Croup

Educational clinical summary of Croup for doctors and students: definition, workup, management, and key caveats. Not a substitute for guidelines.

Maintained by Dr. Vivek Karn Review process: editorial policy

DISCLAIMER: This information is intended for clinical reference only and should not replace individual clinical judgment, current institutional protocols, or consultation with relevant specialists. Dosing, specific management, and criteria must be adjusted based on the individual patient's status and current evidence.

Overview

Definition

Croup, or acute laryngotracheobronchitis, is a common pediatric respiratory illness characterized by acute inflammation and edema of the subglottic airway (larynx, trachea, and bronchi). This inflammation leads to airway narrowing, resulting in the characteristic inspiratory stridor, barking cough, and hoarseness.

Epidemiology

Incidence: Extremely common, particularly in infants and toddlers.
Age Range: Primarily affects children aged 6 months to 3 years. Incidence decreases significantly after age 6.
Sex: Slightly higher incidence in males than females.
Seasonality: Peak incidence occurs during the late autumn and winter months, aligning with typical viral respiratory season.
Etiology: The vast majority (>80%) of cases are caused by Parainfluenza Virus Type 1 (PIV-1). Other common viral causes include PIV-2, PIV-3, Respiratory Syncytial Virus (RSV), Influenza A and B, Adenovirus, and Measles (rarely).

Classification

Croup severity is commonly classified using the Westley Croup Score, which guides management:

Parameter	Score 0	Score 1	Score 2	Score 3	Score 4	Score 5
Stridor	None	With agitation	At rest	-	-	-
Retractions	None	Mild	Moderate	Severe	-	-
Air Entry	Normal	Mild decrease	Marked decrease	-	-
Color	Normal	-	-	-	-	Cyanosis
Level of Consciousness	Normal	-	Sluggish	-	-	Depressed

Mild Croup (Score ≤ 2): Barking cough, hoarseness, no stridor at rest, mild or no chest wall retractions.
Moderate Croup (Score 3–7): Stridor at rest, moderate retractions, and little or no agitation.
Severe Croup (Score 8–11): Significant stridor at rest, marked retractions, signs of decreased air entry, and possibly lethargy or restlessness.
Impending Respiratory Failure (Score $\geq$ 12): Exhaustion, decreased level of consciousness, cyanosis, and poor air entry.

Pathophysiology

Mechanism

Croup is an inflammatory response, nearly always viral, primarily targeting the laryngeal and tracheal mucosa. 1. Infection: Viral replication occurs in the epithelial cells of the upper respiratory tract. 2. Inflammation: Immune response leads to mucosal edema, cellular infiltration (mononuclear and polymorphonuclear cells), and hyperemia. 3. Airway Narrowing: The subglottic region, which is the narrowest point of the pediatric airway and surrounded by a rigid cricoid cartilage ring, is particularly susceptible. Edema in this area (around the vocal cords and conus elasticus) drastically reduces the cross-sectional area. 4. Turbulent Airflow: Narrowed airways require increased negative inspiratory pressure, leading to the characteristic turbulent flow manifested as a barking cough and inspiratory stridor. Crying or agitation exacerbates negative intrathoracic pressure, worsening stridor.

Risk Factors

Age 6 months to 3 years.
History of recurrent croup (suggesting a smaller basal airway diameter).
Seasonal timing (fall/winter).
Exposure to other sick contacts.

Protective Factors

Increasing age (airway diameter increases).
Vaccination against influenza (if influenza is the etiology).
Immunocompetence.

Clinical Presentation

Signs and Symptoms

Cardinal Features

Barking (Seal-like) Cough: The most characteristic symptom.
Inspiratory Stridor: High-pitched, noisy breathing primarily heard during inspiration.
Hoarseness: Due to vocal cord edema.
Recent Upper Respiratory Prodrome: Often preceded by 12–48 hours of rhinorrhea, congestion, and low-grade fever.

Early Signs

Rhinitis, pharyngitis, low-grade fever ($\approx 38.0^{\circ} \text{C}$).
Cough, initially dry and irritating, progressing to the barking quality.
Symptoms often worsen at night due to cooler air, gravitational pooling of secretions, and decreased sympathetic tone.

Advanced Signs (Severe Croup/Respiratory Failure)

Stridor heard immediately upon presentation without agitation.
Severe suprasternal, sternal, and intercostal retractions.
Tachypnea and Tachycardia (compensatory).
Pallor, cyanosis (late sign, indicating severe hypoxemia).
Altered mental status (lethargy, decreased responsiveness, or extreme restlessness/anxiety).

Atypical Presentations

Spasmodic Croup: Sudden onset, severe barking cough, and stridor, often with little or no fever or URI prodrome. Symptoms are recurrent and typically subside quickly. Thought to be related to hypersensitivity or allergy, but treatment remains similar.

Physical Examination

Inspection

Vital Signs: Assess temperature, respiratory rate (often elevated), and pulse oximetry ($\text{SpO}_2$).
Respiratory Effort: Observe for signs of distress (flaring, accessory muscle use).
Retractions: Note location and severity (suprasternal, subcostal, intercostal).
Stridor: Characterize (inspiratory, biphasic, presence while resting). Biphasic or purely expiratory stridor suggests more distal lower airway obstruction or severe obstruction.
Air Entry: Assess symmetry and adequacy (severe obstruction leads to decreased air entry).
Mental Status: Assess for alertness, agitation, and signs of hypoxia (confusion, lethargy).

Palpation

Pulse: Tachycardia is common with fever/distress.
Cervical Lymphadenopathy: Often mild or absent, but important to check to rule out bacterial causes (e.g., epiglottitis, although rare).

Special Tests

Acoustic Characteristics: Carefully listen to the quality of the cough and stridor.
Assessment of Severity: Use the Westley Croup Score in the initial assessment and throughout management to trend improvement or deterioration.

Diagnostic Approach

The diagnosis of Croup is primarily clinical, based on the characteristic presentation (barking cough, stridor, recent URI prodrome) in an appropriate age group.

History Taking

Key Questions

Onset and Duration: When did the cough and stridor begin? Is this acute or recurrent?
Progression: Has the stridor worsened, or is the child better/worse at night?
Associated Symptoms: Fever, preceding cold symptoms, difficulty swallowing (suggests epiglottitis).
Immunization Status: Vaccination against H. influenzae type b (Hib) and Diphtheria (to exclude epiglottitis and diphtheria).

Red Flags (Suspecting Alternative Diagnosis or Severe Disease)

Toxic Appearance: Ill-appearing child, high fever ($>39.0^{\circ} \text{C}$).
Muffled Voice or Drooling: Suggestive of Epiglottitis (though significantly less common now due to Hib vaccination).
Rapid Progression to Severe Distress: Suggests bacterial tracheitis or epiglottitis.
No Response to Nebulized Epinephrine: Indicates unresponsive or very severe fixed airway obstruction.
Atypical Age: Presentation in adolescents or adults (consider mass, tumor, foreign body, angioedema).

Laboratory Tests

Laboratory tests are generally not required for the routine management of mild to moderate croup.

First-Line

Pulse Oximetry: Essential for all patients with stridor at rest or moderate/severe respiratory distress. $\text{SpO}_2 < 92\%$ on room air suggests severe disease or impending failure.

Confirmatory

Viral Panels (e.g., PCR/Multiplex Respiratory Assay): Rarely indicated unless admission is required or for surveillance/epidemiologic purposes (e.g., confirming Influenza or COVID-19).

Monitoring

Arterial Blood Gas (ABG): Only in impending respiratory failure or if mechanical ventilation is considered. Reveals hypercapnia ($\text{pCO}_2 > 50\text{ mmHg}$) and severe distress.

Imaging

Plain radiography is generally not indicated and should be avoided in children with stridor if the clinical picture is classic for croup, as obtaining images may agitate the child and worsen obstruction.

Neck Radiograph (Anteroposterior view): Only if the diagnosis is uncertain (e.g., to rule out foreign body or epiglottitis).
- Classic Finding in Croup: The "Steeple Sign" or "Wine Bottle Sign" on the AP neck film, referring to the subglottic narrowing (appears as a symmetric, tapered shape below the vocal cords). Clinical diagnosis should still outweigh radiologic findings.

Advanced

Laryngoscopy/Bronchoscopy: Reserved for refractory cases, suspicion of foreign body aspiration, or concern for alternative, fixed anatomical lesions (e.g., subglottic stenosis). Should only be performed in a controlled environment (e.g., operating room) with airway expertise present.

Management

The cornerstone of croup management involves corticosteroids and nebulized epinephrine for moderate-to-severe disease. Management focuses on reducing subglottic edema and maintaining oxygenation. Minimizing agitation is crucial, as crying increases oxygen demand and exacerbates turbulent flow.

Acute Management

Immediate (All patients with stridor at rest or significant distress)

Airway and Breathing: Position the child comfortably (often on a parent's lap). Provide humidified oxygen if $\text{SpO}_2 < 92\%$.
Severity Assessment: Use the Westley Croup Score (or similar) to triage.

Stabilization (Moderate to Severe Croup, Westley Score 3–11)

Oxygen: Administer humidified oxygen if needed.

1. Corticosteroids (Standard of Care): Reduces inflammation and edema. * Dexamethasone: Highly effective due to its long half-life (36–72 hrs). * Dosage: 0.6 mg/kg/dose PO or IM (maximum dose 10–16 mg). Oral administration is preferred and equally effective to IM. * Rationale: Onset of action is around 1–4 hours, providing sustained relief and preventing relapse. A single dose is typically sufficient.

2. Nebulized Epinephrine (Racemic or L-Epinephrine): Used for stridor at rest (score $\geq 3$) or significant distress/hypoxia. * Mechanism: Immediate alpha-adrenergic effect causes vasoconstriction in the subglottic mucosa, rapidly reducing edema and opening the airway. * Dosage (Racemic Epinephrine - Preferred): 0.25 to 0.5 mL of 2.25% solution diluted in 3 mL of normal saline, administered via nebulizer. * Dosage (L-Epinephrine): 5 mL of 1:1,000 solution (equivalent to 5 mg), via nebulizer. * Monitoring: Monitor vital signs (especially heart rate) and respiratory status. Onset is rapid (10–30 min), but the effect is transient (lasting $\approx 2$ hours).

Emergency (Severe Croup or Impending Respiratory Failure, Westley Score $\geq$ 8)

Repeat Epinephrine: May repeat nebulized epinephrine every 15–20 minutes as needed, especially if stridor returns rapidly.
Heliox (80% He/20% $\text{O}_2$): May be considered in refractory severe croup. Reduces the density of the inhaled gas, promoting laminar flow and decreasing the work of breathing. Requires close specialist monitoring.
Intubation: Reserved for complete or near-complete airway obstruction, exhaustion, refractory hypoxia, or hypercapnia. Use the smallest cuffed endotracheal tube that passes easily, usually 0.5 to 1.0 size smaller than predicted for age, to reduce trauma to the subglottic area. Sedation may be required prior to intubation. Airway management should be performed by the most experienced provider (e.g., Anesthesia/ENT).

Chronic Management

Management is focused on acute resolution. Croup is rarely chronic.

Treatment Algorithms

Westley Score	Severity	Treatment	Discharge Criteria
0–2	Mild	Dexamethasone 0.6 mg/kg PO/IM (May consider observation/home care without steroids if very mild and stable)	Stable, good oral intake, caretaker education.
3–7	Moderate	Dexamethasone 0.6 mg/kg PO/IM PLUS Nebulized Epinephrine (Racemic or L-)	Observe for 3–4 hours post-epinephrine. Discharge if no stridor at rest, normal air entry, and SaO2 $>92\%$.
$\geq$ 8	Severe	High-priority transfer to ED/ICU. Dexamethasone 0.6 mg/kg IM/IV PLUS Nebulized Epinephrine (may repeat q15min). Oxygen for SaO2 $<92\%$.	Requires admission for continuous monitoring.

Refractory Cases

If the patient requires multiple (e.g., >2) doses of nebulized epinephrine or if symptoms return rapidly despite aggressive corticosteroid therapy, the patient must be admitted to an ICU or monitored setting to assess for developing complications (e.g., bacterial tracheitis) or fixed obstruction.

Complications

Common

Mild dehydration (due to increased respiratory effort and tachypnea).
Sleep disruption and parental anxiety.

Serious

Respiratory Failure: Due to progressive airway obstruction and exhaustion.
Secondary Bacterial Tracheitis: A rare but potentially life-threatening complication characterized by high fever, purulent sputum, and toxicity (often caused by S. aureus or Moraxella catarrhalis). Requires IV antibiotics and possible mechanical ventilation/endoscopy.
Pneumonia or Otitis Media: Secondary bacterial infections.

Long-term

Recurrence (Recurrent Croup) is common, particularly in young children. Usually benign.

Prognosis

Croup is almost always a self-limiting illness with an excellent prognosis. Symptoms typically peak on the second or third day and gradually resolve within 3–7 days.

Factors Affecting Outcome

Severity at presentation (Westley Score).
Presence of underlying chronic cardiopulmonary or airway disease.
Rapid or inadequate response to treatment (suggests alternative diagnosis).

Survival

Mortality is exceedingly low in developed countries. Severe morbidity is generally limited to rare cases of bacterial tracheitis or prolonged hypoxia.

Prevention

Primary

Hand Hygiene: Reduces transmission of viral pathogens.
Immunization: Annual influenza vaccination.

Special Populations

Pediatric

Infants (<6 months): The airway is smaller; thus, they are at higher risk for severe obstruction from less edema. Care must be aggressive, and they often warrant admission and close observation.
Atypical Presentation in Older Children (>6 years): Consider non-infectious causes of subglottic narrowing (e.g., vocal cord dysfunction, angioedema, foreign body).

Comorbidities

Pre-existing Subglottic Stenosis or Tracheomalacia: These patients have severely compromised airways and may decompensate rapidly. Aggressive management in an ICU setting is crucial.

Clinical Pearls

Diagnostic

Listen, Don't Touch: A toxic-appearing child with stridor and high fever should raise immediate concern for epiglottitis or bacterial tracheitis. In these cases, examination of the pharynx/larynx may precipitate total obstruction. Maintain vigilance and secure the airway first.
The "Steeple Sign" is Optional: Do not delay treatment or agitation a distress child to obtain a radiograph for confirmation.

Treatment

Dexamethasone is Key: Even mild croup benefits from Dexamethasone (0.6 mg/kg). This single dose prevents progression and reduces the need for subsequent interventions.
Observation Post-Epinephrine: Never send a child home immediately after nebulized epinephrine. Due to rebound laryngeal edema, the child must be observed for at least 3–4 hours after the last dose to ensure sustained improvement without recurrence of stridor at rest.

Pitfalls

Misinterpreting Clear Lungs: Auscultation may reveal clear breath sounds despite severe distress because air ingress is minimal due to the upper airway obstruction.
Dismissing Agitation: Agitation often reflects both anxiety and hypoxia. Treat both aggressively (comfort measures, non-invasive oxygen, and specific croup therapy).

Recent Updates

Guidelines

Current guidelines (e.g., AAP, Cochrane reviews) strongly support the universal use of oral or intramuscular Dexamethasone regardless of croup severity, due to its efficacy and low side-effect profile.
The use of humidified air/steam alone has been largely dismissed as an evidence-based treatment, though it may provide comfort.

Evidence

Evidence confirms that a single low dose of Dexamethasone (0.15 mg/kg) is likely effective for very mild croup, though 0.6 mg/kg remains standard for preventing recurrence and managing moderate disease. Oral administration is non-inferior to IM.

Key References

UpToDate: Croup: Clinical features, evaluation, and diagnosis.
Cochrane Database of Systematic Reviews. Glucocorticoids for Croup. (2018)
American Academy of Pediatrics (AAP) Guidelines on the management of Stridor in Children.
Westley CR, et al. The Diagnosis and Treatment of Croup. (Landmark study establishing the severity rating scale.)