Residency · Residency · Emergency Medicine

Pediatric Respiratory Emergencies: Croup, Bronchiolitis, and Pneumonia

Croup (Laryngotracheobronchitis)

Epidemiology and Pathophysiology

Croup is the most common cause of upper airway obstruction in children between 6 months and 3 years of age, with peak incidence at 1 to 2 years. It is rare after age 6 because the airway is larger. The most common cause is parainfluenza virus types 1 and 3, which account for about 75 percent of cases, with RSV, influenza, adenovirus, and rhinovirus responsible for the rest. The pathology involves subglottic edema that narrows the airway, and children are particularly vulnerable because of their small airway diameter and compliant cartilage. Croup occurs seasonally, predominantly in fall and early winter.

Clinical Presentation

A URI prodrome of 1 to 2 days with rhinorrhea and low-grade fever precedes the classic triad of a barky, seal-like cough, inspiratory stridor, and hoarseness. Symptoms are characteristically worse at night, typically peak on day 2 to 3, and resolve by day 5 to 7. The Westley Croup Score assesses severity: mild croup features a barky cough without stridor at rest and without retractions; moderate croup includes stridor at rest with mild retractions but no agitation; severe croup presents with severe stridor, significant retractions, agitation, and potentially cyanosis.

Imaging

Imaging is not routinely necessary because the diagnosis is clinical. An AP neck X-ray may show the "steeple sign" of subglottic narrowing, but this finding is neither sensitive nor specific, and treatment should not be delayed for imaging.

Management

Dexamethasone is the mainstay of treatment for all severity levels. A single dose of 0.6 mg/kg is given orally or intramuscularly (maximum 16 mg). Onset is 2 to 3 hours for the oral route, with full effect at 6 hours. It reduces ED return visits and hospitalization. Even mild croup benefits from a single dose. Oral and intramuscular routes are equally effective, with oral preferred because it is less invasive. Lower doses of 0.15 mg/kg may be equally effective for mild croup, but 0.6 mg/kg remains the standard.

Nebulized racemic epinephrine (0.5 mL of 2.25 percent solution in 3 mL normal saline) is used for moderate to severe croup. Its onset is 10 to 30 minutes with a duration of 1 to 2 hours. Patients must be observed for 2 to 4 hours after administration for rebound, which is the return of symptoms after the epinephrine wears off. If a second dose is needed, admission should be strongly considered. L-epinephrine (1:1000) at 5 mL nebulized is an alternative if racemic epinephrine is not available.

Heliox, a helium-oxygen mixture, can be used for severe croup unresponsive to the above measures by reducing turbulent airflow. Intubation is rarely needed, and when required, a tube 0.5 to 1 size smaller than predicted should be used.

Disposition

Mild croup that has received dexamethasone and has no stridor at rest can be discharged with return precautions. Moderate croup that required epinephrine should be observed for 2 to 4 hours, and if no rebound occurs, the patient may be discharged. Severe croup, cases requiring multiple epinephrine doses, or a toxic appearance warrant admission.

Differential Diagnosis

Bacterial tracheitis presents with a toxic appearance, high fever, and poor response to standard croup treatment. It often follows viral croup and requires antibiotics and possible airway intervention. Epiglottitis, which is rare since the Hib vaccination, has a sudden onset with drooling, tripod positioning, a muffled "hot potato" voice, and no barky cough. The differential also includes peritonsillar or retropharyngeal abscess and foreign body aspiration.

Bronchiolitis

Epidemiology and Pathophysiology

Bronchiolitis is the most common lower respiratory infection in infants under 12 months, with peak incidence at 2 to 6 months and most hospitalizations occurring in infants under 6 months. RSV is the most common cause (50 to 80 percent), followed by rhinovirus, metapneumovirus, parainfluenza, and adenovirus. The pathology involves inflammation, edema, and necrosis of the small airway epithelium, leading to mucus plugging, air trapping, and atelectasis. It is a seasonal illness, occurring primarily from November through March in the Northern Hemisphere.

Clinical Presentation

A URI prodrome of 2 to 3 days with rhinorrhea, cough, and low-grade fever is followed by progressive tachypnea, wheezing, crackles, retractions, nasal flaring, and grunting. Apnea is particularly concerning in infants under 2 months, premature infants, and those with a history of apnea. Peak severity occurs on days 3 to 5, with resolution over 1 to 3 weeks, though cough may persist. Feeding difficulty due to respiratory distress is a common reason for admission.

Diagnosis

Bronchiolitis is a clinical diagnosis, and routine testing is not recommended by the AAP. RSV testing is not routinely needed because it does not change management, though it may be useful for cohorting hospitalized patients. Chest X-ray is not routinely indicated because it frequently shows hyperinflation and patchy atelectasis, findings that are often misinterpreted as pneumonia and lead to unnecessary antibiotics. Blood work is not routinely indicated.

Management — What Works

Supportive care is the cornerstone: nasal suctioning, adequate hydration (oral or IV), oxygen supplementation, and monitoring. Nasal suctioning should be gentle, performed before feeds and sleep; frequent deep suctioning is not better and may cause mucosal trauma. Supplemental oxygen is indicated when SpO2 is consistently below 90 percent (the AAP guideline threshold, though some institutions use 92 percent). High-flow nasal cannula (HFNC) is increasingly used for moderate to severe bronchiolitis, providing heated humidified oxygen with a CPAP effect that may reduce intubation rates, though it is not yet universally recommended as first-line. IV or nasogastric fluids are used for infants unable to maintain adequate oral intake.

Management — What Does NOT Work

Despite clear AAP guidelines from 2014 (reaffirmed since), overtreatment of bronchiolitis persists. Albuterol has no benefit in bronchiolitis because the pathology is inflammation and mucus plugging, not bronchospasm. A "trial" of albuterol is commonly performed but rarely changes outcomes; if given and no objective improvement is seen, it should be stopped. Corticosteroids have no benefit in bronchiolitis (unlike in croup), with multiple large randomized controlled trials showing no benefit and potential harm. Hypertonic saline (3 percent) may modestly reduce hospitalization length, but the benefit is inconsistent across studies and is generally reserved for inpatients rather than the ED. Chest physiotherapy is not recommended. Antibiotics are not indicated unless a concurrent bacterial infection is documented.

Risk Factors for Severe Disease

Risk factors for severe bronchiolitis include age under 12 weeks, prematurity (less than 37 weeks), congenital heart disease (especially hemodynamically significant lesions), chronic lung disease such as bronchopulmonary dysplasia, immunodeficiency, and neurologic or neuromuscular disease.

Admission Criteria

Admission is indicated for persistent respiratory distress (marked retractions, tachypnea), hypoxia (SpO2 below 90 percent on room air), inability to maintain hydration orally, apnea episodes, high-risk comorbidities, and unreliable caregiver access to follow-up.

Pediatric Community-Acquired Pneumonia

Etiology by Age

In neonates under 1 month, the common organisms are Group B Streptococcus, E. coli, Listeria, and HSV. From 1 to 3 months, Chlamydia trachomatis (presenting with a staccato cough and afebrile illness), RSV, and Streptococcus pneumoniae are common. From 3 months to 5 years, viral causes are most common, followed by Streptococcus pneumoniae and, emerging in this age group, Mycoplasma. In children over 5 years, Mycoplasma pneumoniae (the classic "walking pneumonia"), Streptococcus pneumoniae, and Chlamydophila pneumoniae predominate.

Clinical Presentation

The presentation includes cough, fever, tachypnea (the most sensitive sign for pneumonia in children), and retractions. The WHO tachypnea thresholds by age are: more than 60 breaths per minute for 0 to 2 months, more than 50 for 2 to 12 months, more than 40 for 1 to 5 years, and more than 20 for children over 5 years. Abdominal pain may be the presenting complaint in lower lobe pneumonia because of referred diaphragmatic pain. Auscultation reveals crackles, decreased breath sounds, or bronchial breath sounds.

Diagnosis

The diagnosis is clinical in most cases. A chest X-ray is not routinely needed for suspected uncomplicated community-acquired pneumonia treated as an outpatient, per IDSA and PIDS guidelines. Indications for imaging include hypoxia, significant respiratory distress, treatment failure, and concern for complicated pneumonia (effusion, empyema, abscess). Blood cultures are not routinely needed for well-appearing children treated as outpatients but should be obtained if the child is hospitalized.

Treatment

For outpatient treatment of presumed bacterial pneumonia in children under 5 years, high-dose amoxicillin at 90 mg/kg per day divided twice daily (targeting S. pneumoniae) is first-line. For children 5 years and older, amoxicillin with or without azithromycin (to cover atypical organisms) is appropriate. For suspected atypical pneumonia in children 5 years and older, azithromycin at 10 mg/kg on day 1 followed by 5 mg/kg on days 2 through 5 is used. Inpatient treatment involves ampicillin IV for uncomplicated non-ICU cases, or ceftriaxone with or without azithromycin. The duration is 5 to 7 days for uncomplicated community-acquired pneumonia, as shorter courses are as effective as longer ones for mild disease.

Complicated Pneumonia

Parapneumonic effusion progressing to empyema should be suspected when fever persists despite 48 hours of appropriate antibiotics, and a chest X-ray or ultrasound should be obtained. Lung abscess appears as a cavity with an air-fluid level. Necrotizing pneumonia is more common with S. aureus (including MRSA) and Streptococcus pyogenes. Management involves chest tube or video-assisted thoracoscopic surgery (VATS) for empyema and prolonged antibiotics for abscess.

<image>An illustration comparing the upper airway anatomy in croup versus epiglottitis versus normal. Three lateral neck diagrams side by side. Normal: patent airway with normal epiglottis and subglottic region. Croup: subglottic narrowing with mucosal edema below the vocal cords (the "steeple" on AP view is shown as an inset X-ray), normal epiglottis. Epiglottitis: swollen, cherry-red epiglottis (thumbprint sign on lateral X-ray shown as inset), normal subglottic region. Key distinguishing features are listed below each: croup (barky cough, gradual onset, 6 months-3 years), epiglottitis (drooling, rapid onset, toxic appearance, no barky cough).</image>

<image>A management algorithm for bronchiolitis. Starting with "Infant with clinical bronchiolitis" leading to: assess severity (respiratory rate, work of breathing, SpO2, feeding ability). Mild (no hypoxia, feeding well): nasal suctioning, anticipatory guidance, discharge with return precautions. Moderate (mild hypoxia, some feeding difficulty): supplemental O2 if SpO2 less than 90%, nasal suctioning, consider NG/IV fluids, observe. Severe (significant hypoxia, marked distress, apnea): high-flow nasal cannula, IV fluids, continuous monitoring, consider ICU. A large red "X" marks through boxes labeled albuterol, corticosteroids, antibiotics, and chest physiotherapy, with the notation "NOT recommended per AAP guidelines — no evidence of benefit."</image>

<image>A table comparing the three major pediatric respiratory emergencies: croup, bronchiolitis, and pneumonia. For each: typical age (croup 6 months-3 years, bronchiolitis less than 12 months, pneumonia any age), common causative agents, key symptoms (barky cough/stridor vs. wheezing/crackles vs. fever/tachypnea/crackles), diagnosis method (clinical vs. clinical vs. clinical ± CXR), treatment (dexamethasone ± racemic epinephrine vs. supportive care only vs. antibiotics if bacterial), and key pitfall (confusing with epiglottitis vs. giving unnecessary albuterol/steroids vs. unnecessary CXR leading to antibiotic overuse).</image>

Clinical Pearls

Dexamethasone benefits all severities of croup, and even mild croup deserves a single dose, with the oral route preferred over intramuscular. After racemic epinephrine for croup, patients must be observed for 2 to 4 hours for rebound and should not be discharged immediately. Bronchiolitis management is supportive only, and albuterol and steroids do not work; treatments that show no objective improvement should be stopped. Chest X-ray in bronchiolitis leads to unnecessary antibiotics, so routine imaging should be avoided. Tachypnea is the most sensitive sign of pneumonia in children, and age-appropriate thresholds should be used. Abdominal pain can be the presenting symptom of lower lobe pneumonia in children and should always be considered in the differential. High-dose amoxicillin at 90 mg/kg per day is first-line for outpatient pediatric community-acquired pneumonia in children under 5 years. Apnea in bronchiolitis is most concerning in infants under 2 months and premature infants, and these patients require admission and monitoring.

References

• Bjornson CL, Johnson DW. Croup in children. CMAJ. 2013;185:1317-1323.
• Ralston SL, et al. Clinical practice guideline: the diagnosis, management, and prevention of bronchiolitis (AAP). Pediatrics. 2014;134:e1474-e1502.
• Bradley JS, et al. The management of community-acquired pneumonia in infants and children (IDSA/PIDS). Clin Infect Dis. 2011;53:e25-e76.
• Russell KF, et al. Glucocorticoids for croup. Cochrane Database Syst Rev. 2011;1:CD001955.
• Gadomski AM, Scribani MB. Bronchodilators for bronchiolitis. Cochrane Database Syst Rev. 2014;6:CD001266.

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