BRONCHIOLITIS IN INFANTS AND CHILDREN R1 최원석

Definition for most clinical studies : First episode of wheezing in a child younger than 12 to 24 months who has physical findings of a viral respiratory infection and has no other explanation for the wheezing, such as pneumonia or atopy broader definition : Illness in children <2 years of age characterized by wheezing and airways obstruction due to primary infection or reinfection with a viral or bacterial pathogen, resulting in inflammation of the small airways/bronchioles

Typically caused by a viral infection. The proportion of disease caused by specific viruses varies depending upon the season and the year. Respiratory syncytial virus (RSV) is the most common cause Less common causes include parainfluenza virus, human metapneumovirus, influenza virus, adenovirus, rhinovirus, coronavirus, and human bocavirus

Respiratory syncytial virus(RSV) -Ubiquitous throughout the world and causes seasonal outbreaks. -In temperate climates, late fall and wintertime epidemics of bronchiolitis -In the southern hemisphere, wintertime epidemics occur from May to September, with a peak in May, June, or July

Typically affects infants younger than 2 years Peak incidence between 2 and 6 months of age and remains a significant cause of respiratory disease during the first 5 years of life Bronchiolitis is a leading cause of hospitalization in infants and young children Hospitalization for bronchiolitis occurs more frequently among boys than girls (62 vs 38 %) and in urban compared to rural settings

Risk factors for severe RSV disease and/or complications -Prematurity (gestational age <37 weeks) -Low birth weight -Age less than 6 to 12 weeks -Chronic pulmonary disease (bronchopulmonary dysplasia, cystic fibrosis, congenital anomaly) -Hemodynamically significant congenital heart disease (eg, moderate to severe pulmonary hypertension, cyanotic heart disease, or congenital heart disease that requires medication to control heart failure) -Immunodeficiency -Neurologic disease -Congenital or anatomical defects of the airways

Pathologic changes -Begin 18 to 24 hours after infection -Bronchiolar cell necrosis, ciliary disruption, and peribronchiolar lymphocytic infiltration -Edema, excessive mucus, and sloughed epithelial cells lead to obstruction of small airways and atelectasis

Viral upper respiratory prodrome followed by increased respiratory effort and wheezing Often preceded by a 1-3 day history of upper respiratory tract symptoms, such as nasal congestion and/or discharge and mild cough. It typically presents with fever (usually ≤38.3ºC), cough, and mild respiratory distress. Compared to other viruses causing bronchiolitis, fever tends to be lower with RSV and higher with adenovirus

Apnea may occur in infants, particularly in those born prematurely and those younger than 2 months of age Apnea is a risk factor for respiratory failure and the need for mechanical ventilation

Other aspects that help in determining the severity of illness and need for hospitalization include -Assessment of hydration status -Symptoms of respiratory distress (tachypnea, nasal flaring, retractions, grunting) -Cyanosis, indicating profound hypoxemia -Episodes of restlessness or lethargy (may indicate hypoxemia and/or impending respiratory failure)

Tachypnea and intercostal and subcostal retractions often with expiratory wheezing Chest may appear hyperexpanded with increased antero- posterior (AP) diameter and may be hyperresonant to percussion Auscultation include any combination of expiratory wheeze, prolonged expiratory phase, and both coarse and fine crackles Mild hypoxemia (SaO 2 <95 percent) commonly is detected by pulse oximetry

Severely affected patients have increased work of breathing with subcostal, intercostal, and supraclavicular retractions, nasal flaring, and expiratory grunting. They may appear cyanotic and have poor peripheral perfusion Wheezing may not be audible if the airways are profoundly narrowed. Other examination findings may include mild conjunctivitis, pharyngitis, and otitis media

Atelectasis Radiographic findings of atelectasis are common in bronchiolitis, particularly with RSV infection Otitis media Dehydration Comorbid serious bacterial infection Uncommon among infants and young children with bronchiolitis or RSV infection (meningitis, bacteremia, UTI, or bacterial enteritis)

American Academy of Pediatrics (AAP) defines severe disease as "signs and symptoms associated with poor feeding and respiratory distress characterized by tachypnea, nasal flaring, and hypoxemia" Patients with severe disease have a high likelihood of requiring intravenous hydration, supplemental O 2, and/or mechanical ventilation.

Factors associated with increased illness severity include -Toxic or ill appearance -SaO 2 <95 % by pulse oximetry while breathing room air -Age younger than 3 months -Respiratory rate ≥70 breaths per minute -Atelectasis on chest radiograph -Prematurity -Chronic pulmonary disease -Congenital heart disease -Chronic neurologic conditions -Immunodeficiencies

The duration of the illness depends upon the presence or absence of high-risk conditions such as prematurity or chronic lung disease, the severity of the illness, and the causative agent. Usually is a self-limited disease. In previously healthy infants who are older than 6 months and require hospitalization, the average length of hospitalization is 3 days The respiratory status typically improves over 2-5 days. However, wheezing persists in some infants for a week or longer

Although symptoms may persist for several weeks, the majority of children who do not require hospital admission return to their premorbid states by 28 days In children who do not improve at the expected rate, chest radiographs may be helpful in excluding other conditions in the differential diagnosis (eg, foreign body aspiration, heart failure..) Expected clinical course — The median duration of bronchiolitis for children younger than 24 months is 12 days. Approximately 20% of children remain ill after 3 weeks, and 10% still have symptoms after 4 weeks

Bronchiolitis is diagnosed clinically, based upon information from the history and physical examination Characteristic features include a viral upper respiratory prodrome followed by increased respiratory effort and wheezing in children younger than 2 years of age Radiographs and virologic tests support the diagnosis, but they are not routinely necessary to make the diagnosis

Viral-triggered asthma -History of recurrent wheezing episodes and a family or perso nal history of asthma, atopy -However during the first episode of wheezing, it is difficult to distinguish bronchiolitis from asthma Foreign body aspiration Pneumonia Gastroesophageal reflux disease Congenital heart disease

Therapy in most cases consists of supportive measures to ensure that the child is clinically stable, well hydrated, and well oxygenated. Respiratory support -AAP practice guideline recommends SaO 2 <90 % as the threshold to start supplemental oxygen -Infants with PaCO 2 >55 mmHg, hypoxemia despite O 2 supplem entation, and/or apnea may require mechanical ventilation Fluid administration

Chest physiotherapy -Using vibration and percussion did not improve clinical score, reduce supplemental O 2 requirement, or reduce length of hospital stay. -Use of chest physiotherapy is discouraged because it may increase the distress and irritability of ill infants.

Inhaled bronchodilators -Suggest a trial of inhaled bronchodilators for children with bro nchiolitis (Grade 2B). -The bronchodilator response should be objectively assessed before and up to one hour after treatment. -If clinical response, aerosolized bronchodilator therapy can b e administered every 4-6 hours and discontinued when the si gns and symptoms of respiratory distress improve Recommend not using oral bronchodilators in the management of bronchiolitis

Inhaled bronchodilators - Albuterol 0.15 mg/kg (minimum 2.5 mg; maximum 5 mg) diluted in 2.5 to 3 mL saline and administered over 5 to 15 min ; or 4 to 6 puffs via a metered dose inhaler with spacer and facemask. -If no benefit is observed in 1 hour, administer a single dose of nebulized epinephrine -Epinephrine ( 0.05 mL/kg of 2.25 % epinephrine diluted in 3 mL normal saline). -If no clinical response is seen within 1hour of epinephrine treatment, do not continue the use of these agents. -If there is a response to either albuterol or epinephrine, bronchodilator ther apy can be administered every 4-6 hours and discontinued when the signs and symptoms of respiratory distress improve.

Systemic glucocorticoids -Recommend not using glucocorticoids routinely in the treatm ent of previously healthy infants hospitalized with a first epis ode of bronchiolitis (Grade 1A). -However, glucocorticoids may be beneficial in infants with chronic lung disease (bronchopulmonary dysplasia) and thos e with recurrent episodes of wheezing suggestive of asthma. -Prednisolone or prednisone (1 to 2 mg/kg per day in one dose or divide d into two doses per day for 3-7days). - An alternative is dexamethasone (0.4 mg/kg per day in one dose for 3 to 5 days).

Ribavirin -Recommend not using ribavirin routinely in the treatment of p reviously healthy children with bronchiolitis (Grade 1B) Antibiotics -warranted only when there are specific indications of a coexisting bacterial infection

Discharge criteria -Respiratory rate <70 /min -Caretaker can clear the infant's airway using bulb suctioning -Patient is stable without supplemental O 2 -Patient has adequate oral intake to prevent dehydration -Caretaker is confident they can provide care at home -Education of the family is complete