Esther M. Sampayo
Each epidemic season, the emergency physician is faced with evaluating, treating, and determining the disposition of infants and young children with bronchiolitis. The American Academy of Pediatrics defines bronchiolitis as “rhinitis, tachypnea, wheezing, cough, crackles, use of accessory muscles, and/or nasal flaring in a child less than 24 months” (3). Unlike children with reactive airway disease, the lower respiratory tract symptoms of children with bronchiolitis are caused by an acute infection causing inflammation of the bronchiolar epithelium. The resultant necrosis of epithelium causes plugging of the smaller airways by cellular debris, resulting in air trapping or atelectasis distal to the obstruction. This results in tachypnea, wheezing, rales, increased work of breathing, and potentially hypoxemia.
Respiratory syncytial virus (RSV) is probably the most important respiratory pathogen in young children and may cause serious morbidity and even mortality. It is the leading cause of infant hospitalization. While the overall hospitalization rates for bronchiolitis have dropped by 17% over the last decade, the number of cases in children with high-risk medical conditions (e.g., prematurity) increased by 34%, and the rate of mechanical ventilation increased by 21% (11,20). More than 50% of infants will acquire RSV infection during their first epidemic season, and 40% of these will progress from upper to lower respiratory tract illness. Three percent of all children <1 year of age will require hospital admission for bronchiolitis (20). The peak incidence of lower airway disease occurs in infants 2 to 5 months of age (9,20). The mean annual mortality rate is estimated to be 2.8 per 100,000 births, with almost 80% of deaths occurring in patients younger than 12 months old.
Children in high-risk groups are at greatest risk for severe disease and death and require monthly immunoprophylaxis with palivizumab or RSV immunoglobulin during the RSV season. These include (1) those in the first few months of life with a history of prematurity (≤35 weeks’ gestational age), (2) those with congenital heart disease (CHD), (especially uncorrected pulmonary hypertension), (3) those who are immunosuppressed, and (4) those with chronic lung disease (CLD) (11,12). Environmental risk factors such as passive smoking, crowded households, and attendance at day care may contribute independently to disease severity.
There are two major subtypes of the RSV virus, strains A and B. Subtype A is commonly associated with more severe disease. Although RSV is the most common pathogen, other viruses, including parainfluenza type III, influenza, adenovirus, rhinoviruses, and mycoplasma, can also cause bronchiolitis (9). Human metapneumovirus (hMPV) is a newly described paramyxovirus associated with upper and lower respiratory tract symptoms similar to RSV bronchiolitis and is responsible for 5% to 10% of hospitalizations (24). Bronchiolitis caused by hMPV is usually found in older infants and is associated with a higher incidence of fever and atelectasis.
CLINICAL PRESENTATION
The presentation of the infant or young child with bronchiolitis ranges from the smiling, interactive child with mild tachypnea and end-expiratory wheezing to the child who presents with impending respiratory failure. Typically, there is a 3- to 5-day history of upper respiratory tract symptoms, including coryza and congestion, before the onset of lower respiratory tract symptoms. The parent may have noted that the child developed a “cold,” is not as active, is breathing faster, or has difficulty feeding. Although most patients have tachypnea, cough, wheezing, and increased work of breathing, the infant under 3 months may simply present with lethargy, irritability, or apnea and have few to no lower respiratory findings. Fever is often present early in the course of illness, but may be absent or low grade at the time lower respiratory tract symptoms develop. Lower respiratory tract involvement usually peaks within 3 to 5 days. Resolution of symptoms overall, including cough, wheezing, and mild hypoxemia, however, may take days to weeks.
DIFFERENTIAL DIAGNOSIS
Emergency physicians must be careful not to anchor on the diagnosis of bronchiolitis in infants during epidemic winter months and should consider other causes of lower respiratory tract illness. While bronchiolitis is a clinical diagnosis, children with atypical presentations, such as severe respiratory distress or absence of viral symptoms, may require more extensive diagnostic evaluation to investigate potential other causes. Congenital heart disease (CHD) and congestive heart failure are initially thought to be bronchiolitis, given that infants may present with symptoms very similar to those of bronchiolitis including poor feeding, tachypnea, rales, and wheezing. Congenital airway lesions, such as vascular rings, slings, teratomas, or bronchogenic cysts, may also present with symptoms suggestive of bronchiolitis. Aspiration from gastroesophageal reflux or tracheoesophageal “H-type” fistulas can cause symptoms precipitated by feeding that may mimic bronchiolitis. Other diagnostic considerations include congenital infections such as chlamydial or community-acquired pneumonia, foreign body aspiration, and allergic reactions. Recurrent symptoms should lead to consideration of cystic fibrosis, immunodeficiency, or asthma. It is often difficult to distinguish bronchiolitis from asthma (reactive airway disease) in older infants and children. However, the first episode of wheezing with upper respiratory tract symptoms in the young child should be considered to be bronchiolitis. Children with atopy, prior episodes of wheezing responsive to bronchodilator therapy, and a strong family history of asthma may indeed have asthma or be at increased risk of asthma (23). Children who have wheezing beyond 12 months of age, are atopic, or have eosinophilia may be at increased risk of developing asthma as well (23). It is unclear whether children who develop lower respiratory tract illness have a predisposition to reactive airway disease or whether the viral infection itself causes pulmonary damage or immunologic changes leading to the development of asthma. On the other hand, repeated episodes of bronchiolitis are not uncommon, and infants who have had RSV bronchiolitis may be more prone to repeated episodes in the first year of life independent of their baseline risk for asthma. Therefore, in the absence of a strong family history, repeated wheezing episodes during the first year of life should be attributed to bronchiolitis and not asthma.
ED EVALUATION
No single fact or finding during emergency department (ED) evaluation is sensitive enough to predict which child will develop severe disease. A combination of history and physical examination findings is crucial in assessing any patient’s risk for significant morbidity (Table 264.1). The history must include the gestational age at birth and whether there were any perinatal complications, such as CLD (formerly called bronchopulmonary dysplasia). As mentioned previously, underlying diseases or anomalies such as CHD, cystic fibrosis, or immunodeficiency, may also put the infant at increased risk. It is vital to determine whether the child is in the first few days of illness, in which case the disease may continue to progress and become more severe, or beyond the 3- to 5-day peak which marks the beginning of the convalescent stages of the illness. Social issues must also be considered as part of risk stratification, including the mother’s ability to care for a sick infant or to return for additional care if the disease progresses.
TABLE 264.1
Risk Factors Associated with More Severe Disease
The child’s overall appearance is a sensitive indicator of disease severity. It is important to evaluate the respiratory rate, accessory muscle use for breathing, air exchange, and hydration status at presentation and after therapeutic trials. The oxygen saturation, as determined by pulse oximetry, is the single most objective predictor of more severe disease and should be measured on all infants and children presenting to the ED with bronchiolitis. Hydration status, as determined by physical examination (moistness of mucous membranes, capillary refill at the fingertip, presence or absence of tears), is crucial to assess since bronchiolitis-associated tachypnea accelerates insensible fluid losses and inhibits oral intake, sometimes leading to significant dehydration. Level of hydration as well as respiratory status play an important role in determining patient disposition.
Radiographs are not routinely indicated in infants or young children with bronchiolitis unless an alternative diagnosis is suspected or when there is severe disease. The majority of routine bronchiolitis radiographs show some degree of hyperaeration or peribronchial thickening (19). Infiltrates occur in <10% of children presenting for outpatient evaluation; the risk of airspace disease appears to be greater in children with oxygen saturation <92% or severe distress. There is limited and controversial evidence that atelectasis on a chest x-ray correlates with progression to severe disease. More importantly, though, routine radiography may actually increase unnecessary use of antibiotics when atelectasis is misinterpreted as an infiltrate (19,25).
Evaluation of fever in infants younger than 2 or 3 months of age should be performed as per usual practice (see Chapter 222). Although the rate of bacteremia is low in infants with bronchiolitis, it may still occur in about 1% of RSV-positive infants. Furthermore, the risk of urinary tract infection is reduced in RSV-positive infants, but is still common enough to require screening (15). For infants older than 2 months of age with classic bronchiolitis, fever is unlikely to indicate serious bacterial illness and is more likely to be due to early viral illness, pneumonia, or otitis media (4,13,25). Therefore, routine culture of the blood or urine may be unnecessary. Complete blood cell counts are rarely useful and are weak screening tools. Microbiologic testing to determine viral etiology is indicated only for those with, or at significant risk of, severe disease (CLD, CHD) or for the purposes of infection control and isolation.
KEY TESTING
• Bronchiolitis is a clinical diagnosis based on history and physical examination findings. Chest radiography, blood tests, and viral testing are not routinely recommended for ED patients.
ED MANAGEMENT
To date, there is no strong evidence supporting the effectiveness of any single treatment for bronchiolitis (1,3,25). Most children presenting with bronchiolitis have mild or moderate severity of disease. Those with mild disease require only supportive therapy, which includes maintenance of hydration and respiratory support. Intravenous fluids may be required because of insensible losses due to respiratory distress, combined with poor oral intake. Normal saline boluses of 20 mL/kg and additional maintenance fluid may be required for those with signs of dehydration such as tachycardia, sunken fontanel, and prolonged capillary refill. Oxygen supplementation is indicated if the patient’s SpO2 level is consistently below 90% or if the patient is in severe distress despite an adequate SpO2. Suctioning may be helpful, but there is no evidence for the benefit of deep suctioning (3). There is some suggestion in the literature that nebulized 3% normal saline may be beneficial in breaking up secretions (14,25). The role of heliox in the management of bronchiolitis remains uncertain (3). Chest physiotherapy is not recommended.
The use of bronchodilators such as nebulized albuterol for bronchiolitis is controversial. (1,3,8). Clinical practice guidelines recommend that bronchodilators not be used routinely in the management of bronchiolitis. Although bronchodilators produce small short-term improvements in clinical scores, this must be weighed against the costs and adverse effects of these agents. Infants and children with bronchiolitis may undergo a trial of an inhaled bronchodilator, however—albuterol 0.15 mg/kg via nebulizer or 4 to 6 puffs via MDI with spacer and facemask. The effects should be assessed within 1 hour for objective improvement in oxygen saturation, lowering of the respiratory rate, or improved aeration. For those who do not improve, there is no need to continue further treatments (3). Nebulized racemic epinephrine has been considered more effective than β2-agonists in several clinical trials and may be tried for those who do not respond to albuterol and will require hospitalization, but a number of recent studies do not support the routine use of epinephrine (3,8,10,21,25). A trial dose of 0.05 mL/kg of 2.25% epinephrine is an option for children who do not respond to albuterol, but treatment should not be continued in the absence of a clinical response within 1 hour.
Oral corticosteroids are not recommended in the treatment of bronchiolitis since there is no consistent evidence supporting their use (1,3,5–7,17,18,25). However, corticosteroids may provide some benefit in combination with racemic epinephrine and this suggests there may be a future role for them in combination with other therapies (17,25). Steroids should be considered for children with multiple episodes of wheezing responsive to bronchodilator therapy, those with atopy, and those with a strong family history of asthma. Antibiotics are indicated only when a bacterial infection has been diagnosed, or for febrile neonates. Of note, more than 60% of children with bronchiolitis develop bacterial ear infections (4). Inhaled corticosteroids montelukast, cromolyn sodium, ribavirin, and immunoglobulins have all shown little evidence of clinical efficacy for bronchiolitis and are not recommended.
Children with moderate or severe respiratory distress should be allowed to assume a position of comfort, and 100% oxygen should be delivered. Suctioning of copious nasopharyngeal secretions may relieve some distress caused by airway obstruction. A trial of bronchodilators and/or racemic epinephrine should be delivered. Heated humidified oxygen administered by high-flow nasal cannula or nasal continuous positive airway pressure may be effective in preventing intubation and mechanical ventilation in severe cases of bronchiolitis (16). However, additional studies are necessary to determine what role these modalities should play in the management of severe bronchiolitis. Intubation is required for the child with severe respiratory distress or failure to respond to these measures.
CRITICAL INTERVENTIONS
• Use pulse oximetry to identify children with hypoxemia. This is the most specific and objective indicator of more severe disease. Cyanosis detectable on physical examination does not occur until the oxygen saturation is <85%!
• Beware of dehydration, as infants with respiratory distress and copious secretions are at risk for poor feeding and have increased water losses due to fever and increased work of breathing.
• Suction the infant to help improve airway obstruction.
• Keep the infant in the position of comfort as long as possible and avoid agitating the patient.
DISPOSITION
Most infants and children with bronchiolitis do not require admission. Clearly, those in respiratory distress or with hypoxia or dehydration require intervention and admission. Among those with mild or moderate disease, no single factor can predict the need for admission (1,3,25). Children at high risk for developing more severe disease (see Table 264.1) should be considered for admission or close outpatient observation. Hospitalization should be strongly considered for infants at risk for apnea: premature infants younger than 37 weeks and <48 weeks after conception, full-term infants younger than 1 month of age, and infants with a prior apnea episode witnessed either by the family or the practitioner (23). Children who are early in the course of the illness or have moderate severity of illness that does not require admission should have follow-up arranged in 24 hours. Criteria for discharge include the following:
• No signs of severe respiratory distress.
• Caretaker is comfortable using bulb suctioning.
• Patient does not require supplemental oxygen.
• Patient’s oral intake is adequate to prevent dehydration.
• Caretaker is comfortable and has resources available to take care of patient at home.
• Anticipatory guidance has been reviewed.
• Close primary care follow-up can be achieved.
Children with underlying medical conditions should have their subspecialist physicians consulted about treatment and indications for admission. For example, the pediatric cardiologist can determine whether the child with CHD has significant uncorrected pathology that creates a higher risk of deterioration. If the diagnosis of bronchiolitis is not clear, a pediatrician may offer further help with the differential diagnosis or workup.
Children with respiratory failure requiring intubation should be transferred to a facility with a pediatric intensive care unit. Children with underlying medical conditions or at high risk for severe disease or mortality should also be transferred to a facility with pediatric subspecialists and a pediatric intensive care unit.
Common Pitfalls
• Failure to identify that the child is in the first few days of illness and may become progressively worse. Children who appear to have mild illness may progress over the next hours or days and thus require close outpatient follow-up. The caregiver should be given specific instructions of what to look for and when to return.
• Failure to assess the child’s hydration status and to treat with intravenous fluid when indicated.
• Failure to identify the child with an underlying condition or a history of prematurity that put him or her at high risk for morbidity and mortality.
• Persistence in using bronchodilators despite no evidence of response. Less than 50% of infants with bronchiolitis respond to bronchodilators. If they have mild disease, they should be sent home with symptomatic care instructions and follow-up arrangements.
• Overuse of routine laboratory tests or radiographs in the infant or young child with bronchiolitis. Testing should be tailored to the individual patient.
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