PAEDIATRIC ASTHMA:

RELATED PAGES: PreSchool Asthma Outcome Preschool Asthma Role of Allergy in Asthma

DEFINITION

• Periodic or persistent symptoms of Cough, wheeze, dyspnoea
• Variable airflow limitation
• Variable airway hyperreactivity
• Associated airway inflammation, especially eosinophilic.

POINTS

• Trend is to use objective measures for diagnosis but that is not routinely possible in children under age five.
• Asthma in preschool children is different from asthma in older children.
• Allergy is the only mechanism for creating eosinophilic inflammation – must diagnose allergy.

INFLAMMATION IN ASTHMA

Inflammation or angriness in the tubes to the lungs (airways) is now thought to be the underlying cause of asthma. The inflammation consists of activated eosinophils, lymphocytes, increased numbers of mast cells and increased mucous formation. The role of neutrophils are less well understood. The presence of inflammation has been established by:

• Bronchoalveolar lavage and bronchoscopy
• Airway biopsies
• Induced sputum

EOSINOPHILIC INFLAMMATION

The presence of eosinophils:

1. leads to airway remodelling.
2. airway remodelling leads to airway hyperreactivity.
3. airway inflammation plus airway hyperreactivity lead to clinical symptoms.

FACTORS THAT INDUCE INFLAMMATION

• VIRAL ILLNESSES
• ALLERGY
• ENVIRONMENTAL TOBACCO SMOKE

FACTORS THAT IRRITATE AIRWAYS THAT ARE ALREADY INFLAMED

• Diurnal Variation (night & morning)
• Exercise
• Cold Air
• Strong Odours

ALLERGY IN PEDIATRIC ASTHMA

Allergy creates eosinophilic inflammation and in children is virtually the only mechanism for creating eosinophilic inflammation. Viral illnesses and Pollution increase the level of pre-existing eosinophilic inflammation. The most important allergens for asthma are the indoor allergens: pets, mites, moulds and cockroaches. Sensitivity to pollens is less important in asthma unless the asthma is already poorly controlled. Asthma under age 3 is often non-allergic and if the child remains non-allergic, he/she has a good chance of outgrowing the asthma as he/she gets older and develop fewer viral illnesses. Atopic asthma is more likely to persist.

Diagnosis of ALLERGY

The allergic child can be recognized from the following pieces of history:

• Significant eczema as an Infant
• Immediate reaction to food as an infant, especially milk, egg, peanut, nuts.
• Symptoms of allergic rhinitis such as rhinorrhea, sneezing, rubbing of the nose without a cold.
• Seasonal variation in rhinitis
• Immediate symptoms around animals

Allergy Control in the home

The most important controls are:

• Dust mite control in Bedroom - especially mite barriers completely encasing the mattress and pillows, absence of a carpet in the bedroom.
• No furry pets or birds in home. (Less optimal - wash pet weekly; no rugs or upholstered furniture in home; HEPA filter in bedroom.)
• Mould check i.e for wet areas, basement, bathrooms and kitchen.

School age Asthma

• Majority are atopic
• Potentially Chronic
• More Difficult to outgrow
• Treat: inhaled corticosteroid at lowest dose with Action Plan

Diagnosis of School-Age Asthma

• History: Recurrent wheeze or cough usually with each cold. Cough or wheeze between colds. Symptoms with exercise.
• Spirometry or Peak Flows: Variable FEV1 or peak flow (spirometry).
• Airway Hyperreactivity: Methacholine or Histamine Challenge.

Differential diagnosis in school-age asthma

Asthma is by far the commonest cause of persisting cough, wheeze and/ or shortness of breath.

• Findings on Physical Examination would suggest the need for a Chest xray
• History of reflux: heartburn etc. would suggest acid-reflux.
• History of paroxysmal cough would suggest pertussis-like illness.
• History of bacterial infections would suggest immune system problem.
• Poor response to medication would suggest the need to explore other diagnoses.
• Hyperventilation

Preschool asthma

• cough and wheeze is heterogeneous
• consider other causes
• majority will outgrow
• majority are non-atopic, viral induced
• passive cigarette smoke creates persist
• Atopy is associated with persistence

Pathophysiology of preschool asthma

• pathophysiology of nonatopic viral -unknown
• There is data that some, usually boys born with small airways
• 1 study done with bronchial lavage found non-eosinophilic cellular infiltrate.
• several studies have shown that non-atopic wheezers have lower peripheral eosinophils and serum ECP

Diagnosis of Preschool Asthma

• Wheeze plus cough especially with viral infections.
• ask for personal atopic history.
• ask for family history of asthma/atopy

Differential diagnosis in preschool asthma

• Neonatal onset suggests need for investigation.
• Failure to thrive suggests need for investigation.
• Chronic infection suggests diagnosis other than asthma.
• Vomiting, spitting up excessively suggest acid-reflux.
• Choking, Cyanotic episodes suggests compression of trachea.
• Focal lung or Cardiovascular signs suggests need for investigation.

Preschool asthma - RECOMMENDATIONS

• Prognosis differs between atopic vs non-atopic viral-induced asthma.
• attempt to identify atopy by family history; history of personal allergy; skin testing.
• in the presence of atopy, manage as per older children.
• Passive smoking increases cough and wheeze. Must be no smoking in homes or cars.
• Asthma that is chronic or with hospitalization or visits to emergency or courses of oral steroid - manage with inhaled steroid and prn bronchodilator.
• Mild chronic asthma start on low-dose inhaled steroid.
• episodic viral induced asthma in non-atopics does not require maintenance inhaled steroid and can be managed with intermittent inhaled steroid begun at the first sign of a cold.

THERAPY IN PEDIATRIC ASTHMA:

Trial of Therapy.

NOTHING WORKS AS WELL IN ASTHMA AS INHALED STEROID!

Trial of Therapy: Failure

1. Patient is Not Getting the Medication.
2. The diagnosis is Not Asthma
3. The diagnosis is correct but there is more asthma than estimated.

Steroid in Pediatric Asthma

steroid in asthma

• acts at multiple levels
• acts to suppress eosinophil inflammation
• acts at gene level to suppress cytokines

steroid in asthma

• new generation
• high lipid soluble
• high affinity for receptor
• prolonged contact time in lung
• rapid metabolism when absorbed

STEROID IN ASTHMA: Beneficial Effects

• reduces airway inflammation
• increases airway function
• decreases airway secretions
• decreases airway reactivity
• restores airway integrity
• probable effect on goblet cells & mucus

steroid in asthma

• improve airway inflammation
• improve airway hyperresponsiveness
• improve airflow obstruction
• improve symptoms
• only medication which has been shown to prevent the decline in lung function
• only medication which has been shown to prevent the development of fixed airflow obstruction

inhaled steroids in Pediatric asthma

• lung function increased as the child aged, to a greater degree when treated with inhaled steroid (Budesonide) compared to all other therapies.
• improvement greatest the sooner (Budesonide) was started after diagnosis.

They found symptom control and improvement in peak flows occurs rapidly in 1 - 2 weeks at low dose - 100 mcg per day. Longer treatment at higher doses ( 400 - 600 mcg) for months was required to change airway hyperreactivity and exercise induced asthma symptoms.

Inhaled steroid Effect on HPA axis

• Depends on the sensitivity of the measure
• Differs between types and delivery system
• More effect the higher the dose
• No clinically relevant effects at 400mcg or less
• Idiosyncratic

safety of inhaled steroids in Pediatric Asthma

Effect on Growth:

• 3 double blind- placebo controlled studies that beclomethasone 400 mcg reduces growth by 1 cm per year in mild asthma.
• the growth retarding effect occurs in the first months of treatment, then no further but no catch-up.

HOWEVER Agertoft and Pedersen have now published a 12 year follow-up from childhood to adulthood and have found that the children who achieved their predicted adult height were those who were treated with inhaled steroid (budesonide, average dose of 400 mcg. per day). The children who failed to achieve predicted adult height did so because of poor lung volumes. They concluded that the initial interference with growth as the child is started on inhaled steroid is not maintained and does not interfere with achieving a normal final height. However late introduction of inhaled steroid can lead to poor lung outcome in asthma which in turn can interfere with growth.

Go to Agertoft and Pedersen

Effect on Bone mineral Density:

• no indication that long term use is associated with increased osteoporosis or fractures
• standard pediatric doses are not associated with changes in biochemical markers of bone formation or degradation.
• oral prednisone 2.5 - 5 mg/day adversely affects these markers.

Pediatric Asthma: inhaled steroid - CONCLUSIONS:

1. nothing works as well as inhaled steroid
2. no free lunch - there can be side effects
3. achieve control and then use the least amount
4. majority can be treated with safe doses

CANADIAN GUIDELINES

Recommend: That asthma treatment be started with an amount of inhaled steroid sufficient to achieve full control and then the dose is decreased to the minimum necessary for maintenance of control. An action plan should be provided so that at the first sign of symptoms, the dose of inhaled steroid is increased and a short-acting bronchodilator is added as needed for quick relief. Non-steroidal anti-inflammatory medications are not recommended as monotherapy for asthma but can be used as add on therapy to try to lower the dose of inhaled steroid.

This style of management can be seen in the Asthma Continuum figure below.

POST-INFECTIOUS COUGH

• often begins with paroxysmal cough i.e. pertussis-like. The paroxysms last 6-8 weeks and are followed by a persisting non-paroxysmal cough.
• often occurs in children who cough with most colds.
• paroxysms respond poorly to any medication.
• persisting non-paroxysmal cough may respond to inhaled steroid.

Pediatric Asthma: Compliance

• POOR ADHERENCE TO ASTHMA MEDICATION REGIMENS REPEATEDLY DEMONSTRATED IN CHILDREN AND ADULTS.
• RATE OF NONADHERENCE IN VARIOUS REPORTS: 30 - 70%

COMPLIANCE MONITORING (ADULTS)

Rand and Colleagues performed a clinical trial of monitored inhaled medication to be used as 2 puffs three times per day by and compliance was judged by self-report; canister weight and Chronolog (microprocessor)

RESULT:

1. Self-report - 75% used three times per day.
2. Chronolog - 15% used 2.5x per day or more.
3. 14% activated puffers >100 times in 3 hrs.

They concluded that compliance was poor even in a study.