Definition- Bronchiolitis is a clinical syndrome of infection and associated inflammation of the lower respiratory tract that generally occurs in children less than 2 years of age. It is usually associated with a viral pathogen and can be associated with wheezing and/or rales.
Pathophysiology- Viral infection of terminal bronchiolar epithelial cells
- Edema, mucus formation, sloughing of epithelial cells with subsequent obstruction of small airways and atelectasis
- Most common cause is RSV (late fall/winter), followed by rhinovirus (spring/fall). Other causes include human metapneumovirus, influenza, adenovirus, and coronavirus. Approximately 1/3 of patients have infection with 2 or more viruses.1
Risk factors for Severe Disease- Chronic pulmonary disease
- Congenital/anatomic defects of the airways
Clinical Features- URI symptoms with presentation typically at day 3-6
- Peak symptoms thought to occur ~day 4-7
- Tachypnea, retractions, wheezing, rales, mild hypoxemia
- Hyperexpanded on chest x-ray
- Comorbid serious infections low (1-2% for bacteremia/meningitis, 5% for UTI) although in intubated infants, frequency of bacterial superinfection is as high as 40%)2,3
- Apnea ~5% incidence (younger age, prematurity, increased risk of respiratory failure)
- Respiratory failure in about 15%
Figure 1. Peribronchial Cuffing Typical of Bronchiolitis (occlusion of small airways via mucus plugging leads to atelectasis and prominent appearance of bronchioles). Another common finding is shifting atelectasis.
Treatment- Fluid hydration (ADH levels may be elevated so consider isotonic fluids)
- Supplemental O2 to maintain SpO2 >90-92% (AAP guidelines of >90% although no specific data).
- In a multicenter randomized trial of infants <12 months of age with bronchiolitis treated outside of an ICU, those who received high flow nasal cannula at 2 L/kg/min (avg weight ~ 7.3-7.6 kg) had significant less treatment failure than those who were started on regular nasal cannula at 2L/min. 61% of those that failed nasal cannula responded to HFNC (Franklin et al, NEJM 2018)
- Chest PT did not improve respiratory parameters, O2 requirement, or length of stay in non-intubated patients4
- Trial of inhaled bronchodilators (albuterol) -maybe- if strong personal or family history of reactive airway disease, if no response, stop
- Hypertonic saline: Some evidence to suggest decreased risk of hospitalization and length of stay in hospitalized patients (newer RCT evidence-Angoulvant, JAMA PEDS 2017- did not show such an improvement in admission rates)5
- Steroids generally NOT recommended unless clear history of previous reactive airway disease
- Ribavarin generally not recommended unless immunocompromised or severe disease
- RSV-IVIG and RSV-monoclonal Ab not recommended as no effect on outcomes
- Possible reduced duration of mechanical ventilation with surfactant although not routinely used6
- No significant evidence to support the use of heliox
The Bottom Line: - Supportive care with HFNC/CPAP/Mechanical ventilation as needed
- Antibiotics, guided by tracheal aspirate in the intubated population (in general, given ~40% risk of coinfection and associated decrease in mechanical ventilation/length of stay3,7)
- Suctioning and PT not particularly helpful in the general inpatient population but may be necessary in the PICU population
- Trial of albuterol, maybe...
- Hypertonic saline frequently utilized (ie q6hrs with albuterol given propensity of HTS to produce bronchospasm) but newer evidence suggests likely no benefit
- Tincture of time- length of mechanical ventilation and PICU stay can be quite variable
Complications- Possible association with the development of asthma but unclear
- Mortality <2% in developed world
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