Croup

6.7 Croup

Introduction

The term croup describes an acute clinical syndrome of hoarse voice, barking cough, and inspiratory stridor usually seen in young children. Croup results from swelling of the upper airway, in and around the larynx, usually as a result of a viral infection. Croup occurs seasonally, peaking in winter months due to the epidemics of upper respiratory viruses. Parainfluenza virus type 1 accounts for around half the cases during winter, with parainfluenza type 2, influenza type A, adenoviruses, respiratory syncytial virus, enteroviruses, and possibly Mycoplasma pneumoniae causing most of the other cases. Some of the viral exanthems, such as varicella, can cause concomitant croup by involvement of the upper airway in small children. Croup is a common childhood problem, with a peak incidence of 60 per 1000 child years in those aged between 1 and 2 years, although it may be seen up to the teen years. As such, it is by far the most common cause of acute upper airways obstruction likely to present to emergency departments.

The respiratory distress caused by obstruction tends to be most marked in younger children due to the small size of their larynx, the presence of loose submucous tissues, and the tight encirclement of the subglottic area by the cricoid cartilage. In children under 8 years of age, this is the narrowest region of the airway, hence any inflammatory swelling in this area results in a significant impingement of the airway. The younger child, who has a smaller diameter airway, requires an increased vigilance to assess the degree of airway compromise.

The lower airway involvement of laryngotracheobronchitis may also cause younger children to manifest wheeze due to concurrent inflammation producing mucus in the smaller peripheral airways. Likewise, occasionally older children known to have asthma may exhibit signs of asthma in the setting of croup.¹

Presentation

History

The typical presentation of croup is in a preschool-aged child with a history of a recent onset of upper respiratory tract infection. The child subsequently develops a barking or seal-like cough, a hoarse voice and, if obstruction is severe enough, stridor. The stridor may initially be apparent only when a child is distressed, such as during crying. During crying or forced expiration the diameter of the upper airways physiologically narrows and, hence, stridor will manifest. Stridor, which is initially inspiratory, indicates obstruction at the laryngeal level or higher (i.e. upper airway). Expiratory stridor or biphasic stridor indicates more severe laryngeal obstruction or alternatively an obstruction occurring lower in the airway. The natural history of airway obstruction, when unmodified by steroids, is to increase slowly to peak over 24–48 hours. The airway compromise usually then resolves over a few days, although the laryngeal cough may persist longer.

Less common than infectious croup but usually more sudden in onset, older children may present with recurrent or spasmodic croup with no viral prodrome. This is thought to be allergic in origin. These children may have a history of atopy and suffer from asthma more than the general population. They should, however, be treated in the same manner as ‘viral’ croup. In the smaller child, particularly infants, problems with feeding, swallowing difficulties, and whether the child has been cyanosed should be ascertained.

It is important to enquire whether or not the child has had croup or other airway problems in the past and, specifically, whether the child has had any persistence of mild stridor in between acute attacks. This is important, as any child who has a pre-existing narrowing of the airway (infantile floppy larynx, laryngomalacia or other upper airway anatomical abnormalities) is more likely to proceed to severe obstruction with a superimposed acute obstruction. These children need to have a lower threshold for a period of observation as their obstruction may be more severe or persistent.

An immunisation history is important to check whether the child has had Hib vaccination if there is any suggestion that the condition could be epiglottitis; likewise, the very rare occurrence of diphtheria in the non-immunised.

Examination

Croup in children can generally be classified as mild, moderate, or severe (Table 6.7.1).

Table 6.7.1 Croup severity
Sign or symptom	Mild	Moderate or severe
Stridor	None or only if agitated	Stridor at rest
Respiratory rate	Usually normal	May be decreased
Retractions	None	+ to +++
Air entry	Normal	Normal to decreased
Colour	Normal	May be pallor
Cyanosis	None	Late sign only
Conscious state	Normal	Restless or decreased

After Marks et al 2003.²

Most children with mild croup are not distressed and have only a barking cough with no stridor at rest or stridor audible only with physical activity, crying, or agitation. Crying causes physiological narrowing of the airway and will increase the respiratory distress. Hence the distressed, crying child’s obstruction will often defervesce by allowing the child to be cuddled in the parent’s arms. There may be signs due to viral illness, such as mild fever and nasal discharge. Children with mild cases can have their throats examined, but this should be deferred in more severe cases. A compromised but functioning airway should never be made worse by upsetting the child.

In more severe cases, the child may have a more pronounced stridor at rest. As airway obstruction progresses, increased work of breathing ensues and the child exhibits increasing substernal, intercostal, and subcostal retractions. Subtle signs of hypoxia causing altered consciousness may be reflected as anxiety or restlessness in a child. An obviously fatiguing child is a worrying sign. The child manifesting decreased air entry and respiratory effort, extreme pallor, and cyanosis requires immediate intervention.

The child’s preferred position may also give clues as to severity of obstruction or to a diagnosis other than croup. Hyperextension or other abnormal positioning of the neck may suggest epiglottitis or a retropharyngeal abscess. It is unusual for the child with croup to be saliva intolerant or have any tenderness of the neck.

The use of a croup severity score may be helpful for less-experienced staff to assess children with croup and communicate findings with a colleague when seeking advice. As previously mentioned, some children may have concomitant wheeze in addition to the upper airway stridor and hence their pattern of breathing may be ‘gas trapped’ and cause hyperinflation of the chest with slow expiration phase, in contrast to those with pure croup alone.

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Tags: Textbook of Paediatric Emergency Medicine

Sep 7, 2016 | Posted by admin in EMERGENCY MEDICINE | Comments Off

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