Bronchiolitis

Girish D. Sharma, MD, FCCP

Introduction/Etiology/Epidemiology

•Bronchiolitis is a lower respiratory tract viral infection in infants, characterized by acute inflammation, edema, necrosis of the epithelial lining of the small airways, and mucus production.

•Bronchiolitis is the most common cause of hospital admission among infants during the first 12 months of life.

•In the United States, 2%–3% of infants younger than 12 months are hospitalized with a diagnosis of bronchiolitis.

•Bronchiolitis is most commonly caused by respiratory syncytial virus (RSV) (50%–80%), followed by human rhinovirus (5%–25%), parainfluenza, human metapneumovirus, coronavirus, adenovirus, influenza, and enterovirus.

•Bronchiolitis occurs most commonly from November to March in the United States, with some regional variation; human rhinovirus RSV occurs most commonly in the spring and fall.

•Ninety percent of children are infected with RSV in the first 2 years of life; ≤40% have signs and symptoms of lower respiratory tract infection during the initial infection.

Clinical Features

•In a typical case, after an incubation period of 4–6 days (range, 2–8 days), upper respiratory infection symptoms develop with irritability and poor feeding.

•Bronchiolitis typically begins as an upper respiratory infection with rhinorrhea, congestion, and cough, which may progress to tachypnea, grunting, wheeze, inspiratory crackles, rales, use of accessory muscles with retractions, and nasal flaring.

•Patients with more severe disease and respiratory distress may develop feeding with interruptions, reduced oral intake, dehydration, apnea, and respiratory failure.

•Risk factors include age <12 weeks, history of prematurity, underlying cardiopulmonary disease, immunodeficiency, and low concentration of maternal antibodies.

•Babies with low ex vivo interferon-γ responses in early life are more likely to have frequent viral respiratory infections, including those associated with wheeze.

•Bronchiolitis is likely to be more severe in the presence of chronic lung disease of prematurity, in infants born before 29 weeks, and in the presence of certain types of hemodynamically important congenital heart disease with pulmonary hypertension or congestive heart failure. Other factors include chronic lung disease caused by cystic fibrosis and Down syndrome and perinatal environmental smoke exposure.

•Twenty-five percent to 50% of patients who receive a diagnosis of bronchiolitis have similar recurrent symptoms, in the form of viral infection–associated wheeze.

•RSV bronchiolitis has been correlated with subsequent development of wheeze and asthma, and recent findings from the “COAST” (Childhood Origins of Asthma) study suggest that early rhinovirus illnesses are a more robust predictor of subsequent development of asthma in high-risk children.

Diagnostic Considerations

•American Academy of Pediatrics (AAP) clinical practice guidelines indicate that physicians should diagnose bronchiolitis and assess the disease severity on the basis of history and physical examination findings.

•The guidelines do not advocate the use of radiographic or laboratory studies routinely.

•Antigen testing of nasal washings, respiratory viral panel, and viral cultures is not routinely recommended.

Management

•Supportive management consists of oxygen supplementation when oxygen saturation at pulse oximetry (SpO₂) is <90%, with intravenous or nasogastric fluids administered to children with inadequate oral intake.

•AAP clinical practice guidelines do not recommend the administration of nebulized hypertonic saline in the emergency department or the administration of albuterol, epinephrine, or systemic steroids.

•Use of continuous pulse oximetry, chest physical therapy, and antibiotics (unless there is concomitant bacterial infection or strong suspicion) is not recommended by AAP guidelines.

•The physician may choose not to administer oxygen supplementation if the oxyhemoglobin saturation exceeds 90%.

Prevention

•Palivizumab should be given during the first year of life to infants with hemodynamically significant heart disease, chronic lung disease, or prematurity (preterm infants <32 weeks’ gestation who require >21% oxygen for at least the first 28 days after birth).

•A maximum of 5 monthly doses (15 mg/kg per dose) should be given during the RSV season for the infants that qualify for its administration.

•Use alcohol-based disinfectant hand rubs or perform thorough handwashing with soap and water before and after direct contact with the patient, after contact with inanimate objects in the direct vicinity of the patient, and after removing gloves.

•Counsel parents about the harmful effects of tobacco smoke exposure and advise smoking cessation.

•Encourage breastfeeding.

•Educate medical personnel and family members on appropriate evidence-based diagnosis, treatment, and prevention of bronchiolitis.

Prognosis

•The prognosis is usually self-limited, with a high degree of morbidity and a low mortality rate.

•Up to 60% of patients may develop acute otitis media.

•The presence of apnea, respiratory distress, respiratory failure, poor oral intake and resultant dehydration, and inability of the caretaker to monitor the infant may warrant hospitalization.

•Reported rare complications include myocarditis, arrhythmia, complete heart block, sepsis-like syndrome, seizures, focal neurological deficits, and hepatitis.

•Some patients develop asthma subsequent to human rhinovirus bronchiolitis.

•The mortality rate is ≤2.0 per 100,000 live births, with most deaths occurring in the 1–3-month-old age group; risk factors are low birth weight, increasing birth order, low 5-minute Apgar score, young maternal age, unmarried mother, and tobacco use during pregnancy.

•For patients with RSV bronchiolitis who are admitted to the pediatric intensive care unit, a mortality rate of 2%–7% has been reported.

•Reported long-term sequelae after severe bronchiolitis include bronchiolitis obliterans, allergic sensitization, wheeze, and asthma.

When to Refer

•Poor oral intake; dehydration; low oxyhemoglobin saturation (SpO₂ <90%); inability of the caretaker to monitor the patient; presence of complications, such as marked respiratory distress and apnea; and signs of respiratory failure are indications for referral.

•The presence of risk factors for severe disease, such as age <12 weeks, history of prematurity, underlying cardiopulmonary disease, or immunodeficiency, are indications for referral.

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