Croup

Etiology

Etiology is most commonly viral, with some cases caused by bacteria. 

Viral

• Parainfluenza virus most commonly causes viral croup or acute laryngotracheitis, primarily types 1 and 2.
• Other causes include influenza A and B, measles, adenovirus, and respiratory syncytial virus (RSV).
• Spasmodic croup is caused by viruses that also cause acute laryngotracheitis, but lack signs of infection.

Bacterial

• Bacterial croup is divided into laryngeal diphtheria, bacterial tracheitis, laryngotracheobronchitis, and laryngotracheobronchopneumonitis.
• Laryngeal diphtheria is caused by Corynebacterium diphtheriae. Bacterial tracheitis, laryngotracheobronchitis, and laryngotracheobronchopneumonitis typically begin as viral infections, which worsen due to secondary bacterial growth.
• The common bacterial causes are Staphylococcus aureus, Streptococcus pneumoniae, Hemophilus influenzae, and Moraxella catarrhalis.

Epidemiology

Annually in the United States, croup accounts for 7% of hospitalizations in children younger than five years of age.[1] Croup affects about 3% of children per year, typically between the ages of 6 months and three years.[2] Parainfluenza virus accounts for more than 75% of croup infections. It is more common in boys than girls with a 1.5:1 ratio. Approximately 85% of cases are defined as mild croup, and less than 1% are considered severe croup.

Pathophysiology

Croup causes swelling of the larynx, trachea, and large bronchi due to infiltration of white blood cells. Swelling results in partial airway obstruction which, when significant, results in dramatically increased work of breathing, and the characteristic turbulent, noisy airflow known as stridor.

History and Physical

Croup is characterized by a "seal-like barking" cough, stridor, hoarseness, and difficulty breathing, which typically becomes worse at night. Agitation worsens the stridor, and it can be heard at rest. Other symptoms include fever and dyspnea, but the absence of fever should not reduce suspicion for croup. Respiratory rate and heart rate may also be increased with a normal respiratory rate being between 20 to 30 breaths per minute. Visual inspection of nasal flaring, retraction, and rarely cyanosis increases suspicion for croup.

Typical Presentation

• One to 2 days of upper respiratory infection (URI) followed by barking cough and stridor
• Low-grade fever
• No drooling or dysphagia
• Duration is 3 to 7 days with the most severe symptoms on days 3 or 4

Evaluation

The most commonly used system for classifying the severity of croup is the Westley score ranging from 0 to 17 points divided by five factors: stridor, retractions, cyanosis, level of consciousness, and air entry.

• Inspiratory stridor: 0 (None); 1 (When agitated); 2 (At rest)
• Retractions: 0 (None); 1 (Mild); 2 (Moderate); 3 (Severe)
• Air entry: 0 (Normal); 1 (Decreased); 2 (Markedly decreased)
• Cyanosis: 0 (None); 4 (When crying); 5 (At Rest)
• Level of consciousness: 0 (Alert); 5 (Disoriented)

Westley score less than or equal to 2 indicates mild croup.

Westley score between 3 to 5 indicates moderate croup.

Westley score between 6 to 11 indicates severe croup, and a score greater than 12 indicates impending respiratory failure.

More than 85% of children present with mild disease; severe croup is rare (less than 1%).

Croup is typically a clinical diagnosis based on signs and symptoms.

• Consider nasal washings for influenza, Respiratory syncytial virus, and parainfluenza serologies.
• Rule out other obstructive conditions, such as epiglottitis, an airway foreign body, subglottic stenosis, angioedema, retropharyngeal abscess, and bacterial tracheitis.
• A frontal x-ray of the neck may be considered but is not routinely performed. It may show a characteristic narrowing of the trachea in 50% of cases, known as the steeple sign, because of the subglottic stenosis, which resembles a steeple.
• Blood tests and viral culture are advised against, as they may cause unnecessary agitation and lead to further airway swelling and obstruction.
• Viral cultures, via nasopharyngeal aspiration, can confirm the cause but are usually restricted to research settings.
• Consider primary or secondary bacterial etiology if a patient is not responding to standard treatments.

Treatment / Management

Treatment depends on the severity based on the Westley croup score. Children with mild croup defined as Westley croup score less than 2 are given a single dose dexamethasone. Children with moderate to severe croup defined as a Westley croup score greater than 3 are given nebulized epinephrine in addition to dexamethasone.[3] Patients with diminished oxygen saturation should receive supplemental oxygen. Moderate to severe cases require up to 4 hours of observation, and if the symptoms do not improve, admission is required.

Steroids

• Corticosteroids, such as dexamethasone, results in faster resolution of symptoms, decreased return to medical care, and decreased length of stay.[4]
• Dexamethasone is superior to budesonide for improving symptom scores, but there is no difference in readmission rates.
• Dexamethasone at a dose of 0.15 mg/kg, 0.3 mg/kg, and 0.6 mg/kg all appear to be equally effective, 0.6 mg/kg is the most commonly used.
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Epinephrine

• For moderate to severe cases, nebulized racemic epinephrine has been found to improve symptom scores at 30 minutes, but the benefits may wear off after 2 hours. Current recommendations advocate for a prolonged period of observation in patients receiving racemic epinephrine. If symptoms do not worsen after 4 hours of observation, consider discharge home with close follow-up.
• 0.5 mL per kg of L-epinephrine 1:1000 via nebulizer was more effective than racemic epinephrine at two hours because of its longer effects.[5]
(A1)

Oxygen

• Deliver oxygen by "blow-by" administration as it causes less agitation than the use of a mask or nasal cannula.

Intubation

• Approximately 0.2% of children require endotracheal intubation for respiratory support.
• Use the tube that is a one-half size smaller than normal for age/size of the patient to account for airway narrowing due to swelling and inflammation.

Hot Steam

• Studies have not demonstrated a significant improvement with the administration of inhaled hot steam or humidified air.

Cough Medicine

• Cough medicines, which usually contain dextromethorphan or guaifenesin, are discouraged.

Heliox

• Little evidence supports the routine use of heliox in the treatment of croup.

Antibiotics

• Croup is most commonly a viral disease. Antibiotics are reserved for cases when primary or secondary bacterial infection is suspected.
• In cases of secondary bacterial infection, vancomycin and cefotaxime are recommended.
• In severe cases associated with influenza A or B, antiviral neuraminidase inhibitors may be used.

Differential Diagnosis

Differential diagnosis includes bacterial tracheitis, epiglottitis, foreign body aspiration, hemangioma, peritonsillar abscess, neoplasm, retropharyngeal abscess, and smoke inhalation. It is extremely important to distinguish croup with epiglottitis because of the rapid deterioration in patients. A cough is highly sensitive and specific for croup, whereas drooling is highly sensitive and specific for epiglottis.[6] Other symptoms to watch for in children with epiglottitis include acute onset dysphagia, odynophagia, high fever, and muffled voice. Children with peritonsillar abscess can have a sore throat, fever, and the classic "hot potato" voice. Children with retropharyngeal abscess can also have a fever, drooling, dysphagia, odynophagia but also have neck pain with a bulging posterior pharyngeal wall on neck radiography.