14. BRONCHIAL ASTHMA Flashcards
Diagnostic algorithm:
Positive bronchodilator response (+12% or 200 mL of FEV1)
Positive challenging test (-15% of FEV1)
Positive specific IgE against Inhaled allergens
Increased total IgE
Positive allergy skin tests (dust, pollen, mould, domestic animals)
Increased eosinophil counts in blood, sputum or bronchoalveolar lavage
Elevated levels of nitric oxide in exhaled air
Radiological findings associated with asthma comlications:
- Complications - atelectasis, pneumothorax, pneumomediatinum
- Radiographic findings - bilateral pulmonary hyperinflation, flat and lowset diaphragm, wide intercostal spaces, enlarged and compact hilar shadows
Treatment of acute asthma attack:
- 3 inhalations of salbutamol every 20 minutes for one hour using a metered dose inhaler with spacer - 2-4 sprays, or a nebulizer with a dose 0.15-0.3mg/kg (0.03-0.06mL/kg) + 3mL saline
-> upon discharge may need to continue therapy at 4-6 hour intervals
Treatment of moderate and severe asthma attack:
- Oxygen supply - 2-4L/min
- Triple nebulizer inhalations with a B2-agonist + fast acting anticholinergic (Ipratropium bromide, Atrovent) 250ug 1mL and systemic administration (oral or parenteral) of methylprednisolone 1-2mg/kg -> continue at 12 hour intervals
- If necessary -> shorten intervals between inhalations or continuous long-term inhalation of Salbutamol (0.5mg/kg/h or 10-60mg/h)
+ parenteral administration of fast acting b2-agonists, parenteral administration of methylxanthines, IV magnesium sulphate
Avoid in pediatric asthma attack:
Sedatives - strictly avoid
Mucolytic - may increase cough
Physiotherapy - can increase discomfort
High volume hydration in children and adults - may be necessary in infants and small children
Antibiotics
Long-term asthma control medications:
- Inhlaed corticosteroids - Reduce symptoms and exacerbations, prevent respiratory remodelling and reduce the morbidity and mortality
** have powerful anti-inflammatory effect, reduce bronchial hyperresponsiveness, reduce mucouc secretion, reduce mucsal swelling, increase beta receptors in lungs, increase sensativity to beta agonists
** osteoperosis, cataracts, glaucoma, impaired bone growth, oropharyngeal candidiasis, dysphonia, cough, throat irritation
Cromolyn-related drugs have anti-inflammatory effects associated with the stabilization of the mast cell membrane
Antileukotrienes
Omalizumab - monoclonal human antibody that neutralizes IgE
Step-by-step control of asthma:
Mild - well controlled in step 1 or 2 (short acting b-agonists or low dose ICS if needed)
Moderate - well controlled in step 3 (low dose combination of ICS/long-acting B-agonists)
Severe - step 4 or 5 (moderate or high dose combination of ICS/long-actng B-agonists + other controlling drugs)
Leukotrienes, synthesized via the arachidonic acid metabolism cascade, are potent mediators of inflammation and smooth muscle bronchoconstriction.
Leukotriene modifiers are oral, daily-use medications that inhibit these biologic effects in the airway.
Two classes of leukotriene modifiers include cysteinyl leukotriene receptor antagonists (zafirlukast and montelukast) and leukotriene synthesis inhibitors (zileuton).
Zafirlukast is approved for children older than 5 years of age and is given twice daily.
Montelukast is dosed once daily, at night, as 4-mg granules or chewable tablets (for children 6 months to 5 years), 5-mg chewable tablets (6 to 14 years), and 10-mg tablets (15 years of age or older).
Pediatric studies show the usefulness of leukotriene modifiers in mild asthma and the attenuation of exercise-induced bronchoconstriction. These agents may be helpful as steroid-sparing agents in patients with asthma that is more difficult to control.
Long acting beta 2 agonists:
Long-acting β2-agonists, formoterol and salmeterol, have twice-daily dosing and relax airway smooth muscle for 12 hours but do not have any significant anti-inflammatory effects.
Adding a long-acting bronchodilator to inhaled corticosteroid therapy is more beneficial than doubling the dose of inhaled corticosteroids. Multiple formulations are available.
Formoterol is approved for use in children older than 5 years of age for maintenance asthma therapy and for prevention of exercise-induced asthma. It has a rapid onset of action similar to albuterol (15 minutes).
Salmeterol is approved for children 4 years of age or older and has an onset of 30 minutes. Because combination agents administer two medications simultaneously, compliance is generally improved.
Short acting beta-2 agonists:
Short-acting β2-agonists, such as albuterol, levalbuterol, and pirbuterol, are effective bronchodilators that exert their effect by relaxing bronchial smooth muscle within 5 to 10 minutes of administration.
They last for 4 to 6 hours. Generally, a short-acting β2-agonist is prescribed for acute symptoms and as prophylaxis before allergen exposure and exercise.
The inhaled route is preferred because adverse effects—tremor, prolonged tachycardia, and irritability—are less.
Overuse of β2-agonists implies inadequate control; a change in medications may be warranted.
The definition of overuse depends on the severity of the child’s asthma; use of more than one metered dose inhaler canister per month or more than eight puffs per day suggests poor control.
Oral corticosteroids:
Short bursts of oral corticosteroids (3 to 10 days) are administered to children with acute exacerbations.
The initial starting dose is 1 to 2 mg/kg/day of prednisone followed by 1 mg/kg/day over the next 2 to 5 days.
Oral corticosteroids are available in liquid or tablet formulations.
Prolonged use of oral corticosteroids can result in systemic adverse effects such as hypothalamic-pituitary-adrenal suppression, cushingoid features, weight gain, hypertension, diabetes, cataracts, glaucoma, osteoporosis, and growth suppression.
Children with severe asthma may require oral corticosteroids over extended periods. The dose should be tapered as soon as possible to the minimum effective dose, preferably administered on alternate days.
