Bronchial asthma definition, risk factors, pathogenesis ?
Definition: a chronic inflammatory condition of the lung airways which is characterized by reversible airflow obstruction, easily triggered bronchospasms and recurring symptoms (cough, dyspnea and wheeze).
Risk factors of asthma:
- Usually starts in children < 6 years (80%)
- Usually associated with nasal allergy or gastro-oesophageal reflux disease (GERD)
- Other risk and triggering factors include environmental and genetic.
1. Environmental factors:
Allergens as pollens, mites, animal dander
Bacterial or viral respiratory infections
Pollutants as dust, smoke
Cold dry air, perfumes or irritant odour
Drugs as aspirin, beta-blockers
Excessive heat or humidity
Exercise
Urban life.
2. Biological and Genetic Risk
Family history of asthma
Family history of other allergies as: eczema, allergic rhinitis, or food allergy
Complex genetic disorder
An over-active gene “ORMDL3” was linked to 30% of childhood asthma (responsible for synthesis of sphingolipids)
Pathogenesis asthma : (Atopy or type I hypersensitivity)
- Exposure to asthma trigger: IgE-mediated allergens cause biphasic response
Early phase (within minutes) in the form of mast cell degranulation and airway changes (oedema, bronchospasm, and mucus secretion) → airway obstruction→ air trapping
Late phase (within 4-8 hours later)
Persistent airway inflammation → airway remodelling → persistent airways narrowing due to collagen deposition, smooth muscle hypertrophy and thickened basement membrane.
Bronchial asthma C/P, complications and investigations?
Clinical picture: either acute, chronic, acute on chronic
- Symptoms
o Recurrent attacks of dry irritative cough (worse at night, increased by exercise & change of weather with good response to bronchodilator, dyspnoea & wheezes (worse at night).
o Attacks may be induced by certain triggers.
o Comorbid atopic conditions, allergic rhinitis, eczema.
o In between attacks ~ the patient is either free or wheezing
- Signs:
General signs:
o Irritability and restlessness.
o Respiratory distress (tachypnea, retractions, grunting)
o In severe cases decreased movements and audible wheeze. In more severe episodes, patients may be unable to speak more than a few words without stopping for breath. Cyanosis is usually a late sign of hypoxia.
o Confusion and lethargy may indicate the onset of progressive respiratory failure.
o Less wheezing (silent chest) might indicate mucous plug or patient fatigue with less airflow. And it is a sign of impending respiratory failure fail
Local signs:
o Inspection: Hyper inflated chest and prolonged expiration.
o Palpation: May be palpable wheezes.
o Percussion: Bilateral hyperresonance.
o Auscultation: Diminished air entry with harsh vesicular breath sounds with prolonged expiration and bilateral expiratory wheezes.
Normal chest examination does not exclude asthma.
Complications
- In acute exacerbations:
o Pneumonia
o Pneumothorax
o Lung collapse
o Acute respiratory failure
- Long term sequels: chronic obstructive airway disease
Investigations (diagnosis mainly clinical)
- Chest x- ray: mainly to detect
o Complications as pneumonia, pneumothorax or collapse
or
o Hyperinflated chest and increased broncho vascular markings during acute attacks.
- Elevated IgE and eosinophils in the serum and sputum
- Lung functions tests: decreased peak Expiratory Volume (PEV or forced expiratory flow in the first second (FEV1). Done only for cooperative children above 5 years.
- Spirometry showing reversible airway obstruction
- FEV1/FVC below lower limit of normal adult : <0.75 to 0.8 in adults
- FEV1 improved more than 15%after bronchodilators
Classification of severity of acute asthma exacerbation?
Mild Vs severe
Altered consciousness: No VS Agitated, confused or drowsy
Oximetry on presentation(SaO2) **: > 95% VS < 92%
Speech: Sentences VS Words
Pulse rate: < 100 beats/min VS > 200 beats/min (0-3years) OR > 180 beats/min (4-5 years)
Respiratory Rate: < 40/minute VS > 40
Central cyanosis: Absent VS Likely to be present
Wheeze intensity: Variable VS Chest may be quiet
Differential diagnosis of asthma?
- Viral induced wheeze (recurrent bronchiolitis)
o Common in pre-school children
o Wheeze occurs with viruses only, and can occur for 2 years especially after RSV infection.
o No interval symptoms - Cystic fibrosis: if there are two or more pneumonias + poor growth + chronic cough + recurrent diarrhea
- Chronic cough + clubbing: → bronchiectasis, interstitial fibrosis, 1ry ciliary dyskinesia.
- Chronic sinusitis with +ve family history of male sterility: → cystic fibrosis, 1ry ciliary dyskinesia.
- Cough/ choking while feeding: chronic pulmonary aspiration.
- Sudden symptom onset of cough with history of choking: foreign body inhalation.
- History of prematurity: bronchopulmonary dysplasia.
- Habit cough (psychogenic) → a repetitive harsh barking cough that is absent once asleep.
GINA guidelines?
According to GINA guidelines children under 5 years of age need long term controller medications if they fulfil three of the following 4 criteria:
1. Symptoms (cough, wheeze and heavy breathing) > 10 days during URT infection
2. More than 3 episodes per year, or sever episodes and /or night worsening.
3. Between episodes child has cough, wheeze or heavy breathing during play or when laughing.
4. Child is suffering from other allergic diseases as eczema food allergy or family history of asthma.
Drugs used for treatment of bronchial asthma?
A. Relievers medications
1. Short acting selective B2 adrenergic agonist (SABA)
Inhaled short acting salbutamol, terbutaline, and Albuterol.
Side effects:
a. Agitation, irritability, and tremors.
b. Tachycardia, and even arrhythmias
c. Hyperglycinemia and hypokalaemia in high doses
2. Inhaled short acting muscarinic antagonist (SAMA):
Ipratropium bromide (used in ER) → parasympatholytic
Side effects: mild atropine like effects.
3. Short course of systemic steroids for around 4 days.
B. Controller medications:
a. Inhaled Steroids:
Forms: beclomethasone, budesonide, fluticasone)
Mechanism of actions: anti-inflammatory effect and enhance the action of b2 agonist on the bronchial receptors
Side effects:
o Oral moniliasis and dysphonia.
o Prolonged high dose may cause adrenal suppression.
o Long term use may affect the ultimate height.
b. Long acting selective B2 adrenergic agonist (LABA) Never used alone (used with steroids)
Include salmeterol (> 4 years) and formoterol (> 6 years)
Same side effects as SABA
c. Leukotriene receptor antagonist (LTRA) like Montelukast
It is given oral as a showable tablet or as sachets.
Block the inflammatory mediators→ bronchodilatation
Can treat allergies and bronchial asthma (adjunctive to inhaled steroids)
d. Mast cell stabilizer like Na cromoglycate which is given by inhalation (Spnihaler)
e. Theophylline (sustained release:)
Mechanism of action: relaxation of smooth muscles via increase cAMP
Side effects: convulsions, GIT upset, and tachycardia
How to deal with a case of acute asthma?
Therapy + Dose and Administration
- Supplemental oxygen: By face mask (usually 1 L/min) to maintain oxygen saturation 94-98%.
- Inhaled SABA: 2-6 puffs of salbutamol by spacer, or 2.5 mg by nebulizer, every 20 min for first hour, then reassess severity. If symptoms persist or recur, give an additional 2-3 puffs or nebulized salbutamol per hour. Admit to hospital if >10 puffs required in 3-4 hours.
- Ipratropium bromide: For moderate/severe exacerbations, add 250 µg Ipratropium bromide to nebulized salbutamol from the start and repeat every 20 minutes for one hour only.
- Nebulized Steroids (Budesonide): Added to nebulized salbutamol in moderate and severe exacerbations.
- Systemic corticosteroids: Give initial dose of oral prednisolone (1-2 mg/kg/d) or IV Methylprednisolone 1 mg/kg every 6 hours.
Additional options in the first hour of treatment
Magnesium sulfate: Consider nebulized isotonic MgSO₄ (150 mg), 3 doses in first hour for children ≥2 years with severe exacerbation.
IV MgSO₄ Single dose 40-50 mg/kg (max 2 g) over 20-60 minutes.
Status asthmaticus definition, C/P and management
Definition: Increasingly severe asthma not responding to standard therapy
Clinical picture:
The same as acute severe asthma with signs of respiratory failure (confusion, bradycardia, paradoxical thoraco-abdominal respiration, absent wheeze, cyanosis).
Management
Admission to ICU
Monitoring of RR, pulse, cyanosis and chest signs.
X-ray chest to exclude complication like pneumothorax, PEFR and ABG9s
High flow oxygen to keep O2 saturation > 92% O2
IV maintenance fluids: 70-80% of maintenance (add Kcl as B2 agonists lead to hypokalaemia). Correct any dehydration
Bronchodilators: Salbutamol nebulizer can be delivered frequently (every 20 min to 1 hr) or continuously. Ipratropium bromide 250 mg is added to SABA (3 doses) to cause synergistic action.
Nebulized isotonic Magnesium Sulphate (3 doses) every /20 minute for one hour
Parenteral steroids (IV methyl prednisolone or hydrocortisone) followed by short term oral steroids.
Parenteral antibiotics for 2ry bacterial infection.
In case of failure to respond to above lines we have 4 options
o IV Salbutamol
o Mg Sulphate IV infusion over one hour.
o Aminophylline continuous IV infusion 1mg/kg/h
o Mechanical ventilation the last option: indicated in respiratory failure, cyanosis or marked decrease of PaO2.
After exacerbation resolution:
o Continue inhaled SABA every 4 to 6 hours until patient improve then stop
o Start controller therapy
Management of chronic asthma
- Confirm diagnosis (mainly clinical) and identify triggers.
- Determine severity (table 3)
- Parent and patient9s education about medications, devices and how to use.
- Parent and patient9s education about prevention of asthma by:
Avoiding triggering agent through:
o Eliminate triggering factors.
o Avoid allergens as suggested by skin testing.
Treat comorbidities as: sinusitis, rhinitis, and GERD.
Give annual influenza vaccines.
Prophylaxis of exercise induced asthma by SABA or Na cromoglycate inhalation before exercise plus LTRA (Montelukast) prophylaxis for at least 3 months. - Start with Stepwise approach for long-term asthma therapy
- Establish follow up schedule:
o Every 2 to 6 weeks while establishing control.
o Every 3 months if stepdown therapy desired.
