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Bronchiolitis

Basics

  • Inflammation and obstruction of small airways in infants and young children (<2 years, peak <6 months)
  • URI prodrome followed by respiratory distress, wheezing, crackles
  • Insidious, acute, progressive course lasting 14-21 days in some

Epidemiology

  • Leading cause of hospitalization in infants/children in Western countries
  • Incidence: 3.2/1,000 children
  • RSV accounts for 70-85% of cases <12 months
  • Almost all children infected with RSV by age 2
  • Seasonal in temperate regions (Oct-May), year-round in subtropics

Etiology and Pathophysiology

  • Most commonly caused by respiratory syncytial virus (RSV)
  • Other viruses: rhinovirus, parainfluenza, metapneumovirus, adenovirus, influenza
  • Infection causes epithelial necrosis, inflammation, edema, mucus accumulation β†’ airway obstruction
  • Air trapping due to dynamic airway narrowing on expiration
  • Bronchospasm minimal or absent

Risk Factors

  • Prematurity (<35 weeks gestation), low birth weight
  • Secondhand smoke exposure
  • Immunodeficiency
  • Formula feeding
  • Daycare exposure
  • Congenital cardiopulmonary or neurologic diseases
  • Age <12 weeks

Prevention

  • Hand hygiene with alcohol-based rubs preferred
  • Contact isolation for infected infants
  • Limit exposure to sick contacts
  • Breastfeeding β‰₯6 months reduces severity
  • Palivizumab (15 mg/kg IM monthly Oct-May) for high-risk infants (per AAP guidelines)

Common Associated Conditions

  • URI symptoms (rhinorrhea, pharyngitis, conjunctivitis, otitis media)
  • Diarrhea

Diagnosis

History

  • URI symptoms: irritability, anorexia, fever, noisy breathing, cough, grunting, cyanosis, apnea, vomiting

Physical Exam

  • Tachypnea, retractions, wheezing, crackles
  • Signs of URI (pharyngitis, conjunctivitis, otitis)

Differential Diagnosis

  • Pertussis, croup, bacterial pneumonia
  • Aspiration, foreign body, vascular ring
  • Asthma, heart failure, GERD, cystic fibrosis

Diagnostic Testing

  • Clinical diagnosis primarily; labs and imaging usually unnecessary
  • Pulse oximetry: interpret in clinical context; transient hypoxia common
  • RSV testing: not routinely recommended except for epidemiology, cohorting, or palivizumab recipients
  • Chest X-ray: variable findings; not routinely recommended
  • POCUS emerging as alternative diagnostic tool

Treatment

General Measures

  • Supportive care: nasal suctioning, hydration, oxygen if needed
  • Positive pressure ventilation (CPAP) for respiratory failure (limited evidence)
  • Avoid routine corticosteroids, bronchodilators, epinephrine (may be trialed selectively)
  • Parental education and support essential

Medications

  • Oxygen therapy if O2 saturation <90% (AAP recommends >90% if infant otherwise well)
  • Nebulized hypertonic saline (3%) may reduce hospital length of stay, but not recommended in ED
  • Antibiotics only if secondary bacterial infection suspected
  • High-flow nasal cannula widely used but unproven

Second-Line

  • IV or NG fluids if oral intake inadequate due to work of breathing

Additional Therapies

  • Ribavirin and palivizumab for high-risk prophylaxis per guidelines
  • Heliox therapy may have transient benefit in moderate/severe cases but no sustained effect
  • Trial of inhaled Ξ²-agonists in wheezing patients sometimes considered

Admission Criteria

  • Apnea or age <6 weeks (or <30 days)
  • Respiratory distress with RR >45/min, hypoxia (clinical context important)
  • Ill/toxic appearance
  • Underlying cardiac, respiratory, or immune conditions
  • Dehydration or feeding difficulty (<50% normal intake)
  • Uncertain home care environment

Discharge Criteria

  • Normal RR and no supplemental oxygen requirement
  • Home oxygen discharge possible with follow-up
  • Provide clear parental instructions for return precautions

Ongoing Care

Follow-Up

  • Monitor hospitalized patients based on severity
  • Home care: daily calls 2-4 days post-discharge, frequent outpatient visits as needed

Patient Education

  • Hand hygiene importance
  • Recognize signs of worsening respiratory distress

Prognosis

  • Recovery typically within 14-21 days; 40% symptomatic at 14 days, 10% at 4 weeks
  • Mortality <1%
  • High-risk infants (bronchopulmonary dysplasia, congenital heart disease) may have prolonged illness

Complications

  • Secondary bacterial infection
  • Bronchiolitis obliterans
  • Apnea
  • Respiratory failure
  • Death (rare)
  • Increased risk of later reactive airway disease (asthma)