Acute Bronchiolitis

Acute bronchiolitis is a viral lower respiratory tract infection of infants causing inflammation and obstruction of the small airways, with wheeze, crackles and respiratory distress.

• It affects children under 2 years, with a peak at 2 to 6 months, and is the commonest cause of admission in infancy.
• Respiratory syncytial virus causes most cases. Others include rhinovirus, human metapneumovirus, parainfluenza and adenovirus.
• Risk factors for severe disease include prematurity, age under 3 months, congenital heart disease, chronic lung disease, immunodeficiency, malnutrition and exposure to smoke.
• Illness peaks at day 3 to 5 and typically lasts 1 to 2 weeks. Cough may persist 3 weeks.

A coryzal prodrome leads to breathing difficulty.

• Runny nose, cough and low-grade fever for 1 to 3 days.
• Tachypnoea, nasal flaring, grunting and chest retractions.
• Wheeze and fine crackles on auscultation, hyperinflated chest.
• Poor feeding (under 50 percent of usual intake), vomiting and dehydration.
• Apnoea in young infants (especially under 6 weeks, premature).
• Severe: cyanosis, exhaustion, silent chest.
• Differential diagnosis: asthma or viral-induced wheeze (older infants), pneumonia, heart failure, foreign body, pertussis, aspiration, cystic fibrosis and vascular rings.
• Complications: respiratory failure, apnoea, dehydration, secondary bacterial infection, atelectasis, recurrent wheeze, and post-bronchiolitis cough.

Diagnosis is clinical.

• Assess respiratory rate, work of breathing, saturation (target above 92 percent), feeding and hydration.
• Routine chest X-ray is not needed. Order it if the course is atypical, severe, or a complication is suspected.
• Virology (nasopharyngeal aspirate) is only for infection control or cohorting.
• Blood gas for severe respiratory distress.
• Blood tests and cultures only if sepsis or secondary bacterial infection is suspected.

Treatment is supportive.

• Supportive: nasal suction, small frequent feeds, nasogastric or intravenous fluids if unable to feed (maintenance fluids at about two thirds of normal requirement to avoid hyponatraemia), humidified oxygen to keep saturation above 92 percent, and head-up positioning.
• Pharmacological: no routine bronchodilator, steroid, antibiotic or antiviral therapy. Antibiotics only for confirmed bacterial infection (for example amoxicillin 25 to 30 mg/kg every 8 hours or ampicillin 50 mg/kg every 6 hours).
• A supervised test dose of nebulised salbutamol 2.5 mg or hypertonic saline 3 percent, 4 mL, may be given in hospital with documented response; continue only if there is benefit.
• Respiratory support: high-flow nasal oxygen (2 L/kg/min), continuous positive airway pressure, or mechanical ventilation for respiratory failure or recurrent apnoea.
• Procedures: intubation and ventilation for failure of non-invasive support.
• Special groups: premature infants, congenital heart disease and immunodeficiency need low threshold for admission. Infants at high risk may receive palivizumab 15 mg/kg intramuscularly monthly during the season where available.
• Red flags: apnoea, cyanosis, severe retraction, saturation below 92 percent, feeding under 50 percent, age under 3 months, and exhaustion.
• Follow-up: discharge when feeding well and saturation above 92 percent in air. Review in primary care within 48 hours. Avoid smoke exposure. Return if worsening.