Croup

Synonyms: acute laryngotracheitis, acute laryngotracheobronchitis

What is croup?

Croup is usually relatively mild and self-limiting but the distressing symptoms may prompt parents to bring their child to their GP or local emergency department. Severe cases may compromise the upper airway and so the condition of the child needs to be assessed carefully and other causes of upper airway obstruction (such as inhaled foreign body and epiglottitis) must be considered and excluded.

Causes of croup (aetiology)¹

• Viruses are detected in up to 80% of patients who have croup with identifiable pathogens.

• Parainfluenza virus (types 1 to 3) is the cause in over 75% of cases, primarily types 1 and 2.²

• Other viral causes include influenza A and B, adenovirus, respiratory syncytial virus, and measles.²

• Viral infection of the subglottic region and laryngeal mucosa causes inflammation and oedema, which significantly decrease air movement and lead to respiratory distress and stridor.

• Bacterial croup is less common and may be caused by mycoplasma pneumoniae and corynebacterium diphtheriae, as well as haemophilus influenzae, streptococcus pneumoniae or staphylococcus aureus. Routine childhood vaccinations against diphtheria and HIB protect against this.

• The type of infectious agent does not affect outcomes or initial management.

How common is croup? (Epidemiology)³

• Croup affects about 3% of children per year, mostly between the ages of 6 months and 3 years.²

• Hospital admissions due to croup peak in September to December, but occur throughout the year.

• Annually, 7% of hospitalisations in children in the USA are due to croup.²

Risk factors

• Male:female preponderance is about 1.5:1.²

• Genetic studies suggest that the C/C variant of the CD14 C-159T gene had a significantly lower prevalence of croup.⁴

Symptoms of croup (presentation)

• Croup normally starts with nonspecific symptoms of viral upper respiratory tract infection (URTI), such as runny nose, sore throat, fever and cough.

• After 1-2 days of these symptoms, the characteristic barking cough and hoarseness tends to start. These symptoms tend to be worse at night.

• There is a high degree of variability in clinical findings. There may be a mild-to-moderate fever. Check vital signs (including temperature, heart rate and respiratory rate). Heart rate and respiratory rate may be increased.

• A barking cough and hoarse cry are nearly always present.

• Stridor (harsh, low-pitched noise heard during inspiration) may be heard at rest or only when the child is agitated or active.

• Chest sounds are usually normal but can be decreased in volume where there is severe airflow limitation.

• The illness tends to last for about 3-7 days but can persist for up to two weeks. The typical croup symptoms of barking cough and stridor tend to be worst on days 3-4. ²

• A low SaO₂ on pulse oximetry (<95%) indicates significant respiratory impairment.

• Fewer than 1% of children with croup have severe symptoms. Respiratory distress with marked tachypnoea and intercostal recession may be noted. It should be recognised that intercostal recession may reduce and stridor may diminish in a child who has severe and deteriorating croup. Such a child may be at high risk of respiratory failure. Respiratory rate of over 70 breaths per minute is a factor indicating severe respiratory distress, as is increasing upper airway obstruction, sternal/intercostal recession, asynchronous chest wall and abdominal movement, fatigue, pallor or cyanosis, decreased level of consciousness or tachycardia.³

Differential diagnosis

• Epiglottitis.

• Inhaled foreign body.

• Inhaled noxious substance.

• Acute anaphylaxis.

• Bacterial tracheitis.

• Diphtheria.

• Laryngomalacia or another congenital cause of upper airway stenosis (eg, aortic arch abnormality causing external airway compression).

• Peritonsillar abscess (quinsy).

• Retropharyngeal abscess.

• Angioneurotic oedema.

• Laryngeal mucosal lesions such as laryngeal web, papillomata and haemangioma.

• Vocal cord paralysis.

Assessment of severity^{3 25}

There are many clinical scoring systems for croup.

NICE CKS advises classifying the croup into mild, moderate or severe.

• Mild - seal-like barking cough but no stridor or sternal/intercostal recession at rest.

• Moderate - seal-like barking cough with stridor and sternal recession at rest; little or no agitation or lethargy.

• Severe - seal-like barking cough with stridor and sternal/intercostal recession associated with agitation or lethargy.

• Impending respiratory failure - increasing upper airway obstruction:

  • Sternal/intercostal recession, asynchronous chest wall and abdominal movement.

  • Fatigue, pallor or cyanosis, decreased level of consciousness or tachycardia.

  • The degree of chest wall recession may diminish with the onset of respiratory failure as the child tires.

  • A respiratory rate of over 70 breaths/minute is also indicative of severe respiratory distress.

The Westley scoring system may also be used. The Westley score ranges from 0 to 17 points, involving 5 signs: 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)

A Westley score less than or equal to 2 indicates mild croup (more than 85% of children with croup fall into this category). A Westley score between 3 to 5 indicates moderate croup. A Westley score between 6 to 11 indicates severe croup, and a score greater than 12 indicates impending respiratory failure.

Hospital admission³

Admit all children with features of moderate or severe illness, or impending respiratory failure.

Children with a respiratory rate of over 60 breaths/minute or who have a high fever or 'toxic' appearance should also be admitted.

Children with mild illness may require admission if they have factors that warrant a lower threshold for admission, such as:

• Chronic lung disease (including bronchopulmonary dysplasia).

• Haemodynamically significant congenital heart disease.

• Neuromuscular disorders.

• Immunodeficiency.

• Age under 3 months.

• Inadequate fluid intake (50-75% of usual volume, or no wet nappy for 12 hours).

• Factors that might affect a carer's ability to look after a child with croup, such as adverse social circumstances, or concerns about the skill and confidence of the carer in looking after a child with croup at home, or the carer being able to spot deteriorating symptoms.

• Longer distance to healthcare in case of deterioration.

While awaiting admission to hospital:

• Give controlled supplementary oxygen if there are symptoms of severe illness or impending respiratory failure.

• Give oral dexamethasone (0.15 mg/kg).

• If the child is too unwell to receive medication, inhaled budesonide (2 mg nebulised as a single dose) or intramuscular dexamethasone (0.6 mg/kg as a single dose) are possible alternatives.

Diagnosing croup (investigations)

The diagnosis is usually made on clinical grounds but the following investigations may be indicated:

• Once in hospital, blood tests and chest x-ray are not usually required as they are usually of little clinical value and risk distressing the child and making the symptoms worse. ²

• Nasal washings may be carried out for influenza, parainfluenza or RSV serology.²

Management of croup³

If hospital admission is not required (mild illness):

• Prescribe a single dose of oral dexamethasone (0.15 mg/kg) to be taken immediately. Glucocorticoids reduce symptoms of croup at two hours, shorten hospital stays and reduce the rate of return visits to care.⁶

• If dexamethasone is not available, oral prednisolone 1mg/kg can be used instead.⁵

• Usually, only a single dose of dexamethasone is needed. A second dose may be needed if the child continues to have problems breathing and is distressed^​​. The second dose can be given 12 hours after the first dose if the child is awake.⁵

• Antibiotics are not indicated.²

• Advise parents/carers to take the child to hospital if stridor can be heard continually, the skin between the ribs is pulling in with every breath, and/or the child is restless or agitated.

• Advise parents/carers to call an ambulance if the child:

  • Is very pale, blue, or grey (includes blue lips) for more than a few seconds.

  • Is unusually sleepy or is not responding, is having a lot of trouble breathing (eg, the belly is sinking in while breathing, or the skin between the ribs or over the windpipe is pulling in with each breath; the nostrils may also be flaring in and out).

  • Is upset (agitated or restless) while struggling to breathe and cannot be calmed down quickly.

  • Wants to sit instead of lie down, and/or if they cannot talk, are drooling, or are having trouble swallowing.

• Inpatient treatment may include inhaled adrenaline, which has been shown to reduce symptoms at 30 minutes but the effects wear off after 2 hours, and oxygen.²

• 0.2% of children require intubation.²

Self-care advice

• Use either paracetamol or ibuprofen to treat a child who is distressed due to fever.

• Antipyretic agents should not be used with the sole aim of reducing body temperature and should be continued for only as long as the child appears distressed.

• Consider changing to the other agent if the child's distress is not alleviated, but not to give both agents simultaneously, and only to alternate these agents if the distress persists, or recurs before the next dose is due.

• Don't attempt to reduce fever by under-dressing the child, or with use of tepid sponging.

• Encourage the child to take fluids regularly. For infants who are breastfed, advise continued breastfeeding.

• Check on the child regularly, including through the night.

• It is no longer advised to put the child in a steamy room or to get them to inhale steam.⁵

Complications of croup⁷

• Bacterial superinfection may result in pneumonia or bacterial tracheitis.

• Pulmonary oedema, pneumothorax, lymphadenitis and otitis media have also been reported.

• Inability to maintain adequate fluid intake may lead to dehydration.

Prognosis³

• Symptoms usually resolve within 48 hours.

• Mild croup tends to be self-limiting even without treatment, with shorter time to resolution with dexamethasone treatment.

• In most cases of moderate croup, symptoms resolve without significant complications.

• With dexamethasone and nebulised epinephrine combination treatment, the prognosis for severe croup is excellent.

• Severe upper airway obstruction can, rarely, lead to respiratory failure and arrest.

• In children with impending respiratory failure, intubation is required in 1-3% of cases.

• Death from croup is rare, occurring in about 1 in every 30,000 cases.