Asthma

DefinitionAsthma 1

Reversible obstructive lung disease

 

Clinical features:

  • SOB, wheezing, cough -> sx worse at night
  • Increased length of expiratory phase
  • Increased use of accessory resp muscles
  • Associated w\: nasal polyps + sensitivity to aspirin, eczema\atopic dermatitis

 

Diagnosis:

  • Best initial in acute exacerbations: PEF or ABG (↑ A-a gradient, resp alkalosis, hypocarbia)
  • If ABG shows resp acidosis and hypercabnia -> ICU admission
  • CXR: normal \ hyperinflation. Used to exclude other causes
  • Labs: ↑ eosinophils, IgE levels, positive skin testAsthma 2s

PFT: (most accurate)

  • ↓ FEV1, FVC, FEV1\FVC ratio
  • 12% and 200 mL ↑ of FEV1 w\ albuterol
  • If pt asx -> 20% ↓ in FEV1 w\ methacholine or histamine (not albuterol)
  • ↑ DLCO

 

Treatment:

a. Relievers: Short-acting beta blockers: Albuterol

b. Controllers: anti-inflammatory effects:

  1. Inhaled steroids (ICS): most effective
  • Beclomethasone, budesonide, fluticasone
  • Side effects: 
    • Local: dysphonia and oral candidiasis (prevented by washing the mouth after)
    • Systemic: osteoporosis, cataracts, adrenal suppression, hyperlipidemia, hyperglycemia, acne, hirsutism, thinned skin, striae, easy bruising

 

  1. Leukotruen modifiers (LTRA): for mild asthma (esp rhinitis\atopic pts)
  • Zileuton, Zafirlukast, Montelukast
  • SE (Zafirlukast): hepatotoxic, Chrug-Strauss syndrome

 

  1. Long-acting beta agonist (LABA): for nighttime and exercise induced asthma, never mono-therapy
  • Salmeterol, Formoterol
  • SE: tremors, tachycardia

 

  1. Long-acting anti-cholinergics: mainly for COPD
  • Ipratropium, tiotropium
  • SE: dry mouth, sedation

 

  1. Theophylline: (inhibits phosphodiesterase -> cAMP -> bronchodilation)
  • Narrow therapeutic index
  • Theophylline toxicity: seizures, hypotension, arrhythmias
  • Treat toxicity w\ beta blockers

Interactions:

  • ↑ theophylline levels: Cimetidine and erythromycin
  • ↓ theophylline levels: Phenytoin

 

  1. Anti-IgE: Omalizumab: for uncontrolled severe allergic asthma
  • SE: pain\bruising (subQ) and anaphylaxis

 

  1. Anti-IL5: Mepolizumab: for refractory eosinophilic asthma

 

Asthma 3.jpg

For acute exacerbations:

  • Give Oxygen + SABA 3 times every 20 min + bolus of steroids (needs 4-6 hrs to work)
  • -> inhaled ipratropium
  • -> IV magnesium sulfate (2 g infusion over 20 mins)
  • -> systemic corticosteroids (prednisone 60-120 mg PO or IV, repeat every 6 hrs as needed)

Asthma 4

 


Download the PDF version: here


References:

  • Pocket medicine
  • Step up to medicine
  • Toronto notes
  • The Johns Hopkins Internal Medicine Board Review

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