Croup

Epidemiology

• Commonly affects children who are aged 6 months – 3 years, but can affect those who are as young as 3 months (1)
• Peak incidence is at 2 years of age (1)

Pathophysiology

Croup is a viral upper respiratory tract infection which results in mucosal inflammation anywhere between the nose and trachea (2,5). The most common organism is the parainfluenza virus; further organisms are given in the table below (2).

The characteristic barking cough of croup is caused by the impaired movement of the vocal cords.

Risk Factors

• Being Male
  • male:female incidence ratio of 1.43:1 in <6 month children & 1.73:1 in children aged 6 to 12 months
• Autumn & Spring Season
• C/C variant of the CD14 C-159T gene has been shown by genetic studies to have a lower prevalence of croup (2).

 Clinical Features

The presenting symptoms vary according to the severity of disease which can be determined using the Westley Croup Score.

Westley Croup Score

The Westley Croup Score provides a valid scoring system that helps to categorise children based on their presenting clinical features:

Differential Diagnosis

• Epiglottitis (see table to differentiate from croup, 5)
• 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 (2)

Investigations

Diagnosis is normally a clinical decision.

For any additional tests it is important to consider the distress that these could cause the child.

Laboratory tests: FBC, CRP, U&Es

Imaging or invasive tests:

• Chest X-Ray: To identify other possible causes of symptoms including inhaled foreign bodies.
• Direct or indirect laryngoscopy is not usually performed unless the illness is atypical or another cause of airway obstruction is suspected.

Other: pulse oximetry

Risk scoring (if relevant): See mild, moderate, severe classification above

Management

Location of care

Most children with mild croup can be managed at home but consider admission in the following cases: (1)

• Previous history of severe airway obstruction
• < 6 months of age
• Immunocompromised
• Have had inadequate fluid intake
• Have had a poor response to initial treatment
• The diagnosis is uncertain
• There is significant parental anxiety

Advice to parents for home-managed patients should include: (1)

• Explaining that the symptoms usually resolve within 48 hours but may last for up to a week.
• Explaining that croup is a viral illness and antibiotics are not needed.
• Paracetamol or ibuprofen can be used to control pain and fever.
• Ensure that the child has an adequate fluid intake.
• To seek urgent medical advice if symptoms worsen e.g. the development of intermittent stridor at rest or if the child starts to have a high fever and heart rate (this could indicate a different diagnosis such as bacterial tracheitis).
• To call an ambulance if the child starts to show signs of respiratory failure.

Immediate hospital admission should occur if: (1)

• The child has moderate/severe croup or impending respiratory failure.
• You suspect a serious disorder caused by infection e.g. peritonsillar abscess, laryngeal diphtheria, or a non-infectious cause e.g. foreign body, angioneurotic oedema.

Treatment:

• For all children with croup give a single dose of oral dexamethasone (0.15mg/kg body weight) or oral prednisolone (1-2mg/kg body weight) (1).
• Nebulised adrenaline can be given to provide temporary relief of symptoms (5).
• Ensure the child is kept as calm as possible as continuing crying increases oxygen demand & causes respiratory muscle fatigue (2).
• Humidified air/steam inhalation is not advised (2).
• Oxygen Therapy as required.
• Contact ENT and an anaesthetist if there is need for airway support (5).

Complications

Complications are rare and the majority of children do not need hospitalisation. In children that are intubated the mortality rates are less than 0.5% (2)

• Lymphadenitis
• Otitis Media
• Dehydration, as a consequence of not being able to maintain fluid intake (2)
• Rare: Bacterial superinfection resulting in pneumonia or bacterial tracheitis
• Extremely rare: Pulmonary oedema, pneumothorax

Lightning Learning

Thanks to the team at www.em3.org.uk we now have a ‘Lightning Learning’ resource for you to take away.

References: