- Email: [email protected]
The management of acute upper airway obstruction in children
Current Paediatrics (2002) 12, 17d21 ^ 2002 Harcourt Publishers Ltd doi:10.1054/cupe.2001.0242, available online at http://www.idealibrary.com on
The management of acute upper airway obstruction in children Angela D’Amore* and Gregor Campbell HewsonR *Specialist Registrar in Paediatrics, Box 226, Addenbrooke’s Hospital, Hills Road, Cambridge CB2 2QQ, UK and RConsultant in Emergency Medicine, Box 87 Addenbrooke’s Hospital, Hills Road, Cambridge CB2 2QQ, UK KEYWORDS MeSH airway obstruction, paediatric, croup
Summary The child with upper airway obstruction is one of the most challenging emergencies in paediatric practice. Rapid assessment of the child and an understanding of the epidemiology of the condition will allow the underlying pathology and its treatment to be defined. This article reviews the most common causes of upper airway obstruction and analyses the optimal management. Viral croup is the most frequent cause of paediatric upper airway obstruction. Prompt management with nebulized adrenaline and corticosteroids avoids the need for tracheal intubation in all but a fraction of cases. Sub-glottic stenosis and bacterial tracheitis are less common problems but their management is more complex. Laryngomalacia, foreign body aspiration, mediastinal tumours and lymphadenopathy are uncommon and management is directed towards the underlying lesion. Epiglottitis has become much less prevalent since the introduction of mass immunization, but should be considered in the unvaccinated child. ^ 2002 Harcourt Publishers Ltd.
PRACTICE POINTS
INTRODUCTION
E Croup is the commonest cause of upper airway obstruction E Croup severity is best assessed clinically, there are no reliable objective measures E Prompt medical treatment usually avoids the need for tracheal intubation in croup E Corticosteroids have not been shown to have any significant adverse effects in croup E Epiglottitis is now rare in vaccinated immunocompetent children E Advanced airway management is the preserve of anaesthetists
The child’s upper airway, extending to the glottis and sub-glottic region, is particularly vulnerable to obstruction because of its narrow lumen. Flow through a tube is proportionate to the fourth power of the radius. One millimetre of upper airway oedema will cause a 16-fold increase in resistance in an infant with an airway diameter of 4 mm compared to a threefold increase in an adult with an airway diameter of 8 mm.1
RESEARCH DIRECTIONS E The effectiveness of prednisolone in comparison to dexamethasone and budesonide
Correspondence to: GCH. Tel: #01223-586879; Fax: #01223217057; E-mail: [email protected]
PHYSIOLOGY AND EPIDEMIOLOGY The presentation of airway obstruction depends on the location and degree of the lesion. Critical obstruction above the carina is fatal within minutes whereas obstruction below the bifurcation of the trachea has a less fulminant course. Inspiratory stridor is the most common clinical feature of upper airway obstruction (UAO). It results from negative intrathoracic pressure during inspiration causing the extrathoracic airways to collapse. Expiratory stridor occurs in intrathoracic airway obstruction. UAO will also increase the work of breathing, indicated by subcostal
18
CURRENT PAEDIATRICS
and sternal recession and the use of accessory muscles. End-organ hypoxia resulting in altered consciousness and cyanosis is preterminal. Viral croup is the most common cause of upper airway obstruction in children. In one series 58% of paediatric intensive care unit (PICU) admissions with UAO were due to croup. Sub-glottic stenosis, bacterial tracheitis, laryngomalacia, epiglottitis and mediastinal masses were substantially less common.2
CROUP The term croup derives from an old Scots word meaning to croak and is accepted as referring to acute laryngotracheitis or laryngo-tracheo-bronchitis. Some clinicians emphasize a distinction between infectious or ‘viral’ croup and ‘spasmodic’ croup. ‘Viral’ croup is typically but not exclusively due to parainfluenza viral infection and presents following 12}72 h of coryza with fever. ‘Spasmodic’ croup presents with a short episode of cough and stridor, typically at night without any preceding coryza. It has been reported that 40% of admissions with croup have features of both viral (fever, rhinorrhoea) and spasmodic (atopy, recurrence) croup. It is likely that these two presentations are opposite ends of a single spectrum of illness.3 Croup is common with a peak incidence of 60 per 1000 child-years in the population aged between 1 and 2 years. It is generally benign and self-limiting. The typical clinical features are hoarseness, a barking cough, stridor and a low-grade fever. Features suggesting an alternative diagnosis are summarized in Table 1. Most cases are observed at home with or without medical supervision. A small proportion attend hospital, with between 1.5 and 15% of these children requiring admission. The intubation rate for children hospitalized with croup was between 1 and 5% prior to the introduction of steroid therapy.3 In most children, croup runs a mild 3-day course, becoming more severe at night and settling during the day. The severity of an episode of croup is best assessed on clinical grounds. Stridor at rest, increased work of breathing at rest and decreased air entry indicate more severe disease. The ‘Croup scores’ are subjective and
Table 1 Caution in diagnosing croup Feature
Alternative diagnosis
Less than 4 months High fever Peripheral cavernous haemangiomas Post-neonatal ICU infant
Congenital airway abnormality Bacterial tracheitis/epiglottitis Sub-glottic haemangioma Sub-glottic stenosis
principally used as research tools. It is helpful to classify children with croup as those suitable for reassurance and discharge, those that can be treated and discharged and those that require admission and/or intensive therapy.
MEDICAL TREATMENT Humidification The only randomized trial of humidification suggested that this therapy was ineffectual.4 The perceived improvement probably relates to the reassuring presence of a carer in a warm, light environment. There is little reason to discourage the domestic use of the ‘steamy bathroom’ provided it is recognized as a placebo effect. Parents should be advised to run the taps with the plug out and avoid boiled kettles to decrease the risk of scalds. There is no evidence to support humidification therapy in a hospital setting. Nebulized saline has been used as a placebo in randomized controlled trials of steroids or adrenaline and does not have any sustained effects.
Adrenaline Nebulized adrenaline became the mainstay of severe croup management after work by Westley showed that racemic epinephrine had clear benefits over nebulized saline.5 The mode of action of adrenaline is believed to be alpha-receptor-mediated vasoconstriction resulting in decreased mucosal oedema. The initial work on the use of adrenaline in croup focused on racemic epinephrine. This preparation contains equal amounts of L and D isomers and was chosen over L-adrenaline on the pharmacological grounds that there would be fewer cardiovascular effects. Much of the subsequent literature also described the use of racemic epinephrine despite this preparation only being available in major paediatric centres in the United States of America. L-Adrenaline, the most widely available preparation, has since been shown to be a safe and effective alternative to racemic epinephrine.6 The standard dose of nebulized adrenaline is 5 ml of 1 in 1000 preparation. Circumoral pallor and tachycardia are to be expected. No serious side-effects have been documented. The duration of action of nebulized adrenaline is between 20 min and 3 h. Some reports have emphasized a rebound phenomenon after treatment with nebulized adrenaline. ‘Rebound’ is misleading as the deterioration is a waning of the therapeutic effects and involves at worst a return to the pretreatment baseline. It was common practice, before the use of steroids, to admit any child who had been treated with nebulized adrenaline. This may not be necessary if steroids are
THE MANAGEMENT OF ACUTE UPPER AIRWAY OBSTRUCTION IN CHILDREN administered immediately after nebulized adrenaline since the two treatments will overlap. A child with mild or moderate croup who has received steroid treatment after nebulized adrenaline and who has been observed for 3 h without relapse may be discharged safely.7
19
severe disease. The final choice of agent will depend on compliance with mode of delivery, local availability and cost. It is debatable whether children with mild disease should be treated with corticosteroids as most mild croup is benign and self-limiting.
INTUBATION Steroids Corticosteroids were first advocated for viral croup in the 1950s. Although a succession of trials conducted over the next 30 years failed to show any clear benefit, a systematic review by Kairys8 concluded that there was benefit. More recently, a Cochrane review concluded that steroid use improves clinical parameters, decreases the duration of hospital stay and the need for rescue nebulized adrenaline.9 Steroids have a more rapid therapeutic onset in croup than in asthma, possibly due to a vasoconstrictor effect, with most children showing a prompt and sustained improvement within 2 h. Steroids do not affect the duration of the viral symptoms of cough, rhinorrhea and sore throat. There is minimal evidence of adverse effects of steroid use in croup. Severe varicella infections and bacterial tracheitis are theoretical complications but have not been shown to be practical problems. Steroids have been shown to improve clinical status, decrease time spent in A&E, decrease return visits and decrease admission rates. Dexamethasone and nebulized budesonide have been shown to be equally effective in treating children with mild, moderate and severe croup. Dexamethasone has been the most extensively studied treatment with doses ranging between 0.15 and 0.6 mg/kg. The majority of studies showing clear benefit from dexamethasone have used a dosage of 0.6 mg/kg.9 Some advocate a lower dose of 0.15 mg/kg.10 This lower dose has been shown to be effective in decreasing hospital re-attendance in children with mild croup. Nebulized budesonide has been studied as a croup treatment at a dosage of 2 mg. A single dose is usually adequate for moderate croup and relapse is uncommon. A study comparing dexamethasone (0.6 mg/kg) to budesonide (2 mg) did not demonstrate any difference in outcome.11 Intramuscular dexamethasone (0.6 mg/kg) has been shown to be superior to nebulized budesonide (2 mg).12 Studies comparing nebulized budesonide and oral dexamethasone have not shown any appreciable difference in speed of onset. Prednisolone, the most commonly used oral corticosteroid, has not been studied extensively in croup but there is little reason to doubt that it is effective in an equivalent dosage (1}2 mg/kg). Oral dexamethasone is widely available, easy to administer and cheap. In the absence of convincing evidence, it seems prudent to use the established dose of 0.6 mg/kg of dexamethasone in a child with moderate or
A small proportion of children will require tracheal intubation for croup. It is difficult to offer objective criteria, as the decision to intubate is not related to any specific parameter. The decision to intubate is based on progressively worsening obstruction or impending exhaustion from increased work of breathing. There is usually time to assess the child’s response to treatment. One series reported that only four out of the 25 children that required intubation did so within 1 h of arrival at hospital.2 Intubation is rarely necessary if adequate doses of steroids and adrenaline have been given promptly. The most common technique is gaseous induction followed by nasotracheal intubation. It is common practice to use a smaller tube (a size or half size smaller than calculated for age) because of the swollen glottis, sub-glottis and trachea. The aim is to establish an adequate rather than a maximal airway.
Intensive therapy unit management Children intubated for croup and other forms of subglottic obstruction are treated empirically with oral prednisolone until successful extubation. Extubation is usually planned around the 5th day on empirical grounds or slightly earlier if a leak develops. The presence of thick secretions generally delays extubation. If extubation is unsuccessful, the severity of the disease should be assessed fibro-endoscopically.
Sub-glottic stenosis The sub-glottic region, extending from below the true cords to the lower cricoid cartilage is the narrowest part of the upper airway and is vulnerable to injury and subsequent narrowing. Acquired sub-glottic stenosis is closely related to tracheal intubation and is commoner than the congenital form. The endotracheal tube causes ischaemic necrosis by pressure at the level of the cricoid. This may occur even if an appropriate-sized tube is used as the size of the cricoid varies between children. Movement of the tube causing mucosal friction has also been implicated. The duration of intubation does not seem to be directly related to the subsequent development of sub-glottic stenosis. Acquired sub-glottic stenosis is becoming less common due to changes in neonatal airway and ventilation techniques.
20 Mild to moderate sub-glottic stenosis may only present when viral upper respiratory tract infection results in further narrowing and causes respiratory distress. Infants who have been intubated as neonates should be treated with extreme caution if they present with stridor. These children may prove to have difficult airways and require prolonged intubation.
Laryngomalacia Laryngomalacia is the most common cause of stridor in the first few weeks of life. Stridor is usually present from birth but may develop up to 3 months after birth and may only be apparent during viral infections. The symptoms are usually intermittent and tend to be worse when the baby is supine. Intubation may be required for acute or chronic obstruction. Laryngomalacia may cause feeding difficulties because of dyspnoea. Surgical treatment (aryepiglottoplasty) is only indicated if there is failure to thrive. The floppy epiglottis, large redundant aryepiglottic folds or large arytenoid processes are best defined fibro-endoscopically. The anatomical features resolve at 1}2 years as the airway cartilage hardens. Laryngomalacia is generally benign and self-limiting although disturbed parental sleep because of noisy nocturnal breathing is a common complaint.
Foreign body aspiration The death rate from foreign body aspiration (FBA) in childhood has fallen in recent years because of legislation and increased public awareness. Ninety per cent of aspirated foreign bodies are food material with peanuts being the most common offender.13 ‘Lego’ block aspiration has occurred frequently enough for the manufacturers to have considered adding barium. The most common place of lodgement has been shown to be the right main bronchus (41.5%), only 17% lodged in the larynx or trachea.13 The onset of coughing while eating or playing with small toys suggests FBA but clinical presentation depends on the site of lodgement and the degree of obstruction caused. Presentation is often sub-acute, 2 or 3 days after the choking. Critical obstruction of a major airway will rapidly cause asphyxia. Although there are established guidelines for management of the choking child it is crucial to differentiate between the partially obstructed child who is maintaining an airway and complete obstruction.14 Most aspirated objects are small enough to pass through the larynx and trachea. Wheeze is the most prominent symptom if a mainstem bronchus is involved, blockage of segmental airway usually produces chronic cough. It would be unusual for FBA to be mistaken for croup but a lower airway FBA
CURRENT PAEDIATRICS may mimic asthma. Foreign body aspiration should be considered with any unexplained pulmonary abnormality.
Epiglottitis The child’s epiglottis has loose mucosa on the lingual surface. This is prone to severe oedema causing supraglottic obstruction. The presentation of epiglottitis (dysphagia, dysphonia, dyspnoea and droolingethe 4Ds) is well recognized. Stridor is uncommon in epiglottitis because the obstruction is supraglottic. Paediatric epiglottitis is usually caused by invasive Haemophilus influenza B (Hib). There was a precipitate drop in childhood epiglottitis after the introduction of the Hib vaccine to the UK in 1992. The vaccine has been estimated to be 99% effective in children who receive three doses in infancy.15 Data from the British Paediatric Surveillance Unit have shown that there has been an average of three cases of epiglottitis annually in children who have received three doses of Hib in infancy (true vaccine failures). Approximately, one-third of vaccine failures are associated with conditions such as prematurity or immunocompromise.15 Childhood epiglottitis is now less common than the adult form. A child presenting unwell with high fever and upper airway obstruction should have epiglottitis considered but bacterial tracheitis is now a more likely diagnosis except in unvaccinated children.
Bacterial tracheitis Bacterial tracheitis tends to affect older children and presents with a short history of high fever and severe stridor. Staphylococcus aureus is the commonest pathogen. These children usually require intubation in addition to intravenous antibiotics. Nebulized adrenaline has no value. The disease often runs a complicated course. Diagnosis is confirmed by culture of the copious, purulent tracheal secretions.
SUMMARY The likely cause of UAO in a child can usually be discerned from a rapid clinical assessment. Viral croup is the most common diagnosis. Early treatment with nebulized adrenaline and steroids should avoid the need for intubation. Croup should be diagnosed cautiously in a child who has been previously intubated or is less than 4 months old. Drooling and high fever suggest bacterial tracheitis or epiglottitis although the latter has become very rare in immunized children. Steroids and adrenaline are ineffective in these conditions. Laryngomalacia is the most likely cause of stridor in the first 3 months of life. Other congenital obstructions, such as haemangiomas and vascular webs should also be considered.
THE MANAGEMENT OF ACUTE UPPER AIRWAY OBSTRUCTION IN CHILDREN Foreign body aspiration has multiple modes of presentation. The current choking guidelines offer an approach to critical foreign body airway obstruction. Critical airway obstruction requires a definitive airway. This should be the preserve of an anaesthetist with paediatric skills, supported by an ENT surgeon. Inhalational induction of anaesthesia, followed by laryngoscopy and intubation, is the safest technique. A child who is maintaining an airway despite partial obstruction should be left undisturbed and closely observed pending the arrival of expert help.
ACKNOWLEDGEMENT The contents of this review were initially presented at a joint symposium of the Royal College of Physicians of Edinburgh and the Royal College of Paediatrics and Child Health.
REFERENCES 1. Cote C J, Todres I D. The paediatric airway. In: Cote C J, Ryan J F et al. (eds). A practice of anaesthesia for infants and children 2nd Edn, Philadelphia, PA: WB Saunders 1993, pp. 55}80. 2. Durward A D, Nicoll S J B, Oliver J, Tibby S M, Murdoch I A. The outcome of patients with upper airway obstruction transported to a regional paediatric intensive care unit. Eur J Pediatr 1998; 157: 907}911. 3. Skolnik N S. Treatment of croup a critical review. Am J Dis Child 1989; 143: 1045}1049. 4. Bourchier D, Dawson K P, Fergusson D M. Humidification in viral croup: a controlled trial. Aust Paediatr J 1984; 20: 289}291.
21
5. Westley C R, Cotton E K, Brooks M D. Nebulised racemic epinephrine by IPPB for the treatment of croup, a double blind study. Am J Dis Child 1978; 132: 484}487. 6. Waisman Y, Klein B L, Boenning D A et al. Prospective randomised double-blind study comparing L-epinephrine and racemic epinephrine aerosols in the treatment of laryngotracheitis (croup). Pediatrics 1992; 89(2): 302}306. 7. Ledwith C A, Shea L M, Mauro R D. Safety and efficacy of nebulized racemic epinephrine in conjunction with oral dexamethasone and mist in the outpatient treatment of croup. Ann Emerg Med 1995; 25.3: 331}337. 8. Kairys S W, Olmstead EM, O’Connor G T. Steroid treatment of laryngotracheitis: a meta-analysis of the evidence form randomised trials. Pediatrics 1989; 83: 683}693. 9. Ausejo M, Saenz A, Pham B et al. Glucocorticoids for croup (Cochrane review). In: The Cochrane Library 2, Oxford Update Software, 2001. 10. Geelhoed G C, MacDonald W B. Oral dexamethasone in the treatment of croup: 0.15 mg/kg versus 0.3 mg/kg versus 0.6 mg/g. Pediatr Pulmonol 1995; 20 (6): 326}328. 11. KlassenT P, Craig W R, Moher D. Nebulised budesonide and oral dexamethasone for treatment of croup. A randomised controlled trial. JAMA 1998; 279(20): 1629}1632. 12. Johnson D W, Jacobson S, Edney P C, Hadfield P, Mundy M E, Schuh S. A comparison of nebulised budesonide, intramuscular dexamethasone and placebo for moderately severe croup. N Engl J Med 1998; 339(8): 498}503. 13. Blazer S, Naveh Y, Friedman A. Foreign body in the airway, a review of 200 cases Am J Dis Child 1980; 134: 68}71. 14. The American Heart Association in collaboration with the International Committee on Resuscitation (ILCOR) Guidelines 2000 for Cardiopulmonary resuscitation and Emergency Cardiovascular Care. An international consensus on science. Resuscitation 2000; 301}341. 15. The Royal College of Paediatrics and Child Health, British Paediatric Surveillance Unit Annual Report 1998-99: 29}31.
The management of acute upper airway obstruction in children Angela D’Amore* and Gregor Campbell HewsonR *Specialist Registrar in Paediatrics, Box 226, Addenbrooke’s Hospital, Hills Road, Cambridge CB2 2QQ, UK and RConsultant in Emergency Medicine, Box 87 Addenbrooke’s Hospital, Hills Road, Cambridge CB2 2QQ, UK KEYWORDS MeSH airway obstruction, paediatric, croup
Summary The child with upper airway obstruction is one of the most challenging emergencies in paediatric practice. Rapid assessment of the child and an understanding of the epidemiology of the condition will allow the underlying pathology and its treatment to be defined. This article reviews the most common causes of upper airway obstruction and analyses the optimal management. Viral croup is the most frequent cause of paediatric upper airway obstruction. Prompt management with nebulized adrenaline and corticosteroids avoids the need for tracheal intubation in all but a fraction of cases. Sub-glottic stenosis and bacterial tracheitis are less common problems but their management is more complex. Laryngomalacia, foreign body aspiration, mediastinal tumours and lymphadenopathy are uncommon and management is directed towards the underlying lesion. Epiglottitis has become much less prevalent since the introduction of mass immunization, but should be considered in the unvaccinated child. ^ 2002 Harcourt Publishers Ltd.
PRACTICE POINTS
INTRODUCTION
E Croup is the commonest cause of upper airway obstruction E Croup severity is best assessed clinically, there are no reliable objective measures E Prompt medical treatment usually avoids the need for tracheal intubation in croup E Corticosteroids have not been shown to have any significant adverse effects in croup E Epiglottitis is now rare in vaccinated immunocompetent children E Advanced airway management is the preserve of anaesthetists
The child’s upper airway, extending to the glottis and sub-glottic region, is particularly vulnerable to obstruction because of its narrow lumen. Flow through a tube is proportionate to the fourth power of the radius. One millimetre of upper airway oedema will cause a 16-fold increase in resistance in an infant with an airway diameter of 4 mm compared to a threefold increase in an adult with an airway diameter of 8 mm.1
RESEARCH DIRECTIONS E The effectiveness of prednisolone in comparison to dexamethasone and budesonide
Correspondence to: GCH. Tel: #01223-586879; Fax: #01223217057; E-mail: [email protected]
PHYSIOLOGY AND EPIDEMIOLOGY The presentation of airway obstruction depends on the location and degree of the lesion. Critical obstruction above the carina is fatal within minutes whereas obstruction below the bifurcation of the trachea has a less fulminant course. Inspiratory stridor is the most common clinical feature of upper airway obstruction (UAO). It results from negative intrathoracic pressure during inspiration causing the extrathoracic airways to collapse. Expiratory stridor occurs in intrathoracic airway obstruction. UAO will also increase the work of breathing, indicated by subcostal
18
CURRENT PAEDIATRICS
and sternal recession and the use of accessory muscles. End-organ hypoxia resulting in altered consciousness and cyanosis is preterminal. Viral croup is the most common cause of upper airway obstruction in children. In one series 58% of paediatric intensive care unit (PICU) admissions with UAO were due to croup. Sub-glottic stenosis, bacterial tracheitis, laryngomalacia, epiglottitis and mediastinal masses were substantially less common.2
CROUP The term croup derives from an old Scots word meaning to croak and is accepted as referring to acute laryngotracheitis or laryngo-tracheo-bronchitis. Some clinicians emphasize a distinction between infectious or ‘viral’ croup and ‘spasmodic’ croup. ‘Viral’ croup is typically but not exclusively due to parainfluenza viral infection and presents following 12}72 h of coryza with fever. ‘Spasmodic’ croup presents with a short episode of cough and stridor, typically at night without any preceding coryza. It has been reported that 40% of admissions with croup have features of both viral (fever, rhinorrhoea) and spasmodic (atopy, recurrence) croup. It is likely that these two presentations are opposite ends of a single spectrum of illness.3 Croup is common with a peak incidence of 60 per 1000 child-years in the population aged between 1 and 2 years. It is generally benign and self-limiting. The typical clinical features are hoarseness, a barking cough, stridor and a low-grade fever. Features suggesting an alternative diagnosis are summarized in Table 1. Most cases are observed at home with or without medical supervision. A small proportion attend hospital, with between 1.5 and 15% of these children requiring admission. The intubation rate for children hospitalized with croup was between 1 and 5% prior to the introduction of steroid therapy.3 In most children, croup runs a mild 3-day course, becoming more severe at night and settling during the day. The severity of an episode of croup is best assessed on clinical grounds. Stridor at rest, increased work of breathing at rest and decreased air entry indicate more severe disease. The ‘Croup scores’ are subjective and
Table 1 Caution in diagnosing croup Feature
Alternative diagnosis
Less than 4 months High fever Peripheral cavernous haemangiomas Post-neonatal ICU infant
Congenital airway abnormality Bacterial tracheitis/epiglottitis Sub-glottic haemangioma Sub-glottic stenosis
principally used as research tools. It is helpful to classify children with croup as those suitable for reassurance and discharge, those that can be treated and discharged and those that require admission and/or intensive therapy.
MEDICAL TREATMENT Humidification The only randomized trial of humidification suggested that this therapy was ineffectual.4 The perceived improvement probably relates to the reassuring presence of a carer in a warm, light environment. There is little reason to discourage the domestic use of the ‘steamy bathroom’ provided it is recognized as a placebo effect. Parents should be advised to run the taps with the plug out and avoid boiled kettles to decrease the risk of scalds. There is no evidence to support humidification therapy in a hospital setting. Nebulized saline has been used as a placebo in randomized controlled trials of steroids or adrenaline and does not have any sustained effects.
Adrenaline Nebulized adrenaline became the mainstay of severe croup management after work by Westley showed that racemic epinephrine had clear benefits over nebulized saline.5 The mode of action of adrenaline is believed to be alpha-receptor-mediated vasoconstriction resulting in decreased mucosal oedema. The initial work on the use of adrenaline in croup focused on racemic epinephrine. This preparation contains equal amounts of L and D isomers and was chosen over L-adrenaline on the pharmacological grounds that there would be fewer cardiovascular effects. Much of the subsequent literature also described the use of racemic epinephrine despite this preparation only being available in major paediatric centres in the United States of America. L-Adrenaline, the most widely available preparation, has since been shown to be a safe and effective alternative to racemic epinephrine.6 The standard dose of nebulized adrenaline is 5 ml of 1 in 1000 preparation. Circumoral pallor and tachycardia are to be expected. No serious side-effects have been documented. The duration of action of nebulized adrenaline is between 20 min and 3 h. Some reports have emphasized a rebound phenomenon after treatment with nebulized adrenaline. ‘Rebound’ is misleading as the deterioration is a waning of the therapeutic effects and involves at worst a return to the pretreatment baseline. It was common practice, before the use of steroids, to admit any child who had been treated with nebulized adrenaline. This may not be necessary if steroids are
THE MANAGEMENT OF ACUTE UPPER AIRWAY OBSTRUCTION IN CHILDREN administered immediately after nebulized adrenaline since the two treatments will overlap. A child with mild or moderate croup who has received steroid treatment after nebulized adrenaline and who has been observed for 3 h without relapse may be discharged safely.7
19
severe disease. The final choice of agent will depend on compliance with mode of delivery, local availability and cost. It is debatable whether children with mild disease should be treated with corticosteroids as most mild croup is benign and self-limiting.
INTUBATION Steroids Corticosteroids were first advocated for viral croup in the 1950s. Although a succession of trials conducted over the next 30 years failed to show any clear benefit, a systematic review by Kairys8 concluded that there was benefit. More recently, a Cochrane review concluded that steroid use improves clinical parameters, decreases the duration of hospital stay and the need for rescue nebulized adrenaline.9 Steroids have a more rapid therapeutic onset in croup than in asthma, possibly due to a vasoconstrictor effect, with most children showing a prompt and sustained improvement within 2 h. Steroids do not affect the duration of the viral symptoms of cough, rhinorrhea and sore throat. There is minimal evidence of adverse effects of steroid use in croup. Severe varicella infections and bacterial tracheitis are theoretical complications but have not been shown to be practical problems. Steroids have been shown to improve clinical status, decrease time spent in A&E, decrease return visits and decrease admission rates. Dexamethasone and nebulized budesonide have been shown to be equally effective in treating children with mild, moderate and severe croup. Dexamethasone has been the most extensively studied treatment with doses ranging between 0.15 and 0.6 mg/kg. The majority of studies showing clear benefit from dexamethasone have used a dosage of 0.6 mg/kg.9 Some advocate a lower dose of 0.15 mg/kg.10 This lower dose has been shown to be effective in decreasing hospital re-attendance in children with mild croup. Nebulized budesonide has been studied as a croup treatment at a dosage of 2 mg. A single dose is usually adequate for moderate croup and relapse is uncommon. A study comparing dexamethasone (0.6 mg/kg) to budesonide (2 mg) did not demonstrate any difference in outcome.11 Intramuscular dexamethasone (0.6 mg/kg) has been shown to be superior to nebulized budesonide (2 mg).12 Studies comparing nebulized budesonide and oral dexamethasone have not shown any appreciable difference in speed of onset. Prednisolone, the most commonly used oral corticosteroid, has not been studied extensively in croup but there is little reason to doubt that it is effective in an equivalent dosage (1}2 mg/kg). Oral dexamethasone is widely available, easy to administer and cheap. In the absence of convincing evidence, it seems prudent to use the established dose of 0.6 mg/kg of dexamethasone in a child with moderate or
A small proportion of children will require tracheal intubation for croup. It is difficult to offer objective criteria, as the decision to intubate is not related to any specific parameter. The decision to intubate is based on progressively worsening obstruction or impending exhaustion from increased work of breathing. There is usually time to assess the child’s response to treatment. One series reported that only four out of the 25 children that required intubation did so within 1 h of arrival at hospital.2 Intubation is rarely necessary if adequate doses of steroids and adrenaline have been given promptly. The most common technique is gaseous induction followed by nasotracheal intubation. It is common practice to use a smaller tube (a size or half size smaller than calculated for age) because of the swollen glottis, sub-glottis and trachea. The aim is to establish an adequate rather than a maximal airway.
Intensive therapy unit management Children intubated for croup and other forms of subglottic obstruction are treated empirically with oral prednisolone until successful extubation. Extubation is usually planned around the 5th day on empirical grounds or slightly earlier if a leak develops. The presence of thick secretions generally delays extubation. If extubation is unsuccessful, the severity of the disease should be assessed fibro-endoscopically.
Sub-glottic stenosis The sub-glottic region, extending from below the true cords to the lower cricoid cartilage is the narrowest part of the upper airway and is vulnerable to injury and subsequent narrowing. Acquired sub-glottic stenosis is closely related to tracheal intubation and is commoner than the congenital form. The endotracheal tube causes ischaemic necrosis by pressure at the level of the cricoid. This may occur even if an appropriate-sized tube is used as the size of the cricoid varies between children. Movement of the tube causing mucosal friction has also been implicated. The duration of intubation does not seem to be directly related to the subsequent development of sub-glottic stenosis. Acquired sub-glottic stenosis is becoming less common due to changes in neonatal airway and ventilation techniques.
20 Mild to moderate sub-glottic stenosis may only present when viral upper respiratory tract infection results in further narrowing and causes respiratory distress. Infants who have been intubated as neonates should be treated with extreme caution if they present with stridor. These children may prove to have difficult airways and require prolonged intubation.
Laryngomalacia Laryngomalacia is the most common cause of stridor in the first few weeks of life. Stridor is usually present from birth but may develop up to 3 months after birth and may only be apparent during viral infections. The symptoms are usually intermittent and tend to be worse when the baby is supine. Intubation may be required for acute or chronic obstruction. Laryngomalacia may cause feeding difficulties because of dyspnoea. Surgical treatment (aryepiglottoplasty) is only indicated if there is failure to thrive. The floppy epiglottis, large redundant aryepiglottic folds or large arytenoid processes are best defined fibro-endoscopically. The anatomical features resolve at 1}2 years as the airway cartilage hardens. Laryngomalacia is generally benign and self-limiting although disturbed parental sleep because of noisy nocturnal breathing is a common complaint.
Foreign body aspiration The death rate from foreign body aspiration (FBA) in childhood has fallen in recent years because of legislation and increased public awareness. Ninety per cent of aspirated foreign bodies are food material with peanuts being the most common offender.13 ‘Lego’ block aspiration has occurred frequently enough for the manufacturers to have considered adding barium. The most common place of lodgement has been shown to be the right main bronchus (41.5%), only 17% lodged in the larynx or trachea.13 The onset of coughing while eating or playing with small toys suggests FBA but clinical presentation depends on the site of lodgement and the degree of obstruction caused. Presentation is often sub-acute, 2 or 3 days after the choking. Critical obstruction of a major airway will rapidly cause asphyxia. Although there are established guidelines for management of the choking child it is crucial to differentiate between the partially obstructed child who is maintaining an airway and complete obstruction.14 Most aspirated objects are small enough to pass through the larynx and trachea. Wheeze is the most prominent symptom if a mainstem bronchus is involved, blockage of segmental airway usually produces chronic cough. It would be unusual for FBA to be mistaken for croup but a lower airway FBA
CURRENT PAEDIATRICS may mimic asthma. Foreign body aspiration should be considered with any unexplained pulmonary abnormality.
Epiglottitis The child’s epiglottis has loose mucosa on the lingual surface. This is prone to severe oedema causing supraglottic obstruction. The presentation of epiglottitis (dysphagia, dysphonia, dyspnoea and droolingethe 4Ds) is well recognized. Stridor is uncommon in epiglottitis because the obstruction is supraglottic. Paediatric epiglottitis is usually caused by invasive Haemophilus influenza B (Hib). There was a precipitate drop in childhood epiglottitis after the introduction of the Hib vaccine to the UK in 1992. The vaccine has been estimated to be 99% effective in children who receive three doses in infancy.15 Data from the British Paediatric Surveillance Unit have shown that there has been an average of three cases of epiglottitis annually in children who have received three doses of Hib in infancy (true vaccine failures). Approximately, one-third of vaccine failures are associated with conditions such as prematurity or immunocompromise.15 Childhood epiglottitis is now less common than the adult form. A child presenting unwell with high fever and upper airway obstruction should have epiglottitis considered but bacterial tracheitis is now a more likely diagnosis except in unvaccinated children.
Bacterial tracheitis Bacterial tracheitis tends to affect older children and presents with a short history of high fever and severe stridor. Staphylococcus aureus is the commonest pathogen. These children usually require intubation in addition to intravenous antibiotics. Nebulized adrenaline has no value. The disease often runs a complicated course. Diagnosis is confirmed by culture of the copious, purulent tracheal secretions.
SUMMARY The likely cause of UAO in a child can usually be discerned from a rapid clinical assessment. Viral croup is the most common diagnosis. Early treatment with nebulized adrenaline and steroids should avoid the need for intubation. Croup should be diagnosed cautiously in a child who has been previously intubated or is less than 4 months old. Drooling and high fever suggest bacterial tracheitis or epiglottitis although the latter has become very rare in immunized children. Steroids and adrenaline are ineffective in these conditions. Laryngomalacia is the most likely cause of stridor in the first 3 months of life. Other congenital obstructions, such as haemangiomas and vascular webs should also be considered.
THE MANAGEMENT OF ACUTE UPPER AIRWAY OBSTRUCTION IN CHILDREN Foreign body aspiration has multiple modes of presentation. The current choking guidelines offer an approach to critical foreign body airway obstruction. Critical airway obstruction requires a definitive airway. This should be the preserve of an anaesthetist with paediatric skills, supported by an ENT surgeon. Inhalational induction of anaesthesia, followed by laryngoscopy and intubation, is the safest technique. A child who is maintaining an airway despite partial obstruction should be left undisturbed and closely observed pending the arrival of expert help.
ACKNOWLEDGEMENT The contents of this review were initially presented at a joint symposium of the Royal College of Physicians of Edinburgh and the Royal College of Paediatrics and Child Health.
REFERENCES 1. Cote C J, Todres I D. The paediatric airway. In: Cote C J, Ryan J F et al. (eds). A practice of anaesthesia for infants and children 2nd Edn, Philadelphia, PA: WB Saunders 1993, pp. 55}80. 2. Durward A D, Nicoll S J B, Oliver J, Tibby S M, Murdoch I A. The outcome of patients with upper airway obstruction transported to a regional paediatric intensive care unit. Eur J Pediatr 1998; 157: 907}911. 3. Skolnik N S. Treatment of croup a critical review. Am J Dis Child 1989; 143: 1045}1049. 4. Bourchier D, Dawson K P, Fergusson D M. Humidification in viral croup: a controlled trial. Aust Paediatr J 1984; 20: 289}291.
21
5. Westley C R, Cotton E K, Brooks M D. Nebulised racemic epinephrine by IPPB for the treatment of croup, a double blind study. Am J Dis Child 1978; 132: 484}487. 6. Waisman Y, Klein B L, Boenning D A et al. Prospective randomised double-blind study comparing L-epinephrine and racemic epinephrine aerosols in the treatment of laryngotracheitis (croup). Pediatrics 1992; 89(2): 302}306. 7. Ledwith C A, Shea L M, Mauro R D. Safety and efficacy of nebulized racemic epinephrine in conjunction with oral dexamethasone and mist in the outpatient treatment of croup. Ann Emerg Med 1995; 25.3: 331}337. 8. Kairys S W, Olmstead EM, O’Connor G T. Steroid treatment of laryngotracheitis: a meta-analysis of the evidence form randomised trials. Pediatrics 1989; 83: 683}693. 9. Ausejo M, Saenz A, Pham B et al. Glucocorticoids for croup (Cochrane review). In: The Cochrane Library 2, Oxford Update Software, 2001. 10. Geelhoed G C, MacDonald W B. Oral dexamethasone in the treatment of croup: 0.15 mg/kg versus 0.3 mg/kg versus 0.6 mg/g. Pediatr Pulmonol 1995; 20 (6): 326}328. 11. KlassenT P, Craig W R, Moher D. Nebulised budesonide and oral dexamethasone for treatment of croup. A randomised controlled trial. JAMA 1998; 279(20): 1629}1632. 12. Johnson D W, Jacobson S, Edney P C, Hadfield P, Mundy M E, Schuh S. A comparison of nebulised budesonide, intramuscular dexamethasone and placebo for moderately severe croup. N Engl J Med 1998; 339(8): 498}503. 13. Blazer S, Naveh Y, Friedman A. Foreign body in the airway, a review of 200 cases Am J Dis Child 1980; 134: 68}71. 14. The American Heart Association in collaboration with the International Committee on Resuscitation (ILCOR) Guidelines 2000 for Cardiopulmonary resuscitation and Emergency Cardiovascular Care. An international consensus on science. Resuscitation 2000; 301}341. 15. The Royal College of Paediatrics and Child Health, British Paediatric Surveillance Unit Annual Report 1998-99: 29}31.