressure ventilation: caution in acute asthma exacerbation since it could potentially delay intubation.
  • Mechanical ventilation: if patient is intubated, adopt a strategy that reduces pulmonary hyperinflation and allows adequate expiratory time.
    • Decrease minute ventilation (e.g., decreased respiratory rate and/or tidal volume) as tolerated.
    • Decrease inspiratory time (achieved by increasing flow rate). 
      • If patient is mechanically ventilated and still not improving, consider aggressive sedation to facilitate synchronization with ventilator. Avoid neuromuscular blockade, if possible, to prevent post-paralytic myopathy, as risk is increased with concomitant steroid use.

Discharge Planning

  • Use hospitalization to educate patient on proper use of inhalers, PEF monitoring, trigger avoidance, preventative care, influenza and pneumococcal vaccines, etc.
  • Patients who frequently use their beta-agonists at home but do not use steroid inhalers have a higher risk of hospitalization and ICU stay than those who use steroid inhalers. Make sure your patient is prescribed a steroid inhaler upon discharge and knows how to use it.
  • Develop an asthma action plan with the patient to avoid hospitalization with future exacerbations.

 

Currie GP, Devereux GS, Lee DK, et al. Recent developments in asthma management. BMJ 2005;330:585-589.

Manser R, Reid D, Abramson M. Corticosteroids for acute severe asthma in hospitalized patients. Cochrane Database Syst Rev 2001;(1):CD001740.

Sin DD, Man J, Sharpe H, et al. Pharmacological management to reduce exacerbations in adults with asthma: a systematic review and meta-analysis. JAMA 2004;292:367-376.

Lazarus SC. Emergency Treatment of Asthma. NEJM 2010;363:755-764

Graham V, Lasserson T, Rowe BH. Antibiotics for acute asthma. Cochrane Database Syst Rev 2001;(3):CD002741.