Episode 33 – Acute Bronchiolitis: Assessment and Management in the Emergency Department (Pharmacology CME)

Pathophysiology

• Bronchiolar narrowing and obstruction is caused by:
  • Increased mucus secretion
  • Cell death and sloughing
  • Peri-bronchiolar lymphocytic infiltrate
  • Submucosal edema
• Smooth muscle constriction seems to have a limited role, perhaps explaining the lack of response to bronchodilators.
• Median duration of illness is 12 days in children <24 months
• 18% still ill at 3 weeks.²
• 9% still ill at 4 weeks.²

Etiology

• RSV accounts for 50-80% of cases, but rare in children >2 yo.³
  • Late fall epidemic peaking Nov-March, in the US.⁴
• Human Metapneumovirus (HMPV) accounts for 3-19% ^5,6
  • Similar seasonal variation to RSV.
• Parainfluenza, influenza, adenoviruses, coronaviruses, rhinoviruses, and enteroviruses are other causes.^4-6
• Rhinoviruses have been shown to play a larger role in Asthma.⁷

Presentation

• The American Academy of Pediatrics defines it as any of the following in infants: ¹
  • Rhinitis
  • Tachypnea
  • Wheezing
  • Cough
  • Crackles
  • Use of accessory muscles
  • Nasal flaring

Differential Diagnosis

• Emergent Causes
  • Infection: pneumonia, chlamydia, pertussis
  • Foreign body: aspirated or esophageal
  • Cardiac anomaly: congestive heart failure, vascular ring
  • Allergic reaction
  • Bronchopulmonary dysplasia exacerbation
• Non-acute Causes
  • Congenital anomaly: tracheoesophageal fistula, bronchogenic cyst, laryngotracheomalacia
  • Gastroesophageal reflux disease
  • Mediastinal mass
  • Cystic fibrosis
• Clinical Pearls
  • Vomiting, wheezing, and coughing associated with feeding; consider GERD.
  • Wheezing associated with position changes; consider tracheomalacia or great vessel anomalies.
  • Wheezing exacerbated by flexion of neck and relieved by neck hyperextension; consider vascular ring.
  • Multiple respiratory tract infections and failure to thrive; consider cystic fibrosis or immunodeficiency.
  • Wheezing with heart murmur, cardiomegaly, cyanosis, exertion or sweating with feeding; consider cardiac disease.
  • Sudden onset of wheezing and choking; consider foreign body.

Risk Factors for Severe Bronchiolitis

• Age < 6-12 weeks^11-13
• Prematurity < 35-37 weeks’ gestation^11-13
• Underlying respiratory illness such as bronchopulmonary dysplasia¹
• Significant congenital heart disease; immune deficiency including HIV, organ or bone marrow transplants, or congenital immune deficiencies^14,15
• Altered mental status (impending respiratory failure)
• Dehydration due to inability to tolerate oral fluids
• Ill appearance¹²
• Oxygen saturation level ≤ 90%¹
• Respiratory rate: > 70 breaths/min or higher than normal rate for patient age^1,12
• Increased work of breathing: moderate to severe retractions and/or accessory muscle use1
• Nasal flaring
• Grunting

Risk Factors for Apnea

• Full-term birth and < 1 month of age^16,17
• Preterm birth (< 37 weeks’ gestation) and age < 2 months post birth^11-13,17
• History of apnea of prematurity
• Emergency department presentation with apnea¹⁷
• Apnea witnessed by a caregiver¹⁷

Diagnostic Testing

• Xray
  • Radiographs increase the likely hood of a physician giving antibiotics, even if the X-ray is negative.^18-20
  • Routine radiography is discouraged, but may be helpful when severe disease requires further evaluation or exclusion of foreign body.
• Viral testing is not necessary for the diagnosis but may help when searching for the cause of fever in young infants.
  • 2016 ACEP fever guidelines note that positive viral testing can impact further workup of fever for a serious bacterial infection (SBI).²¹
• In infants <28 days, serious bacterial infection is high, even in patients with bronchiolitis: 10% (RSV+) and 14% (RSV -)²². Standard fever evaluation is recommended.
• In the 28-60 day old group, SBI rates were 5.5% (RSV+) and 11.7% (RSV-). All were UTIs.²² Urinalysis is recommended.

Emergency Department Treatment

• Oxygen
  • Keep O2 saturation >90%
  • Clinicians may choose not to use continuous pulse oximetry (weak recommendation due to low-level evidence and reasoning)¹
• Fluids
  • IV or NG administration of fluids to combat dehydration, until respiratory distress and tachypnea resolve.
• Suctioning
  • Routine use of “deep” suctioning may not be beneficial and may be harmful.¹
  • Nasal suction should be used to help infants with respiratory distress, poor feeding or sleeping.
• Bronchodilators^1,25,26
  • Generally nor recommended for routine use.
  • May trial in infants with:
  • Severe bronchiolitis (these were excluded in the studies).
  • History of prior wheezing.
  • Family history of atopy/asthma in an older infant.
• Anticholinergic Agents (ipratropium bromide)
  • No evidence for improvement in bronchiolitis.^31-34
• Corticosteroids
  • AAP¹, Cochrane Review²⁷, and PECARN²⁸ study all recommend against, finding no evidence for improvement.
  • One small study (70 patients) found a benefit utilising 1 mg/kg oral dexamethasone followed by 0.6 mg/kg daily for 5 days. However, the study limited by size and increased prevalence of family history of atopy.
  • Recommendations remain against use in first time wheezers with bronchiolitis.
• Racemic Epinephrine
  • Not recommended¹. Further study needed.
• Racemic Epinephrine + Oral Dexamethasone
  • Pediatric Emergency Research Canada trial at 8 Canadian pediatric EDs involving 800 infants aged 6 weeks to 12 months with bronchiolitis found that the epinephrine-dexamethasone group had a lower admission rate over 7 days than the placebo group (17.1% vs 26.4%). This was not statistically significant. Further study needed. ³⁰
• Hypertonic Saline
  • AAP guidelines do not recommend use in the ED but note clinicians may utilize it in the inpatient setting. ¹
  • Cochrane reviews in 2013 and 2017 found some inpatient benefit, but a conflicting publication found it may worsen cough.^35-37
• High Flow Nasal Cannula (HFNC)
  • Several small pediatric ICU studies show a benefit in severe cases. No large ED randomized trials exist, to date.
  • Study protocols included weight based or age based flow rates.
• Nasal CPAP
  • Shows benefit in pediatric ICU settings. Evidence vs HFNC is limited.

Disposition

• Consider admission if any of the following are present:
  • Risk for apnea
  • Risk for severe bronchiolitis
  • Respiratory distress, particularly if it interferes with feeding
  • Hypoxia (oxygen saturation ≤ 90%)
  • Decreased feeding and/or dehydration
  • An unreliable caregiver (ie, unable to ensure patient care and appropriate 24-hour follow-up)
• All patients with severe bronchiolitis should be admitted.