Updated: 3/28/2022

Asthma

0%
Topic
Review Topic
0
0
N/A
N/A
Questions
14
0
0
100%
0%
Evidence
17
0
0
100%
0%
Videos / Pods
2
Topic
Snapshot
  • A five-year-old with severe asthma is being treated in the ER with a IV aminophylline drip. The child is slowly becoming sleepy and less responsive. Physical exam reveals less wheezing than on admission. Representative lung histology is shown.
Introduction
  • Definition
    • episodic and reversible bronchoconstriction 
      • with bronchioles being the most susceptible respiratory segment
    • result of
      • inflammation
      • bronchial smooth muscle hypertrophy and hyperactivity
      • mucus plugging
Classification
  • Types
    • extrinsic
      • typically seen in children with a genetic predisposition
      • type I hypersensitivty to an inhaled (external) allergen such as pollen 
        • proceeds by specific stages
          • sensitization
            • CD4 TH2 cells produce cytokines (IL-4 and IL-5) when initially stimulated by an allergen 
              • IL-4 induces antibody isotype switch to IgE 
              • IL-5 induces eosinophil activation
          • early activation
            • mast cells are activated by cross-linking of IgE and release immune activating substances (histamine, leukotrienes, and acetylcholine) when allergen is presented again 
              • histamine results in bronchoconstriction, chemotaxis for immune cells, and mucus production
              • acetylcholine results in bronchoconstriction (parasympathetic mediated)
              • leukotrienes C4, D4, and E4 induce bronchoconstriction
          • late activation
            • eosinophils are activated    
              • recruited by eotaxin
              • produce major basic protein, which causes further constriction/damage in the airways  
    • intrinsic
      • non-allergen mediated
      • induced by
        • infection
          • viral URI (RSV, rhinovirus, and parainfluenza virus)
        • behavioral
          • exertion and stress
        • chemical
          • drug sensitivity (NSAIDs and aspirin)
          • ozone produced free-radicals
    • status asthmaticus
      • life-threatening asthma attack that does not respond to standard treatments
Presentation
  • Symptoms
    • wheezing
    • cough
    • mucus production
    • note: a child who is becoming sleepy and less responsive is most likely failing, retaining CO2 (case intro) and needs intubation
  • Physical exam
    • tachycardia
    • tachypnea with use of accessory muscles
      • result of reduced I/E ratio
      pulsus paradoxus
      • result of increased lung volume and vascular resistance
    • auscultation
      • prolonged expiratory wheezes (sometimes inspiratory)
      • high pitched sibilant rhonchi
      • dyspnea
      • persistent cough with hyperinflation of the lungs
Imaging
  • Chest radiograph
    • normal or hyperinflation
Studies
  • Labs
    • ABG
      • may initially show respiratory alkalosis
      • if CO2 is normal, respiratory failure may be imminent 
      • elevated CO2 (respiratory acidosis) are ominous signs and patient likely requires intubation
  • Pulmonary function tests 
    • peak flows are diminished
    • obstructive pattern may be seen when symptomatic (↓ FEV1/FVC)
      • improvement with bronchodilator administration
    • high airway resistance
  • Methacholine challenge   
    • provacative measure of hyperactivity in a well patient
    • functions as a muscarinic cholinergic agonist
    • reduction of FEV1 by > 20% is diagnostic of asthma
  • Skin testing
    • may result in hypersensitivity response to allergen when presented into skin (really diagnoses atopy, not asthma)
  • Histological changes 
    • terminal bronchioles
      • mucus plugs
        • Curschmann's spirals  
          • presence of trapped epithelial cells killed by eosinophil produced major basic protein
        • Charcot-Leyden crystals
          • aggregated eosinophils
      • increased mucus-producing cells
    • bronchi
      • thickened basement membrane
        • unique to asthma
      • hypertrophy of submucosal glands and smooth muscle
        • also seen in other lung disorders including chronic bronchitis
      • increased immune cell presence
 
Treatment
  • Acute exacerbation
    • oxygen
    • inhaled beta-2 agonists  
      • short acting preferred (e.g albuterol)
      • appropriate for exercise induced asthma
        • administer before exertion in known asthmatics
    • systemic corticosteroids (PO or IV)
  • Status asthmaticus
    • oxygen, bronchodilators, and steroids
    • sympathomimetic bronchodilators (e.g. epinephrine)
    • intubation and mechanical ventilation
  • Maintenance treatment
    • inhaled corticosteroids (mainstay)
    • long-acting bronchodilators (beta-2 agonists)
      • in combintation with inhaled corticosteroids (increased risk of death if used without inhaled corticosteroid)
    • montelukast
    • cromolyn
      • rarely used; supplemental treatment for exercise-induced asthma
    • theophylline
      • phosphodiesterase inhibitor; rarely used
    • ipratropium bromide
      • an anticholinergic that inhibits the contraction of smooth muscle
      • used in the elderly with an asthmatic component to their COPD
    • tiotropium
      • more recently shown to be efficacious and safe

Please rate topic.

Average 5.0 of 17 Ratings

Questions (14)
Evidence (17)
VIDEOS & PODCASTS (3)
EXPERT COMMENTS (5)
Private Note