Croup (acute laryngotracheobronchitis)

Refers to respiratory illnesses with inspiratory strider, barking cough, and hoarseness due to obstruction of the larynx.

Croup, also known as laryngotracheobronchitis, is a type of respiratory infection that is usually caused by a virus.

Viral croup or acute laryngotracheitis is most commonly caused by parainfluenza virus primarily types 1 and 2, in 75% of cases.

Other viral agents include influenza A and B, measles, adenovirus and respiratory syncytial virus (RSV)

The virus causing croup leads to swelling of the larynx, trachea, and large bronchi, due to infiltration of white blood cells especially histiocytes, lymphocytes, plasma cells, and neutrophils.

Bacterial croup may be divided into laryngeal diphtheria, bacterial tracheitis, laryngotracheobronchitis, and laryngotracheobronchopneumonitis.

Bacterial tracheitis, laryngotracheobronchitis, and laryngotracheobronchopneumonitis are usually due to a primary viral infection with secondary bacterial growth: most common bacteria implicated are Staphylococcus aureus, Streptococcus pneumoniae, Hemophilus influenzae, and Moraxella catarrhalis.

Laryngeal diphtheria is due to Corynebacterium diphtheriae.

Bacterial infection is considered if a person does not improve with standard management.

85% of children presenting to the emergency department have mild disease.

Severe croup is rare occurring in less than 1% of cases.

It is slightly more common in males.

Occurs most often in autumn.

Stridor is worsened by agitation or crying, and may indicate critical narrowing of the airways.

Can can be caused by a number of viruses including parainfluenza and influenza virus, and is rarely due to a bacterial infection.

It leads to swelling in the trachea, which interferes with normal breathing and produces the classic symptoms of barking cough, stridor, a hoarse voice, difficulty breathing.

The airway swelling produces airway obstruction which, leads to dramatically increased work of breathing and the characteristic turbulent, noisy airflow known as stridor.

Occurs annually in 3% of children under the age of 6 years.

Rarely seen in children as old as fifteen.

Patients may experience fever and runny nose.

Symptoms range from mild, moderate, or severe.

Deaths are rare.

Croup can very rarely result in death from respiratory failure and/or cardiac arrest.

Uncommon complications include bacterial tracheitis, pneumonia, and pulmonary edema.

Symptoms starts or is worse at night.

Viral croup is usually a self-limiting process.

Half of cases resolve in 1 day.

80% of cases of croup resolve in two days.

As noted symptoms usually improve within two days, but may last for up to seven days.

Affects about 15% of children, and usually presents between the ages of 6 months and 5–6 years.

It accounts for about 5% of hospital admissions in this population.

It may occur in children as young as 3 months and as old as 15 years.

Peak incidence between 7 and 36 months.

There is an increased prevalence in autumn.

As many as 15% of all children have at least one episode of disease and five percent have it more than once.

Boy:girl ratio 1.5:1.

Acute inflammation with erythema and edema of the trachea below the vocal cords.

Secondary to viral infections with nearly three-fourths related to parainfluenza viruses, less commonly influenza virus or respiratory syncytial virus and to other viruses as well.

Spread of viruses from child to child via infected mucous or saliva.

Cellular infiltration of neutrophils, histiocytes, lymphocytes and plasma cells.

With bacterial croup there is inflammation with the addition of micro abscesses, pseudomembranes and ulcerations causing the formation of purulent material in the trachea and lower air passages.

With spasmodic croup edema without inflammation is present in the subglottic area.

The subglottic area is the narrowest point of the airway in toddlers, and is the site of the symptoms.

Crowing sound is made by turbulence of air flow in small airways, ref2242ed to as stridor.

Breathing associated with seal-like barking and rib retractions.

Worse at night and stridor onset may be very sudden.

Allergy may play a role in recurrent disease.

Must be distinguished from epiglottitis, angioneurotic edema of the glottis, or foreign bodies causing upper airway obsruction

Fewer than 5% of children with croup require hospitalization and 1-2% require intubation.

Peak time is fall and early winter, but can occur at any time of the year.

Westley croup score is based on five criteria: severity of retractions, degree of stridor, degree of air movement, presence of cyanosis and alertness.

Many cases have been prevented by immunization for influenza and diphtheria.

A clinical diagnosis.

Differential diagnosis:


airway foreign body

bacterial tracheitis

It is diagnosed based on signs and symptoms.

Diagnosis requires exclusion of other obstructive conditions of the upper airway, especially epiglottitis, an airway foreign body, subglottic stenosis, angioedema, retropharyngeal abscess, and bacterial tracheitis.

An X-ray of the neck may show a narrowing of the trachea, called the steeple sign, because of the subglottic stenosis, which resembles a steeple in shape.

The steeple sign is suggestive of the diagnosis, but is seen in only half of cases.

Other testing,cultures not necessary for diagnosis.

Prevention: Influenza and diphtheria vaccinations.

Score divided into mild, moderate and severe disease.

Treatment includes the use of mist which relieves raspy and dry throat, helps loosen airway mucous and improves expectoration.

Usually treated with a single dose of steroids by mouth.

In more severe cases inhaled epinephrine may also be used.

Children with oxygen saturations under 92% should receive oxygen,

Less than 0.2% of children require endotracheal intubation.

Hospitalization may be required in one to five percent of cases.

Corticosteroid usage results in significant benefits even in patients with mild disease.

Viral infection leading to inflammation of the upper airway and subglottic obstruction.

Corticosteroids decreases the frequency and duration of hospitalization and need for intubation.

Steroid relief is obtained as early as two hours after administration: given by injection, by inhalation, and giving the medication by mouth is pref2242ed.

In cases of suspected secondary bacterial infection, antibiotics are recommended.

In severe cases associated with influenza A or B, the antiviral neuraminidase inhibitors may be administered.

Croup may be improved temporarily with nebulized epinephrine, with benefits lasting for only about 2 hours.

Since croup is usually a viral disease, antibiotics are not used unless secondary bacterial infection is suspected.

Humidity treatment, despite frequent use, does not result in benefits in children with moderate disease and treated in the emergency department.

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