Bronchiolitis in Children

Bronchiolitis is an acute infectious disease of the lower respiratory tract that occurs primarily in those aged between 2 months and 2 years, especially young infants. It is usually due to a viral infection of the bronchioles. A combination of increased mucus production, cell debris and oedema produces narrowing and obstruction of small airways.

• Respiratory synctial virus (RSV) is the most common pathogen¹
• Adenovirus (11%) - occasionally causes a similar syndrome with a more virulent course
• Parainfluenza virus
• Other less common causes include:
  • Mycoplasma pneumoniae
  • Enterovirus
  • Influenza virus
  • Rhinovirus
  • Chlamydia pneumoniae

• Peak incidence of RSV infections is in the winter months, although the size of the peak varies from winter to winter.¹
• Prevalence may be higher in urban areas.
• Over 60% of children have been infected by their first birthday, and over 80% by two years of age. The antibodies that develop following early childhood infection do not prevent further RSV infections throughout life.¹
• Incidence peaks in those aged 2-8 months.

Symptoms

• Early symptoms are those of a viral URTI, including mild rhinorrhoea, cough, and fever (50% will have a temperature >38.5 °C)²
• Adults, older children and many infants do not progress to any further symptoms
• For the 40% of infants and young children who progress to lower respiratory tract involvement, paroxysmal cough and dyspnoea develop within 1-2 days.
• Other common symptoms include the following fever, wheeze, cyanosis, vomiting, irritability and poor feeding
• Apnoea may occur, especially in young infants

Signs

• General signs: tachypnoea, tachycardia, fever, cyanosis, may be dehydrated.
• Mild conjunctivitis, pharyngitis.
• Diffuse expiratory wheezing, nasal flaring, intercostal recession, inspiratory crepitations.
• Liver and spleen may be palpable (hyperinflation of the lungs).

• Asthma and other causes of wheezing in childhood
• Bronchitis
• Pulmonary oedema
• Foreign body inhalation
• Pneumonia
• Oesophageal reflux
• Aspiration
• Cystic fibrosis
• Kartagener's syndrome
• Tracheomalacia/bronchomalacia
• Pneumothorax

• Oximetry
• Nasopharyngeal aspirate for:
  • RSV immunofluorescence
  • Viral cultures for RSV (less sensitive (60%) but are 100% specific³), influenza A & B, parainfluenza and adenovirus
• Chest x-ray: non-specific hyperinflation and patchy infiltrates; focal atelectasis; air trapping; flattened diaphragm; increased antero-posterior diameter; peri-bronchial cuffing. Chest x-ray is also important in considering differential diagnoses.
• Full blood count: white cell count is usually within normal limits (if significant neutrophilia with focal radiological changes consider bacterial pneumonia).
• Electrolytes and renal function if dehydrated or on IV fluids
• Blood culture if temperature >38.5 °C
• Arterial blood gases: may be required in the severely ill patients, especially those requiring mechanical ventilation

• General supportive measures are the mainstay of treatment, with attention to fluid input, nutrition and temperature control.
• Hospital admission is required for moderate and severe cases of bronchiolitis or where there is dehydration, a history of apnoea before presentation, pre-existing cardiac anomaly or lung disease, prematurity, age <2 months, or if home care/rapid review cannot be assured.
• ICU admission is necessary if the child has increasing severe respiratory distress with desaturation or apnoea whilst receiving 50% O₂. CPAP or intubation may be required in these cases.
• Bronchodilators produce only a clinically non-relevant, modest short-term improvement in clinical scores, but no improvement in SaO₂ or hospitalisation rate. Ipratropium bromide has no short term benefit.⁴
• Ribavirin may reduce the need for mechanical ventilatory support and the number of days in hospital, and may be associated with a decrease in the long-term incidence of recurrent wheezing following RSV induced lower respiratory tract infection.⁵ However, there is no clear evidence that ribavirin produces clinically relevant benefit in RSV bronchiolitis.
• Palivizumab, a monclonal antibody therapy, is licensed in the UK for the prevention of serious lower respiratory tract infection caused by RSV in infants at high risk of infection. The first dose should be administered before the start of the RSV season.
• Further care for those requiring hospital admission includes careful monitoring, including pulse oximetry and humidified oxygen.
• Antibiotics are not indicated unless there is evidence or suspicion of a co-existing bacterial infection.
• Systemic glucocorticoids do not appear to have a clinically significant effect on the course of acute viral bronchiolitis in infants and young children.⁶ However outpatients with moderate-to-severe acute bronchiolitis derive significant benefit from oral dexamethasone treatment in the initial 4 hours of therapy.⁷
• Chest physiotherapy does not reduce the length of hospital stay and its role in management is still being evaluated.⁸

• Most children with bronchiolitis make a full recovery. The course of disease is usually 7-10 days, but a few remain unwell for weeks.
• Hospital admission is required in up to 2% of cases; most of those patients are younger than 6 months.³
• Mechanical ventilation is required for 3-7% of admitted patients.²
• Mortality rate is 1-2% of all hospitalized patients and 3-4% for patients with underlying cardiac or pulmonary disease.³
• Most deaths occur in infants younger than 6 months.