Assessment and management of viral croup in children

Croup is an acute respiratory illness that commonly affects preschool children. Although severe episodes requiring hospital admission occur in around 5 per cent of cases, the majority of children have a mild, self-limiting illness, which can be safely managed at home. This article discusses the approach to clinical assessment and evidence-based management of childhood croup in both hospital and primary care settings.

Croup (laryngotracheobronchitis; LTB) is a common childhood illness that affects up to 6 per cent of preschool children per year,1 with a peak incidence between 18 and 24 months of age.2 Recurrence is common, and up to half of affected children will go on to have subsequent episodes during their early childhood.3,4

Croup can be caused by any of a number of respiratory tract viruses, most commonly the parainfluenza viruses types 1 and 3, which together account for over three-quarters of cases. Rare cases resulting from Mycoplasma infection have also been described. Croup typically occurs in autumn and early winter months, and biennial spikes in its incidence are seen due to epidemics of parainfluenza type 1 infection.5

The clinical features of croup result from inflammation and swelling of upper airway structures (larynx, vocal cords and trachea), and particularly from oedema affecting the narrow subglottic region. Children typically present with sudden onset of a harsh ‘barking’ cough after two to three days of a seemingly mild upper respiratory tract illness. Progressive upper airway obstruction can result in development of stridor and respiratory distress. Symptoms are usually worse at night with improvement during the daytime, but may subsequently recur the next night. Nocturnal ‘attacks’ can be abrupt in onset and dramatic in nature, leading to substantial parental anxiety. Episodes resolve within 48 hours in the majority of cases although they may last for up to one week.6

A subgroup of children with croup have recurrent, short-lived nocturnal attacks without a preceding coryzal illness. This clinical entity, termed spasmodic croup, typically affects children who are older than those with classical viral LTB. Its aetiology is not fully understood, but an overlap with atopy is recognised and a family history of similar episodes is often present. There is currently no evidence base to support an alternative course of management for spasmodic croup, and the general principles of croup management discussed later in this article should be applied.

Clinical assessment

A diagnosis of croup is made clinically on the basis of a com­patible history and examination findings – laboratory and radio­logical investigations are rarely helpful. In more severe cases of croup, investigations can actually be dangerous by causing the child to become distressed, which can result in worsening of air­ways obstruction. For this reason, a cautious approach should always be taken to the assessment of children with acute stri­dor. The child should be placed in a calm environment where they can be comforted by a parent or caregiver, and should not be repositioned from the posture they have naturally adopted as this will be one that minimises airway obstruction. Ideally, medical devices like oxygen or nebuliser masks should be held close to the child’s face by their caregiver rather than being applied tightly or administered by a healthcare professional as these actions may cause the child to become distressed.7

Key roles of the clinician in the assessment of children with croup include differentiation from other potentially serious causes of acute stridor, and assessment of clinical severity in order to guide further management. Important differences between the clinical features of croup and other conditions that cause acute stridor in this age group are summarised in Tables 1 and 2. Croup can usually be easily recognised and confidently diagnosed on the basis of a history of a barking cough that is most troublesome at night and was preceded by corzyal symp­toms, as described above.

Assessment_Croup_Table_1

Table 1. Differential diagnosis of acute stridor – infective conditions

Assessment_Croup_Table_2

Table 2. Differential diagnosis of acute stridor – noninfective conditions

Children with croup usually remain interactive and well-look­ing, in contrast to the toxic appearance of those with infections of bacterial origin such as epiglottitis and bacterial tracheitis. However, differentiation between croup and bacterial tracheitis may on occasion be particularly difficult; a high index of suspi­cion for the latter is required in children with clinical symptoms of croup associated with an unexpectedly high fever who show an inadequate response to standard croup management. Very abrupt onset of cough and stridor without a coryzal prodrome should raise suspicion of airways obstruction by an inhaled for­eign body, while a more insidious onset of stridor in the afebrile child should lead to consideration of rarer causes of noninfec­tive airways obstruction such as subglottic haemangiomata (infants) and hereditary angioedema (older children).

Congenital airway malformations such as laryngomalacia, laryngeal webs and unilateral vocal cord paralysis are far more common causes of stridor in young infants, but these aetiolo­gies usually present with a much more gradual symptom onset, which enables them to be easily distinguished from croup.

Once a diagnosis of croup has been made, the focus of assessment should turn to categorisation of disease severity. Table 3 outlines the clinical features of each severity category, and summarises management recommendations in each case. Clinicians involved in the assessment of children with croup should be aware that normal pulse oximetry should not be con­sidered reassuring, as oxygen saturation can be preserved until the late stages of airway obstruction. Indeed, if the child is given oxygen to breathe, the child may remain fully saturated but with very severe hypercapnia.

Assessment_Croup_Table_3

Table 3. Croup severity categories and recommendations for their management

Principles of croup management

The majority of croup illnesses are mild and self-limiting, and can be managed symptomatically by encouraging a good oral fluid intake and administering antipyretics as required. As croup is usually caused by viral infection, antibiotics are not routinely required and should be reserved for children with other signs suggestive of bacterial illness. Such children typically appear toxic and are sufficiently unwell that they require hospital admission, in contrast to those with viral croup, who generally remain interactive and well-looking. Similarly, there is no evidence to support the use of cough suppressants, decongestant medications or inhaled beta2 agonists.

Parental education and support is an essential component of effective management; in particular, parents should be reassured about the short and self-limiting nature of the illness, but warned that symptoms are usually worse at night and may recur after apparently having disappeared during the day. Mild croup can generally by managed at home, although hospital admission might be considered as a precautionary measure in children with risk factors for developing severe disease (see Table 4).

Assessment_Croup_Table_4

Table 4. Risk factors for severe croup

A low threshold for hospital admission should also be applied in cases of high parental anxiety, limitations in understanding or recognition of signs of illness, remoteness from hospital, or any other adverse social circumstances. Parents of children with mild croup being managed at home should be advised to seek further medical advice if the child develops symptoms suggestive of worsening airways obstruction (see Table 5).

Assessment_Croup_Table_5

Table 5. Advice for parents of children with mild croup

In cases of moderate to severe croup, the main objective of treatment is to ameliorate upper airway obstruction rapidly in order to prevent progression to respiratory failure. Administration of corticosteroids with or without nebulised adrenaline should be followed by a period of medical observation in order to confirm improvement of airway obstruction symptoms before the child is discharged home. In severe croup, there should be a low threshold for escalation of care to a high-dependency level setting if symptoms fail to rapidly improve, and particularly if repeated doses of nebulised adrenaline are required. If intravenous access is required, for example to administer steroids or fluid boluses to the seriously unwell child, an anaesthetist should be present in case critical airway obstruction develops.

Evidence-based approach to croup management

Although only 5 per cent of affected children require hospital admission,8 croup is a sufficiently common illness that this translates to a significant impact in terms of cost and healthcare resource utilisation. As a result, there is much interest in the development of new treatments that reduce the need for, or shorten the duration of, hospital admission. This section reviews the current evidence base for and against the use of various potential croup therapies that have recently been studied.

Corticosteroids

The widespread prescribing of corticosteroids for croup is thought to be responsible for the dramatic fall in hospital admission rates observed over the last three decades.9 A strong evidence base has now been established that supports administration of a corticosteroid to all children with moderate to severe croup, ie all of those with audible stridor, and arguably to any child presenting to a healthcare professional.

A 2011 Cochrane Systematic Review, which included more than 4000 children with croup, concluded that treatment with oral corticosteroids resulted in clinical improvement within six hours of administration.10 This clinical improvement translated to significantly shorter hospital admissions, a reduced likelihood of needing nebulised adrenaline and fewer return visits to healthcare professionals compared with children who did not receive corticosteroid treatment.

Steroids are usually administered orally due to ease of administration and a significantly lower treatment cost compared with nebulised budesonide. However, the nebulised and intramuscular routes have been demonstrated to be comparably effective, and should be considered in children with persistent vomiting or severe respiratory distress. Nebulised steroid treatment might also be considered in children with frequent attacks of spasmodic croup because of the risk of systemic side-effects associated with recurrent use of oral steroids.

Currently, dexamethasone and prednisolone are both commonly prescribed for croup. As there is no convincing evidence from research studies to favour either treatment, it is reasonable for selection to be determined by availability to the prescribing healthcare professional. Our recommended dose of dexamethasone is 0.15mg/kg as this has been demonstrated to be equally efficacious to 0.6mg/kg, as has a prednisolone dose of 1mg/kg.11,12 Due to the short duration of a typical episode of croup, one steroid dose is usually sufficient. However, if residual symptoms persist following the first day of treatment, it is judicious and safe to administer a second dose.

Nebulised adrenaline

Nebulised adrenaline (epinephrine) acts through a combination of bronchodilation and airway mucosal vasoconstriction, leading to a reduction in airway wall oedema. A 2013 Cochrane Systematic Review of its use in croup, which included 225 subjects, observed a temporary improvement in clinical severity within 30 minutes, which subsided by two hours postadministration. 13 It is therefore recommended for children with severe symptoms as a bridge to onset of corticosteroid action.

Racemic adrenaline (0.05ml/kg of a 2.25% solution) and L-adrenaline (0.5ml/kg of a 1:1000 solution) have been demonstrated to be comparably effective, although the L-isomer preparation may have a longer duration of action.14 Nebulised adrenaline is generally well tolerated, although cardiac monitoring is advisable when giving repeat doses because of the risk of the development of tachyarrhythmias. A theoretical risk of rebound worsening of symptoms is rarely, if ever, observed in clinical practice. In the past, it was recommended that children treated with nebulised adrenaline should routinely be admitted to hospital. However, several studies have now concurred that discharge home is safe following a three- to four-hour period of close monitoring, assuming a significant and sustained clinical improvement has been observed.15,16

Humidified air inhalation

The administration of so-called ‘mist’ therapies remains a common practice for symptomatic relief of croup, either as steam inhalation in the home setting or inhalation of humidified air via a face mask in hospital. However, a 2006 Cochrane Systematic Review that included three randomised controlled trials found no evidence that this intervention resulted in either a shortterm or sustained symptomatic improvement.17 Furthermore, several published case reports have described severe burns caused by spilling of boiling water and facial scalds from the use of steam.18 This practice is therefore not a recommended treatment for croup and should be actively discouraged.

Oxygen and mixed inspired gases

Oxygen should be administered to any child with severe airway obstruction, even in the absence of severe hypoxia, as it aids respiratory muscle function. However, when administering oxygen to a child with croup, the clinician should be mindful of the risk of masking the development of severe hypercapnia due to worsening airflow obstruction.

Heliox, an inhaled mixture of helium and oxygen gases, has been studied as a potential treatment for croup with the hypothesis that the lower density of helium compared with nitrogen in ambient air may decrease turbulence of airflow within narrowed airways. However, a 2013 Cochrane Systematic Review including almost 100 subjects found no convincing evidence that heliox resulted in any additional clinical benefit compared with the more conventional practice of co-administering oxygen and nebulised adrenaline.19

Indications for referral

Most children with croup, including the majority of those who experience recurrent attacks, do not require outpatient follow-up. However, referral to a paediatric respiratory or ENT specialist for further assessment should be considered in children with an atypical clinical course (see Table 6). In these instances, the main aim of further evaluation is to exclude an underlying structural airways abnormality, which can usually be achieved by performing flexible bronchoscopy.20

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Table 6. Indications for specialist referral

Summary

Croup is a common early childhood illness, which presents with a barking cough that is worse at night and is associated with a harsh inspiratory stridor and signs of respiratory distress in more severe cases. The illness is usually mild and self-limiting, and can be managed at home in the majority of cases, assuming that sensible safety nets have been put in place.

In each case, the management plan should be guided by symptom severity, which can be ascertained through careful clinical assessment and without the need for laboratory or radiological investigations. Oral corticosteroids have been shown to improve clinical outcomes, and should be administered to all children presenting to medical services, irrespective of disease severity. In more severe cases, nebulised adrenaline can temporarily relieve airways obstruction while the onset of steroid action is awaited. There is currently no evidence base to support the use of other interventions, including inhalation of humidified air or heliox. Although follow-up after resolution of the acute illness is not usually required, referral to a paediatric respiratory or ENT specialist should be considered in children with an atypical clinical course in order to exclude a predisposing structural airway abnormality.

Declaration of interests

None to declare.

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Assessment and management of viral croup in children

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