TOC | Pulm

Asthma        See also See also   Bronchitis/ COPD  |  Status Asthmatica  

Gerald W. Staton, Jr., M.D., and Roland H. Ingram, Jr., M.D.  -  Emory University School of Medicine

Definition/Key Clinical Features
Differential Diagnosis
Best Tests
Best Therapy
Best References

Definition/Key Clinical Features

• Reversible narrowing of airways in response to various stimuli and airway inflammation
• During periods of normal lung function, no abnormal physical findings
• Symptoms: always try to quantify—e.g., mild-moderate-severe, scale 1–5
  • Wheezing
  • Cough (nonproductive or with copious sputum)
  • Shortness of breath
  • Chest tightness (often confused with angina pectoris)
  • Desperate hunger for air with severe attacks

Differential Diagnosis

• Upper airway obstruction
• Viral tracheobronchitis
• Chronic obstructive pulmonary disease
• Congestive heart failure
• Pulmonary embolism
• Churg-Strauss syndrome

Best Tests

No single lab test can establish diagnosis; bronchodilator responsiveness provides supportive evidence

• Spirometry
  • > 15% increase in airflow (FEV₁ or FVC) after bronchodilator inhalation suggests asthma
  • Lacks sensitivity and specificity
  • False negatives occur during asymptomatic periods
  • False positives occur with chronic bronchitis, emphysema, or other diseases with chronic airflow obstruction
• Bronchoprovocation with methacholine
  • May be helpful if pulmonary function is normal
  • Abnormal response is > 20% decline in FEV₁
  • Other provocative agents are cold, exercise, and histamines
• CXR may exclude alternative diagnoses; not recommended for screening or diagnosis
• CBC, sputum exam, IgE measurement, allergy skin test not useful in most cases

Red Flags

• Following factors suggest greater risk:
  • Advanced age
  • Greater airway reactivity
  • Previous use of mechanical ventilation
  • Long-term steroid therapy
  • Previous hospitalizations for asthma
  • Problems with compliance
  • Major psychiatric diagnoses
  • Use of major tranquilizers

Best Therapy

Emergency

• Assess oxygenation by pulse oximetry
• Increase O₂ sat to >90%
• Measure ABGs
• Rapidly evaluate for hypercapnia, pneumothorax, atelectasis, or pneumonia
• Administer shorter-acting beta-adrenergic agonist by inhalation

Agents for Persistent Asthma            

Bronchodilators for Asthma

• Inhaled short-acting beta₂ agonists: first-line p.r.n. therapy; no significant differences in efficacy among inhaled short-acting beta₂ agonists; dilute aerosols to minimum of 4 ml at gas flow of 6-8 L/min
  • Albuterol
    • Nebulizer, 5 mg/ml
      • Dose: maintenance, 1.25–5.0 mg q. 4–8 hr p.r.n; exacerbation, 5 mg q. 2 hr
      • Cost/mo: $30.00–39.99
    • MDI, 84 ¼g/puff: MDI as effective as nebulizer when used with spacer
      • Dose: maintenance, 2–4 puffs q. 6 hr p.r.n; exacerbation, 3–8 puffs q. 2 hr
    • DPI, 200 ¼g/capsule
      • Dose: maintenance, 1–2 capsules q. 6 hr p.r.n; exacerbation, not studied
  • Bitolterol
    • Nebulizer, 2 mg/ml
      • Dose: maintenance, 0.5–3.5 q. 4–8 hr p.r.n.; exacerbation, not studied
      • Cost/mo: price not available.
    • MDI, 370 ¼g/puff
      • Dose: maintenance, 2–4 puffs q. 6 hr p.r.n.; exacerbation, not studied
      • Cost/mo: price not available.
  • Pirbuterol
    • MDI, 200 ¼g/puff
      • Dose: maintenance, 2–4 puffs q. 6 hr p.r.n.; exacerbation, not studied
      • Cost/mo: $20.00–29.99 per inhalation
• Inhaled long-acting beta₂ agonists: first-line scheduled bronchodilator therapy
  • Salmeterol: Slower onset of action; not used as a rescue bronchodilator
    • MDI, 21 ¼g/puff
      • Dose: maintenance, 2 puffs q. 12 hr; exacerbation, not recommended
      • Cost/mo: $50.00–69.99
    • DPI, 50 ¼g/blister
      • Dose: maintenance, 1 blister q. 12 hr
  • Formoterol: faster onset of action than salmeterol; may be used as a rescue bronchodilator
    • DPI, 12 ¼g/capsule
      • Dose: maintenance, 1 capsule q. 12 hr; exacerbation, not recommended
      • Cost/mo:
• Inhaled anticholinergics: indicated in combination with inhaled short-acting beta₂ agonists for exacerbations
  • Ipratropium bromide:
    • Nebulizer, 0.25 mg/ml: may mix with albuterol in same nebulizer
      • Dose: maintenance, not recommended; exacerbation, 0.5 mg q. 2–8 hr
      • Cost/mo: $30.00-34.99
    • MDI, 18 ¼g/puff: as effective as nebulizer when used with spacer
      • Dose: maintenance, not recommended; exacerbation, 3-8 puffs q. 3–4 hr
      • Cost/mo: $30.00–34.99
• Combined short-acting beta₂ agonist and anticholinergic: use when both are indicated
  • MDI albuterol (90 ¼g/puff) + ipratropium bromide (18 ¼g/puff)
    • • Dose: maintenance, not recommended; exacerbation, 3–8 puffs q. 2 hr
      • Cost/mo: $30.00–39.99
• Theophylline: third choice; relatively weak bronchodilator; used only when all other agents optimized; significant toxicity; must monitor levels
  • Dose: maintenance, 100–200 mg b.i.d.; exacerbation, adjust to serum level 10–20 µg/ml
  • Cost/mo: $10.00–19.99

  [DPI—dry-powder inhaler; MDI--metered-dose inhaler]

Anti-inflammatory Agents for Asthma            

Systemic Corticosteroids

• Prednisone: usual oral agent; q.d. initially, then wean off, if possible, or switch to q.o.d.
  • Dose: initial, 0.5-1.0 mg/kg/day; maintenance, none or minimal
  • Cost/mo: $5.00
• Methylprednisolone, oral: less commonly used oral agent; q.d. initially, then wean off, if possible, or switch to q.o.d.
  • Dose: initial, 24-48 mg/day; maintenance, none or minimal
  • Cost/mo: $9.00-43.00
• Methylprednisolone, I.V.: usual I.V. agent; oral therapy is as effective
  • Dose: initial, 60-125 mg q. 6-8 hr; maintenance, none
  • Cost/mo: $24.00-26.99

Inhaled Corticosteroids: first choice of anti-inflammatory agents; various inhaled corticosteroid agents differ in potency

• Fluticasone: highest potency; also formulated in combination with salmeterol in DPI
  • Dose: low, 83-264 µg; medium, 264-660 µg; high, > 660 µg
    • 44 µg/puff: low, 2-4 puffs/day
    • 110 µg/puff: low, 2 puffs/day; medium, 2-6 puffs/day; high, > 6 puffs/day
    • 220 µg/puff: medium, 1-2 puffs/day; high, > 3 puffs/day
  • Cost/mo: $40.00-49.99
• Budesonide: second-highest potency; DPI inhaler
  • Dose: low, 200-400 µg; medium, 400-600 µg; high, > 600 µg
    • 220 µg/puff: low, 1-2 puffs/day; medium, 2-3 puffs/day; high, > 3 puffs/day
  • Cost/mo: $30.00-39.99
• Beclomethasone: third-highest potency; available in HFA MDI, possibly improving effectiveness
  • Dose: low, 168-504 µg; medium, 504-840 µg; high, > 840 µg
    • 42 µg/puff: low, 4-12 puffs/day; medium, 12-20 puffs/day; high, > 20 puffs/day
  • Cost/mo: $30.00-39.99
• Flunisolide: lowest potency
  • Dose: low, 500-1,000 µg; medium, 1,000-2,000 µg; high, > 2000 µg
    • 42 µg/puff: low, 4-12 puffs/day; medium, 12-20 puffs/day; high, > 20 puffs/day
  • Cost/mo: $50.00-59.00
• Triamcinolone: lowest potency; provided with spacer
  • Dose: low, 400-1,000 µg; medium, 1,000-2,000 µg; high, > 2,000 µg
    • 100 µg/puff: low, 4-10 puffs/day; medium, 10-20 puffs/day; high, > 20 puffs/day
  • Cost/mo: $50.00-59.00

Cromolyn Sodium: much less potent than inhaled steroids; used more often in children; no steroid side effects

• Dose: initial, 2 puffs q.i.d.; maintenance, 2 puffs q.i.d.
  • Cost/mo: $30.00-39.99/canister

Nedocromil: much less potent than inhaled steroids; no steroid side effects

• Dose: initial, 2 puffs q.i.d.; maintenance, 2 puffs q.i.d.
  • Cost/mo: $50.00-59.99

Other Agents for Asthma

Leukotriene Inhibitors: less effective than inhaled corticosteroids; help with associated allergic rhinitis; use for aspirin-sensitive patients

• Montelukast: first choice of leukotriene inhibitors; note q.h.s. dosing; no lab monitoring or restrictions related to meals
  • Dose: 10 mg q.h.s.
  • Cost/mo: $60.00-69.99
• Zafirlukast: should be taken at least 1 hr before or 2 hr after meals
  • Dose: 20 mg b.i.d.
  • Cost/mo: $50.00-59.00
• Zileuton: must monitor LFTs
  • Dose: 600 mg q.i.d.
  • Cost/mo: $79.00-89.99
• Methotrexate: efficacy controversial; toxic drug, must monitor blood counts and LFTs closely; should be given only by asthma expert
  • Dose: 7.5 mg/wk (adjust to effect; maximum 25 mg/wk)
  • Cost/mo: $10.00-19.99

[DPI—dry-powder inhaler; HFA—hydrofluoroalkane; MDI—metered-dose inhaler]

Best References

• Busse W, Raphael GD, Galant S, et al: Low-dose fluticasone propionate compared with montelukast for first-line treatment of persistent asthma: a randomized clinical trial. J Allergy Clin Immunol 107:461, 2001

• Busse WW, Lemanske RF Jr: Asthma. N Engl J Med 344:350, 2001

• Busse, et al: J Allergy Clin Immunol 107:461, 2001

• Busse, et al: N Engl J Med 344:350, 2001

• Cochrane, et al: Chest 117:542, 2000

• NIH Guidelines (NIH Publication No 97-4051), Bethesda, Maryland, 1997 (www.nhlbi.nih.gov/health/prof/lung/asthma/practgde.htm)

• Shrewsbury, et al: BMJ 320:1368, 2000
• Suissa, et al: J Allergy Clin Immunol 107:937, 2001
• Taylor, et al: Thorax 55:595, 2000
• Virchow, et al: Am J Respir Crit Care Med 162:578, 2000

July 2004