# Croup, Epiglottitis, and Upper Airway Emergencies

## Introduction

Upper airway emergencies in children are among the most anxiety-provoking presentations in pediatric medicine. The pediatric airway is anatomically narrower and more susceptible to obstruction than the adult airway. Even modest mucosal edema can produce significant airflow limitation, since resistance to airflow is inversely proportional to the fourth power of the radius (Poiseuille's law). Croup (laryngotracheobronchitis) is the most common cause of acute upper airway obstruction in children, while epiglottitis, once a leading cause of airway emergencies, has become rare due to the Hib vaccine. This lecture covers the differential diagnosis, assessment, and management of these critical conditions.

## Anatomy of the Pediatric Airway

The narrowest point of the pediatric airway is the subglottic region at the level of the cricoid cartilage in children under 8 years. The larynx is higher (C3-C4) and more anterior compared to adults. The epiglottis is omega-shaped and floppier in infants. One millimeter of circumferential edema in the subglottic space reduces the cross-sectional area by approximately 60% in an infant. Infants are obligate nasal breathers until approximately 4-6 months of age.

<image>Cross-sectional anatomical comparison of the pediatric airway versus the adult airway at the subglottic level, demonstrating how 1 mm of mucosal edema causes proportionally greater airway narrowing in the smaller pediatric airway, with calculations showing percentage reduction in cross-sectional area</image>

## Croup (Laryngotracheobronchitis)

### Epidemiology and Etiology

Croup is the most common cause of stridor in children aged 6 months to 3 years, with peak incidence in the fall and winter months. Parainfluenza virus (types 1 and 3) is the most common etiology, accounting for approximately 75% of cases. Other causes include RSV, influenza, adenovirus, human metapneumovirus, rhinovirus, and rarely Mycoplasma pneumoniae.

### Clinical Presentation

The illness begins with prodromal URI symptoms (rhinorrhea, low-grade fever) for 1-3 days, followed by the hallmark barking (seal-like) cough. Inspiratory stridor indicates extrathoracic airway obstruction. Hoarseness results from laryngeal involvement. Symptoms are classically worse at night and may fluctuate. The typical duration is 3-7 days, with peak severity on days 2-3.

### Severity Assessment (Westley Croup Score)

Mild croup presents with intermittent barking cough, no stridor at rest, and no retractions. Moderate croup features frequent barking cough, stridor at rest, and mild to moderate retractions without distress. Severe croup involves stridor at rest, significant retractions, decreased air entry, agitation or lethargy, and possible cyanosis.

### Management

Keeping the child calm is essential, as agitation worsens dynamic airway obstruction; allowing the child to remain in the parent's lap is recommended. Dexamethasone at 0.6 mg/kg (PO or IM, maximum 10 mg) is given as a single dose and is effective for all severities, with onset in 2-4 hours and duration up to 72 hours. Nebulized racemic epinephrine (0.5 mL of 2.25% solution in 3 mL NS) or L-epinephrine (0.5 mL/kg of 1:1000, maximum 5 mL) is used for moderate to severe croup, with onset in minutes and duration of 1-2 hours. Patients should be observed for a minimum of 2-4 hours after racemic epinephrine for rebound stridor. Humidified air and mist therapy have no evidence of benefit in randomized trials despite historical use. Heliox (70:30 helium-oxygen mixture) reduces turbulent airflow in severe cases as a bridge. Intubation is rarely needed (less than 1%), and when required, an ETT 0.5-1.0 sizes smaller than predicted should be used.

## Epiglottitis (Supraglottitis)

### Epidemiology and Etiology

Epiglottitis was historically caused by Haemophilus influenzae type b (Hib) in children aged 2-7 years, but its incidence has decreased by more than 99% since the introduction of the Hib vaccine. Current etiologies include Streptococcus pyogenes, Staphylococcus aureus, Streptococcus pneumoniae, and non-typeable H. influenzae. It is now more common in adults and immunocompromised children.

### Clinical Presentation

Epiglottitis has a rapid onset (hours) with high fever, sore throat, dysphagia, and drooling. The child appears toxic and sits in the tripod position (leaning forward, neck extended, mouth open). A muffled "hot potato" voice (not hoarseness) is characteristic. The absence of cough distinguishes epiglottitis from croup. Inspiratory stridor is a late finding indicating severe obstruction. The classic presentation is summarized by the "4 D's": dysphagia, drooling, distress, and dysphonia.

### Diagnosis

Epiglottitis is a clinical diagnosis, and definitive airway management should not be delayed for imaging. If the patient is stable enough for imaging, a lateral neck radiograph shows the "thumb sign" (swollen epiglottis). Direct visualization in the operating room reveals a cherry-red, edematous epiglottis. Blood cultures and epiglottic surface cultures should be obtained.

### Management

The child should not be agitated -- throat examination, IV placement, and laying the child supine should all be avoided until the airway is secured. Anesthesiology and ENT/otolaryngology should be called immediately. Controlled intubation in the operating room under inhalational anesthesia is the safest approach. IV antibiotics include ceftriaxone (50-100 mg/kg/day) or ampicillin-sulbactam, with vancomycin added if MRSA is suspected. The duration of intubation is typically 24-72 hours, until an air leak develops around the ETT. Close contacts require rifampin prophylaxis if there are unvaccinated household contacts under 4 years.

<image>Side-by-side lateral neck radiograph illustrations comparing a normal epiglottis with the "thumb sign" of acute epiglottitis, and an anteroposterior view showing the "steeple sign" of subglottic narrowing in croup, with anatomical labels and clinical correlations</image>

## Comparison of Upper Airway Emergencies

| Feature | Croup | Epiglottitis | Bacterial Tracheitis |
|---------|-------|-------------|---------------------|
| Age | 6 months - 3 years | 2-7 years (rare now) | 6 months - 8 years |
| Onset | Gradual (days) | Rapid (hours) | URI prodrome then toxic |
| Fever | Low-grade | High | High |
| Cough | Barky (seal-like) | Absent | Present, productive |
| Voice | Hoarse | Muffled ("hot potato") | Variable |
| Drooling | No | Yes | Variable |
| Position | Comfortable | Tripod | Variable |
| Stridor | Inspiratory | Late finding | Inspiratory |
| Response to racemic epi | Yes | No | No |
| Etiology | Parainfluenza (75%) | GAS, S. aureus (post-Hib vaccine) | S. aureus |
| Key imaging | Steeple sign (AP) | Thumb sign (lateral) | Intraluminal membranes (CT) |
| Treatment | Dexamethasone ± racemic epi | Airway + IV antibiotics | Intubation + IV antibiotics |

## Differential Diagnosis of Upper Airway Obstruction

### Bacterial Tracheitis

Bacterial tracheitis is a life-threatening infection of the trachea, often following a viral URI or croup. It is most commonly caused by Staphylococcus aureus, with Streptococcus pyogenes and Moraxella catarrhalis as other pathogens. The child has high fever, appears toxic, produces purulent secretions, and does not respond to nebulized epinephrine. Diagnosis is made by endoscopy revealing purulent tracheal membranes, and CT of the neck may show subglottic narrowing with intraluminal membranes. Management involves intubation (often required), IV antibiotics (vancomycin plus ceftriaxone), and ICU admission.

### Retropharyngeal Abscess

Retropharyngeal abscess is an infection of the retropharyngeal space, most common in children under 4 years before lymph node involution. It presents with fever, neck stiffness, refusal to eat, drooling, torticollis, and neck swelling. Lateral neck radiograph shows prevertebral soft tissue widening (greater than 7 mm at C2, greater than 14 mm at C6). CT of the neck with IV contrast is the gold standard for diagnosis. Management includes IV antibiotics (ampicillin-sulbactam or clindamycin), with surgical drainage if the abscess is greater than 2 cm, there is worsening despite antibiotics, or airway compromise is present.

### Peritonsillar Abscess

Peritonsillar abscess is most common in adolescents and presents with unilateral sore throat, trismus, muffled voice, and uvular deviation away from the affected side. Management involves needle aspiration or incision and drainage, antibiotics, and pain management.

### Foreign Body Aspiration

Foreign body aspiration has peak incidence in children 6 months to 3 years and presents with a witnessed choking event, acute onset of cough, and unilateral wheezing or decreased breath sounds. Rigid bronchoscopy is used for diagnosis and removal.

<image>Clinical decision algorithm for a child presenting with stridor, differentiating between croup, epiglottitis, bacterial tracheitis, retropharyngeal abscess, and foreign body aspiration based on clinical features including onset, fever, cough quality, drooling, position of comfort, and response to treatment</image>

## Clinical Pearls

A single dose of dexamethasone (0.6 mg/kg) is effective for all severities of croup and reduces return visits and hospitalization. Patients should be observed for at least 2-4 hours after racemic epinephrine due to the risk of rebound symptoms. Epiglottitis is now rare in vaccinated children, and when present, the pharynx should not be examined; instead, a calm environment should be maintained and controlled airway management arranged. Bacterial tracheitis should be suspected when a child with croup fails to improve with standard therapy and appears toxic. The absence of cough and the presence of drooling favor epiglottitis over croup. Foreign body aspiration should always be considered in the acute onset of stridor or wheezing without preceding illness.

## References

1. Bjornson CL, Johnson DW. Croup in children. *Canadian Medical Association Journal*. 2013;185(15):1317-1323.
2. Cherry JD. Croup (laryngotracheobronchitis). In: Cherry JD, Harrison GJ, Kaplan SL, et al., eds. *Feigin and Cherry's Textbook of Pediatric Infectious Diseases*. 8th ed. Elsevier; 2019.
3. Shah RK, Roberson DW, Jones DT. Epiglottitis in the Hemophilus influenzae type B vaccine era: changing trends. *Laryngoscope*. 2004;114(3):557-560.
4. Russell KF, Liang Y, O'Gorman K, Johnson DW, Klassen TP. Glucocorticoids for croup. *Cochrane Database of Systematic Reviews*. 2011;(1):CD001955.