To most persons, asthma means wheezing regardless of its cause. As per American thoracic society definition, Asthma is defined as "a disease characterized by an increased responsiveness of the trachea and bronchi to various stimuli and manifested by narrowing of the air ways that changes in severity either spontaneously or as a result of treatment". Essentially, asthma is a reversible airways obstruction.
Incidence :
Estimates or prevalence ranges from less than 1% up to more than 12%. In school going children it is around 1 to 2%; male predominance.
Factors Related to Asthma :
1. Family history of hypersensitivity state in 50-75% of cases.
2. Allergy - 50% of children with Eczema or atrophy develop asthma. 30% of children with hay fever/allergic rhinitis develop asthma. Environmental allergens such as food allergens, house dust mite and pollen etc. may be a factor.
3. Infection especially viral or bacterial may precipitate an attack of asthma.
4. Psychotic factors - Asthmatic children are highly emotional, react significantly to various emotional states.
5. Exercise may induce asthmatic attacks in susceptible persons.
6. Pollution and climatic variations may initiate an attack.
Pathogenesis:
Two main hypothesis have been put forward :
a) Asthma is primarily due to immunological disorders. Different immunological mechanism being involved to explain different aspects of Asthma of which the most important is type I hypersensitivity reaction, mediated through IgE and mast cells.
b) Asthma is primarily due to bronchial hyper reactivity. The result of imbalance of autonomic control of bronchial caliber.
Clinical Features :
The symptoms may range from the mild wheeze to the most severe respiratory distress. Age is an important conditioning factor in the presentation of a child with asthma. The onset of an asthmatic paroxysm is usually sudden and often occurs at night. There may be history of chest tightness and a husking unproductive cough. A typical attacks consists of marked dyspnoea, bouts of cough and chiefly expiratory wheeze. Depending on the degree of severity there may be chest recession and difficulty in speaking due to shallow breathing.
Physical signs are rapid labored respiration with audible wheeze and prolonged expiration. Hyper inflated chest with intercostal, subcostal recession. Hyper resonant lung fields. Vesicular breath sound with prolonged expiration and expiratory bronchi. There is usually tachycardia and tachypnoea. Cyanosis may be present.
Differential Diagnosis :
1. Bronchitis
2. Bronchiolitis
3. Inhalation of foreign body
4. Whooping cough
5. Lobar emphysema
6. Acute laryngio tracheo bronchitis
7. Pneumonia
Complications:
1. Emphysema
2. Collapse
3. Consolidation
4. Pneumothorax
5. Bronchiectasis
Treatments:
During acute attacks, the management is aimed at alleviating the paroxysm and relief of bronchospasm by bronchodilators either by sympathomimetic amines or xanthine derivatives. Choices of drugs also depend on the severity of bronchospasm.
Mild wheezing :
Theophylline may be used orally in doses of 20 mg/kg/24 hours in 3 divided doses or orciprenalline orally 2.0 mg/kg/24 hours 3 divided doses. Salbutamol is most commonly used bronchodilator in mild attacks.
Moderate to severe wheezing :
Aminophylline intravenously in loading dose 4-6 mg/kg diluted 4 fold in saline I.V. slowly maintenance, 15 mg/kg/24 hour or 0.9 mg/kg/hour intravenous infusion. Salbutamol intravenously may also be used in a dose of 2.5 - 5 mg/kg/ I.V. hourly.
Aerosolized adrenergic agents (Isoprenalol or salbutamal) by hand or pressurized nebulizer are of help in controlling the acute paroxysm.
Nebulised salbutamol respiratory solution (5mg/ml) in a dose of 0.01 to 0.03ml/kg salbutamol solution diluted to 2ml with distilled water via nebulizer 4 to 6 hourly.
Additional Measures are to be taken :
1. Antibiotic may be given if suspected of infection
2. Oxygen inhalation in case of marked respiratory difficulty or cyanosis.
3. Maintenance of fluid and electrolyte balance, correct acidosis with sodium bicarbonate.
4. Steroid, for short period only are particularly indicated in children, who continue to be in status asthmatics.
Suitable oral dosage of prednisolone is 5 mg 4 times in first 24 hours, 10 mg in 4 times in 2nd 24 hours and gradually tapering dose.
In dire emergency hydrocortisone sodium succinate may be given intravenously in a six hourly doses of 100 to 200 mg for 24 hours, to be followed by oral steroid for another 2 to 3 days. Corticosteroid can also be used in bronchial asthma as nebulized form as inhalation for its local effect.
Long Term Management:
The aim of long term management in asthma is prevent or reduce the frequency and severity of acute attacks of bronchospasm. In recent years few new development in drug therapy has changed the long term management. The first of these is sodium cromoglycale (Intal). It is taken as spininhaler. This drug inhibits the release of vasoactive amines from mast cells and reduces the frequency of asthmatic attacks. Initial should be used prophylactically for 3-6 months.
The availability of Ketotifen has similar mechanism of action of inhibiting the type 1 hyper sensitivity reaction and can be given orally.
The other form of drug therapy which has proven extremely effective by esterification of betamethasone which yields a steroid with marked topical anti-inflammatory properties. The recommended dose of Beclomethasone 50-100 micro gram 2 to 4 times daily and Betamethasone 100 - 200 micro gram (1-2 puffs) 2 to 4 times daily if proven efficacy in chronic asthmatics.
Desensitization to the various allergens being used with limited success. The psychological management of the child with chronic asthma is most important.
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