Asthma Flashcards
Define
chronic inflammatory airway disease characterised by
- variable reversible airway obstruction
- airway hyper-responsiveness
- bronchial inflammation
Characterised by recurrent episodes of dyspnoea, cough and wheeze – Caused by reversible airways obstruction
Causes
Genetic Factors
- Family history
- Atopy (tendency for T lymphocytes to drive production of IgE on exposure to allergens)
Environmental Factors
- House dust mites
- Pollen
- Pets
- Cigarette smoke
- Viral respiratory tract infections
- Aspergillus fumigatus spores
- Occupational allergens
Epidemiology
Often young onset, F=M
Affects 10% of children, 5% of adults
Prevalence is increasing
Acute asthma is a very common medical emergency
Symptoms
- Dyspnoea
- Episodes of wheeze
- Cough (nocturnal)
- Sputum
Worse in morning and at night
Ask about precipitants (cold air, exercise, emotion, allergens, infection, smoking, NSAIDs, β-block, pollution); exercise tolerance; disturbed sleep (severe); acid reflux; other atopic diseases (eczema, allergies)
Signs
- Tachypnoea
- Use of accessory muscles
- Prolonged expiratory phase
- Polyphonic wheeze
- Hyperinflated chest
Severe Attack
- PEFR < 50% predicted
- Pulse > 110/min
- RR > 25/min
- Inability to complete sentences
Life-Threatening Attack
- PEFR < 33% predicted
- Silent chest
- Cyanosis
- Bradycardia
- Hypotension
- Confusion
- Coma
Investigations
ACUTE
- Peak flow
- Pulse oximetry
- ABG
- CXR - to exclude other diagnoses (e.g. pneumonia, pneumothorax)
- FBC - raised WCC if infective exacerbation
- CRP
- U&Es
- Blood and sputum cultures
CHRONIC
- Peak flow monitoring - often shows diurnal variation with a dip in the morning
- Pulmonary function test
- Bloods - check:
- Eosinophilia
- IgE level
- Aspergillus antibody titres
- Skin prick tests - helps identify allergens
Management
ACUTE
- ABCDE
- Resuscitate
- Monitor O2 sats, ABG and PEFR
- High-flow oxygen
- Salbutamol nebulizer (5 mg, initially continuously, then 2-4 hourly)
- Ipratropium bromide (0.5 mg QDS)
- Steroid therapy
- 100-200 mg IV hydrocortisone
- Followed by, 40 mg oral prednisolone for 5-7 days
- If no improvement –> IV magnesium sulphate
- Consider IV aminophylline infusion
- Consider IV salbutamol
- Treat underlying cause (e.g. infection - AB)
- Monitor electrolytes closely because bronchodilators and aminophylline causes a drop in K+
DISCHARGE when:
- PEF > 75% predicted
- Diurnal variation < 25%
CHRONIC THERAPY
Start on step appropriate to initial severity then step up or down
- Inhaled short acting β2 agonist (salbutamol)
- Add inhaled low-dose corticosteroid (beclomethasone)
- Add inhaled long acting β2 agonist (salmeterol)
- Increase the steroid dose
- Add leukotriene receptor antagonist (Montelukast or theophylline)
- Addition of regular oral steroids, maintain high-dose inhaled steroid, anticholinergics (ipratropium), refer to specialist
Complications
Growth retardation (small for age); chest wall deformation (pigeon chest); recurrent infections; pneumothorax; respiratory failure; death
Prognosis
Many children improve as they grow older
Adult-onset is usually chronic
