Which of the following is/are commonly seen on the lateral neck x-ray of a patient with ltb?

What Not To Do:

Discussion

Laryngotracheobronchitis or viral croup is the most common infectious cause of acute upper airway obstruction in children. Most cases occur in the late fall and early spring. Parainfluenza viruses cause most cases of croup. Other responsible viruses include influenza A and B, adenovirus, respiratory syncytial virus, and rhinovirus. The viral infection leads to inflammation of the nasopharynx and subglottic area of the upper airway.

Stridor in children with croup occurs from the mucosal and submucosal edema of this subglottic portion of the airway, which is the narrowest portion of a child's upper airway.

Not all children with stridor have croup. Excluding other causes, especially foreign body aspirations or ingestions, is crucial.

In contrast with viral croup, a nonseasonal allergic variant known as spasmodic croup may occur. This disorder typically has an abrupt onset, with no preceding upper respiratory infection and no fever. Spasmodic croup usually resolves quickly with exposure to humidified air, only to recur for the next few days.

When high fever, toxicity, and worsening respiratory distress develop after several days of croup-like illness, consider the possibility of the more serious but uncommon diagnosis of bacterial tracheitis.

ACUTE LARYNGOTRACHEOBRONCHITIS AND LARYNGOTRACHEOBRONCHOPNEUMONITIS (BACTERIAL TRACHEITIS)

Laryngotracheobronchitis and laryngotracheobronchopneumonitis are far less common occurrences than are laryngotracheitis and spasmodic croup; however, these illnesses occur more commonly than generally realized.* These entities may be considered an extension of acute laryngotracheitis, as numerous descriptions in the literature suggest.* The severity of the illness is due to secondary bacterial infection. Initial symptoms and signs are similar to those of laryngotracheitis (see Table 22-4). An afflicted child usually has mild to moderately severe illness for 2 to 7 days and then suddenly becomes markedly worse. Occasionally, upper and lower airway obstructions seem to occur simultaneously. In many children, the distress from tracheal obstruction is of such magnitude that the symptoms and signs of lower respiratory involvement go unnoticed. Symptoms and signs associated with extension of disease to the bronchi, bronchioles, and lung substance include rales, air trapping, wheezing, and a further increase in the respiratory rate. Obstruction in these illnesses usually is of such a degree that either intubation or tracheostomy is necessary.

Several instances of laryngotracheobronchopneumonitis with toxic shock syndrome have been observed.21,31,166,202,209 Generally, children with these staphylococcal infections initially have the onset of croup, then the more severe manifestations of bacterial tracheitis develop, and finally the exanthem and other manifestations of toxic shock syndrome develop. An infant with tracheitis and supraglottitis caused by M. catarrhalis has been described.2 Other findings in laryngotracheobronchitis and laryngotracheobronchopneumonitis are presented in Table 22-4.

Laryngotracheobronchitis

Laryngotracheobronchitis (croup) is a common childhood infection. It is caused by a variety of infectious agents; parainfluenza virus, coronavirus, and rhinovirus are the most common.33 This is a seasonal illness, occurring predominately during winter months, and most commonly affecting children from age 6 months to 3 years. There is frequently a history of prodromal infection accompanied by an unusual cough (described as sounding like the bark of a seal). Swelling of the tracheal mucosa in the subglottic region causes airway compromise (Figure 44-8). Medical attention is usually sought when the child develops inspiratory stridor and respiratory distress. Various scales have been devised to quantify the severity of the stridor to document the progression of the illness and the response to therapy. One of the most commonly employed scales is the Westley scale,34 which has been validated (see Table 44-1).35

When a chest radiograph is obtained during an episode of laryngotracheobronchitis, the trachea is seen to have a gradual progressive narrowing of its lumen, reaching the narrowest point just below the vocal cords (the “steeple sign”) (Figure 44-9). The upper glottis, as seen on a lateral neck radiograph, is normal.

Many care providers believe that exposing the child to cold or misty air often dramatically improves the symptoms; although evidence in support of this therapy is lacking.36,37 When the illness is refractory to these measures, racemic epinephrine has been shown to produce dramatic reduction of airway obstruction. This probably is accomplished by stimulation of the α-adrenergic receptors, producing vasoconstriction and resulting in diminished tracheal edema. Rebound tracheal edema may occur several hours later as the effect of the racemic epinephrine dissipates. Because this problem is unpredictable, the child should be admitted to the hospital for observation after racemic epinephrine has been used.

The practice of treating laryngotracheobronchitis with corticosteroids is widespread, especially for hospitalized patients.38 Oral, intramuscular, and nebulized corticosteroids have been shown to be beneficial in randomized, blinded trials.39,40 Meta-analyses in which the efficacy of corticosteroids was evaluated suggest that corticosteroids reduced the need for endotracheal intubation or inhaled epinephrine, hasten improvement in the first 24 hours of illness, shorten the duration of hospitalization, and reduce the frequency of readmission.41-44

Mixtures of 70% helium and 30% oxygen (heliox) may be beneficial because the characteristics of this mixture permit greater gas flow past areas of airway narrowing. Some authors suggest that this therapy is as efficacious as racemic epinephrine45; however, this therapy has not been conclusively demonstrated to be superior to the administration of supplemental oxygen by itself.46

Endotracheal intubation is occasionally necessary when laryngotracheobronchitis proves refractory to medical intervention. Unless merited by special circumstances, such as severe subglottic stenosis in association with laryngotracheobronchitis, tracheostomy offers no advantages over endotracheal intubation. The endotracheal tube should be of a smaller size than would normally be used, to avoid additional injury to the swollen tracheal mucosa. If the tracheal edema is severe, even a small tube may fit tightly in the trachea.

Later, when an audible leak around the endotracheal tube is present, the trachea may be extubated with a high probability that reintubation will not be necessary.47 If a leak does not become audible after 2 to 4 days, it is our practice to extubate the trachea, because prolonged intubation may increase the risk for subglottic injury. Racemic epinephrine is commonly needed to treat stridor after extubation. If a patient should have especially severe or recurrent laryngotracheobronchitis, an anatomic lesion causing tracheal narrowing should be suspected.

Laryngotracheobronchitis

Laryngotracheobronchitis (croup) is a common childhood infection. It is caused by a variety of infectious agents; parainfluenza virus A, adenovirus, and respiratory syncytial virus are the most common. This is a seasonal illness, happening mainly during the winter, and it most commonly affects children from age 6 months to 3 years. There is frequently a history of prodromal infection accompanied by an unusual cough (described as sounding like the bark of a seal). Swelling of the tracheal mucosa in the subglottic region causes airway compromise (Fig. 39-8). Medical attention is usually sought when the child develops inspiratory stridor and respiratory distress. Various scales have been devised to quantify the severity of the stridor to document the progression of the illness and the response to therapy (Table 39-1). Radiographically, the trachea is seen to have a gradual progressive narrowing of its lumen, reaching the narrowest point just below the vocal cords (the “steeple sign”) (Fig. 39-9). The upper glottis as seen on a lateral neck radiograph is normal.

Exposing the child to cold or misty air often dramatically improves the symptoms. When the illness is refractory to these measures, racemic epinephrine has been shown to produce dramatic reduction of airway obstruction. This probably is accomplished by stimulation of the α-adrenergic receptors producing vasoconstriction and resulting in diminished tracheal edema. Rebound tracheal edema may occur several hours later as the effect of the racemic epinephrine dissipates. Because this problem is unpredictable, the child should be admitted to the hospital for observation after racemic epinephrine has been used.

The practice of treating laryngotracheobronchitis with corticosteroids is widespread, especially for hospitalized patients.22 Oral, intramuscular, and nebulized corticosteroids have been shown to be beneficial in randomized, blinded trials.23, 24 Multiple meta-analyses in which the efficacy of corticosteroids were evaluated suggest that corticosteroids reduced the need for endotracheal intubation or inhaled epinephrine, hasten improvement in the first 24 hours of illness, shorten the duration of hospitalization, and reduce the frequency of readmission.25–27

Mixtures of helium and oxygen (heliox) have proven beneficial in settings with airway narrowing and turbulent air flow.28 Because this gas mixture is less dense than air, turbulent flow past the airway obstruction is facilitated, resulting in lower airway resistance and improved gas exchange. The efficacy of this therapy depends on the quantity of helium present in the gas mixture. Gas mixtures containing less than 60% helium show little benefit compared with air. This limits the application of this therapy to patients who can tolerate a fractional concentration of oxygen in inspired gas (Fio2) of 40% or less. To avoid the risk of hypoxemia, mixtures of 79% helium and 21% oxygen are commercially available. If supplemental oxygen is required, additional oxygen can be added to this mixture; care must be taken not to exceed an Fio2 of 40%. Because the density of this gas mixture is different than air or oxygen, specially calibrated flow meters are necessary. No adjustment is necessary if an oxygen electrode is used to measure the Fio2. This mixture must be delivered through a facemask. Delivery through a nasal cannula or an infant Oxyhood is ineffective.29 In the latter case, a concentration gradient of helium and oxygen is rapidly established, with the greatest concentration of helium at the top of the hood. A recent randomized study has shown that heliox will result in similar improvements in severe croup as compared with racemic epinephrine.30

Endotracheal intubation is occasionally necessary when laryngotracheobronchitis proves refractory to medical intervention. The use of tracheostomy to treat life-threatening laryngotracheobronchitis is much less common now than formerly. Unless merited by special circumstances, such as severe subglottic stenosis in association with laryngotracheobronchitis, tracheostomy offers no advantages over endotracheal intubation. For placement of the endotracheal tube to be facilitated and for injury to the tracheal mucosa to be reduced, the endotracheal tube should be of a smaller size than would normally be used. If the tracheal edema is severe, even a small tube may fit tightly in the trachea.

Later, when an audible leak around the endotracheal tube is present, the trachea may be extubated with a high probability that reintubation will not be necessary.31 If a leak does not become audible after 2 to 4 days, it is our practice to extubate the trachea because prolonged intubation may increase the risk for subglottic injury. Racemic epinephrine is commonly needed to treat stridor after extubation. If a patient should have especially severe or recurrent laryngotracheobronchitis, an anatomic lesion causing tracheal narrowing should be suspected.

Laryngotracheobronchitis (Croup)

Laryngotracheobronchitis (LTB), or croup, is a viral upper respiratory tract infection most commonly caused by parainfluenza virus types I, II, and III1 and influenza virus types A and B. Croup typically affects children between 6 months and 3 years of age, with a peak incidence at 2 years of age.2 It is the most common cause of upper airway obstruction in patients between 6 months and 6 years of age.3

Children with croup typically present with a 2- to 6-day history of an antecedent upper respiratory tract infection that progresses to the characteristic barking cough, biphasic stridor, and hoarseness. Fever and leukocytosis may also be present. The pathophysiology of croup involves symmetrical narrowing of the subglottis secondary to mucosal edema.

The diagnosis of croup is mainly based on history and physical examination. Anteroposterior neck radiographs demonstrating symmetrical subglottic narrowing, the steeple sign (Fig. 11-1), will support the diagnosis; however, radiographic findings are neither sensitive nor specific. Endoscopic evaluation of the larynx, which is usually not indicated, reveals edematous, erythematous, subglottic tissues below the true vocal folds, without significant secretions (Fig. 11-2).

Treatment includes the use of humidified air, nebulized racemic epinephrine, and steroids. The use of humidified air is based on mainly anecdotal evidence and is believed to soothe inflamed mucosa and improve clearance of secretions.2 Nebulized racemic epinephrine provides a temporary reduction in airway resistance, presumably through α-adrenergic–mediated vasoconstriction within the edematous subglottic mucosa and β-adrenergic–mediated bronchodilation.3

Corticosteroids are often used in both the outpatient and inpatient treatment of moderate to severe croup. Although their exact mechanism of action is unknown, corticosteroids may potentially decrease vascular permeability and thus mucosal edema.4,5 Most clinicians will give severely affected children a single dose of steroids at 0.6 to 1.5 mg/kg dexamethasone equivalent.2,3

Intubation and tracheostomy should be avoided, if possible, but are occasionally necessary to secure the child's airway. If intubation is required, an endotracheal tube at least one-half to one size smaller than normal is recommended to minimize the risk of acquired subglottic stenosis.

An endoscopic airway evaluation should be considered in patients with recurrent croup who are younger than 1 year of age, patients with persistent airway symptoms between episodes of croup, patients with severe, atypical, or recurrent croup,2,3 and patients who respond poorly to therapy. Ideally, endoscopy is performed 3 to 4 weeks after an episode of croup to allow time for resolution of the acute inflammation.

Inflammatory Disease of the Upper Airway

Laryngotracheobronchitis (viral croup) is an inflammation of the subglottic airway caused by a variety of parainfluenza and influenza viral agents. The infection may involve the entire glottis and extend into the trachea and bronchi. Affected children fall typically into the 1- to 3-year age group; males are more commonly affected than females. Symptoms and signs of viral croup include biphasic stridor, barking cough, and hoarseness, often in association with a prodromal viral upper respiratory tract infection. The diagnosis of croup is made clinically, but endoscopic examination may help to exclude other pathologic processes. Care should be taken not to instrument the subglottis, causing more swelling and inflammation and precipitating acute obstruction. Lateral neck radiography demonstrates subglottic narrowing, whereas anteroposterior neck films show a “steeple sign,” the result of subglottic edema. Treatment of viral croup is typically supportive with humidification. Use of corticosteroids remains controversial. Treatment with nebulized racemic epinephrine in the emergency department or hospital setting often relieves symptoms; however, rebound of signs may occur several hours later and children should be monitored accordingly. Severely affected children may require intubation for respiratory failure. A smaller than normal tube should be employed. In rare cases, a tracheostomy may be required if the inflammation fails to resolve.

A child younger than 1 year of age with recurrent bouts of “croup” should be suspected of having either congenital subglottic stenosis or a hemangioma. Spasmodic croup is the recurrence of croup-like symptoms in a child who is otherwise well. Fever is rarely present, and the attacks frequently occur at night. Gastroesophageal reflux disease has been suggested as a possible inciting process. Treatment of spasmodic croup is usually observant, although corticosteroids or reflux medications may prove beneficial.

Supraglottitis (epiglottitis) is an infectious disease that involves the supraglottic larynx. In children the typical pathogen is type B Haemophilus influenzae (HIB). Other pathogens have been implicated in adolescent and adult cases. The incidence of supraglottitis in children has diminished markedly since the introduction of the conjugated HIB vaccine in the early 1990s.17 Affected children are somewhat older than those seen with croup—in the 3- to 6-year age group. Symptoms and signs have a rapid onset, progress quickly to frank airway obstruction, and include stridor, dysphagia, fever, muffled voice, and signs of systemic toxicity. Affected children frequently sit and assume the “sniffing” position in an attempt to maximize their airway. Intraoral or endoscopic examination should be avoided in suspected patients because of concern for precipitating complete obstruction. Lateral neck radiography demonstrates a classic “thumbprinting” of the epiglottis but should only be obtained if facilities are present in close proximity to secure the airway.

Prompt airway management is essential in children with supraglottitis. The child's airway should be secured in either the emergency department or operating room with team members who include a pediatrician, anesthesiologist, critical care physician, otolaryngologist, or pediatric surgeon or others familiar with the pediatric airway. After inducing the child with general anesthesia, the airway should be intubated. Examination of the supraglottis may be made, and cultures of the larynx and blood are obtained. Equipment to perform a tracheostomy should be readily available. The child should remain intubated for 24 to 72 hours and should be supported with intravenous fluids and antibiotics that treat antibiotic-resistant Haemophilus (third-generation cephalosporins, chloramphenicol).

Bacterial tracheitis (membranous croup) often occurs as a complication of another infection, such as measles, varicella, or other viral agents. The most common organisms include S. aureus, GABHS, M. catarrhalis, or H. influenzae. It can occur in any age child and present with stridor, barking cough, and low-grade fever. Symptoms and signs then progress to include high fever and increasing obstruction and toxicity. The diagnosis may be suspected by diffuse narrowing of the tracheal air shadow on chest radiograph but is confirmed by endoscopic examination in the operating room. Purulent debris and crusts can be removed at this time. Cultures of secretions and crusts may be helpful in guiding intravenous antibiotic therapy that should be aimed initially at the usual pathogens. The airway should be secured with an endotracheal tube or, rarely, a tracheostomy. Repeat endoscopic examination of the airway may be warranted to continue débridement and to determine the feasibility of extubation.

Inflammatory disease of the upper airway

Laryngotracheobronchitis (viral croup) is an inflammation of the subglottic airway caused by a variety of parainfluenza and influenza viral agents. The infection may involve the entire glottis and extend into the trachea and bronchi. Affected children fall typically into the 1- to 3-year-old group; males are more commonly affected than females. Symptoms and signs of viral croup include biphasic stridor, barking cough, and hoarseness, often in association with a prodromal viral upper respiratory tract infection. The diagnosis of croup is made clinically, but endoscopic examination may help to exclude other pathologic processes. Care should be taken not to instrument the subglottis, causing more swelling and inflammation and precipitating acute obstruction. Lateral neck radiography demonstrates subglottic narrowing, whereas anteroposterior neck films show a “steeple sign,” the result of subglottic edema. Treatment of viral croup is typically supportive with humidification. Treatment with nebulized racemic epinephrine in the emergency department or hospital setting often relieves symptoms; however, rebound of signs may occur several hours later, and children should be monitored accordingly. A meta-analysis of randomized controlled trials has shown treatment with glucocorticoids is effective in improving symptoms within 6 hours, for up to 12 hours, with significant improvement in croup scores, shorter hospital stays, and less use of epinephrine.35 Severely affected children may require intubation for respiratory failure (less than 5% of affected patients). A smaller than normal tube should be chosen to avoid edema and scarring. In rare cases, a tracheostomy may be required if the inflammation fails to resolve.

A child younger than 1 year of age with recurrent bouts of “croup” should be suspected of having either congenital subglottic stenosis or a hemangioma. Spasmodic croup is the recurrence of crouplike symptoms in a child who is otherwise well. Fever is rarely present, and the attacks frequently occur at night. Gastroesophageal reflux disease has been suggested as a possible inciting process. Treatment of spasmodic croup is usually observant, although corticosteroids or antireflux medications may prove beneficial.

Supraglottitis (epiglottitis) is an infectious disease that involves the supraglottic larynx. In children, the most common pathogen is Haemophilus influenzae type B (HIB), followed by S. pneumoniae and S. aureus. The incidence of supraglottitis in children has diminished markedly since the introduction of the conjugated HIB vaccine in the early 1990s.36 However, HIB-related supraglottitis continues to occur in children who have been vaccinated, with a reported 2% vaccine failure rate. Alternatively, S. pneumoniae, S. aureus, and viruses are more likely to cause supraglottitis in adolescents and adults.

Children who develop supraglottitis are somewhat older than those seen with croup in the 2- to 6-year-old group. Symptoms and signs have a rapid onset, progress quickly to frank airway obstruction, and include stridor, dysphagia, fever, muffled voice, and signs of systemic toxicity. Affected children frequently sit and assume the “sniffing” position in an attempt to maximize their airway. Intraoral or endoscopic examination should be avoided in suspected patients because of concern for precipitating complete obstruction. Lateral neck radiography demonstrates a classic “thumbprint sign” of the epiglottis but should only be obtained if facilities are present in close proximity to secure the airway.

Prompt airway management is essential in children with supraglottitis. In severe cases, the child's airway should be secured in either the emergency department or operating room with team members, including a pediatrician, anesthesiologist, critical care physician, otolaryngologist, or pediatric surgeon or others familiar with the pediatric airway. After inducing the child with general anesthesia, the airway should be intubated. Examination of the supraglottis may be made, and cultures of the larynx and blood are obtained. Equipment to perform a tracheostomy should be readily available. The child should remain intubated for 24 to 72 hours and should be supported with intravenous fluids and antibiotics that treat antibiotic-resistant H. influenzae, S. pneumoniae, and S. aureus (third-generation cephalosporins or ampicillin-sulbactam).

Bacterial tracheitis (membranous croup) often occurs as a complication of another infection, such as measles, varicella, or other viral agents. The most common organisms include S. aureus, GABHS, M. catarrhalis, or H. influenzae. It can occur in any age child and present with stridor, barking cough, and low-grade fever. Symptoms and signs then progress to include high fever and increasing obstruction and toxicity. The diagnosis may be suspected by diffuse narrowing of the tracheal air shadow on chest radiograph but is confirmed by endoscopic examination in the operating room. Purulent debris and crusts can be removed at this time. Cultures of secretions and crusts may be helpful in guiding intravenous antibiotic therapy that should be aimed initially at the usual pathogens. The airway should be secured with an endotracheal tube or, rarely, a tracheostomy. Repeat endoscopic examination of the airway may be warranted to continue debridement and to determine the feasibility of extubation.

Croup (Laryngotracheobronchitis)

Laryngotracheobronchitis, also commonly known as croup, is typically a viral disease of the larynx and trachea. It is the most common infectious cause of stridor in children. An estimated 3% to 5% of children have at least one episode of croup during childhood. Children are most commonly affected when they are between 6 months and 3 years of age. There is a strong seasonal occurrence in late autumn and winter, but it can occur any time of year.

Parainfluenza viruses (types 1, 2, and 3) are implicated in the vast majority of children with croup (approximately 80%)63; however, a host of other viruses can cause croup symptoms, including influenza A and B, RSV, and adenovirus.64–67 Rarely measles, varicella, HSVs, and Mycoplasma pneumoniae are etiologies.68,69 Viral croup transmission may occur by direct contact and exposure to nasopharyngeal secretions or through airborne droplets over short distances.70 The incubation period is 2 to 6 days for parainfluenza virus type 1, and children may continue to shed the virus for up to 2 weeks.71 The viral infection initially involves the nasopharynx, followed by spread to the larynx and trachea, particularly the vocal folds and subglottis.

Characteristically, croup infections are preceded by 1 to 2 days of a nonspecific viral prodromal URI with low-grade fever. Classically, this evolves into a triad of hoarseness, stridor with a distinct expiratory component (seal-like barking cough), and varying degrees of upper airway obstruction. Children do not usually appear toxic. The mean duration of illness is usually 2 to 3 days, with resolution of symptoms within 2 days in 80% of children.72

Croup most often presents with only mild symptoms, but it can also cause severe, life-threatening airway obstruction. Box 22.1 lists important physical examination findings for the evaluation of the child with croup.

The presence of biphasic stridor, retractions, high respiratory rate, oxygen desaturations, or altered consciousness indicates severe airway obstruction. Some 6% to 10% of children with croup require hospital admission for upper airway obstruction,73 and 3% to 10% require critical care services.74 As the subglottis is both the narrowest portion of the airway in children and is the only complete cartilaginous ring, it is particularly susceptible to obstruction by edema. Because stridor does not occur until airway obstruction is already significant, any further decrease in airway size caused by mucus plugging or crusting may lead to rapid and complete airway obstruction.

History and physical examination alone are sufficient for the diagnosis of croup. Radiographic evaluation with high-kilovoltage anteroposterior and lateral films of the upper airway is a useful adjunct (Figs. 22.4A and 22.5). In croup, the anteroposterior view classically shows a “steeple sign” in the subglottic area (see Fig. 22.4B). The classic radiographic findings may be absent in 50% of patients and are also not pathognomonic for croup.75

Flexible fiberoptic laryngoscopy (Fig. 22.6A) may occasionally be helpful in establishing the correct diagnosis of viral croup, but it must be performed with extreme caution to avoid inducing acute airway obstruction in children with moderate to severe obstructive symptoms. In patients with severe airway obstruction, an uncertain diagnosis, or risk factors for other airway pathology, direct laryngoscopy and bronchoscopy are warranted.63 Classic endoscopic findings of croup include edema and narrowing of the vocal folds and subglottis (see Fig. 22.6B). However, endoscopy cannot completely assess for anatomic abnormalities when it is performed during acute infectious illness.

In the acute setting, the most important alternative diagnoses to consider are other life-threatening airway infections, particularly epiglottitis (Table 22.6). A careful history is essential for consideration of an airway foreign body, bacterial tracheitis, retropharyngeal abscess, thermal injury, or caustic ingestion. Croup should be considered atypical if it occurs in infants younger than 6 months of age, lasts more than 7 days, is unusually severe, or does not respond to appropriate treatment; a wider differential should be considered in these atypical cases. Croup can be recurrent in approximately 5% of children,76,77 and studies have suggested that congenital subglottic narrowing and gastroesophageal reflux disease are the most common etiologies of recurrent croup.78,79 Asthma and allergy have also been implicated.80 In a study of children affected by croup who required hospitalization, over half with recurrent episodes of croup within a 9-year follow-up period were diagnosed with allergies.80 Other studies have shown that a history of croup doubles the odds of asthma and wheezing in children.81,82 Spasmodic croup, which involves nighttime acute episodes of crouplike symptoms without a preceding viral prodrome, is also linked to allergic reactivity and gastroesophageal reflux disease. Other causes may be acquired subglottic stenosis, subglottic hemangioma (especially in infants), or other anatomic abnormalities. Further evaluation of children with recurrent or persistent croup may be warranted. Flexible laryngoscopy or a pH probe study may help identify reflux disease. Some advocate for complete endoscopic airway evaluation in all cases78; however, endoscopy will not alter treatment in the vast majority.83 Risk factors for more severe disease requiring endoscopic evaluation include a history of intubation, age less than 1 year, and episodes that require hospital admission.83

Viral croup is typically self-limited and does not require medical evaluation or intervention. Home measures include parental reassurance and keeping the child calm by limiting stimuli that promote crying and agitation. Patients who present for medical evaluation can be managed with several modalities that include systemic glucocorticoids, racemic epinephrine, and an inspired mixture of helium and oxygen (heliox). Clinical croup algorithms promote consistent, safe, and effective management.84

Corticosteroids have a marked effect on the severity and length of symptoms and can lead to a significant drop in return visits, hospital admissions, length of stay, intubations, and use of epinephrine.74,85–87 Both oral and intravenous forms of administration appear equally efficacious.88,89 Studies comparing low- to high-dose corticosteroids have been equivocal,90–93 and a maximum dose has not been established.86 Low-dose oral administration (1 to 2 mg/kg/day divided twice daily) is the preferred delivery for ambulatory settings. Intravenous administration of doses that range from 0.15 to 0.6 mg/kg is preferable for severe disease in inpatient settings.86,94

Aerosolized racemic epinephrine (l- and d-epinephrine) or l-epinephrine alone are adrenergic agents that rapidly improve symptoms of airway obstruction by reducing airway edema via vasoconstriction and decreased vascular permeability. The effect is more rapid than glucocorticoids, but these agents are considered second-line therapy after steroids because of side effects (tachycardia, agitation, hypertension) and short duration of action. In addition, because of the risk of rebound, children in outpatient settings should be observed closely for 3 to 4 hours after administration before being discharged. In the inpatient setting, adrenergic agents can be used as frequently as every 30 minutes but are typically administered every 3 to 4 hours. Use in combination with glucocorticoids may reduce rebound and provide improved efficacy.95,96 Aerosolized epinephrine should be used with great caution in patients with tachycardia or cardiac anomalies such as tetralogy of Fallot or idiopathic subaortic stenosis. l-epinephrine is readily available worldwide and is less expensive and at least as effective as racemic epinephrine.97,98

Heliox, a helium-oxygen mixture, has been used in croup and is thought to reduce airway obstruction by promoting gas flow through the partially obstructed airway, although a 2013 meta-analysis points to insufficient data to support its use.99

Humidified air has long been used to treat croup based on the presumption that it moistens secretions, facilitates comfort and expectoration, and prevents drying or crusting, which could further compromise a narrow airway. However, meta-analyses concur that significant benefit has yet to be proved.86,94,100,101

Admission should be considered if initial therapy is ineffective, in those children with severe symptoms (decreased level of consciousness, worsening work of breathing, infants younger than 6 months), or when social circumstances raise concerns about follow-up and appropriate access to care.63,86 In patients with persistent severe airway compromise, endotracheal intubation may be necessary. Intubation should be done in a controlled situation in the operating room (OR) with the child breathing spontaneously. Endoscopic examination should be done with caution to avoid airway mucosal injury or further compromise; the size of the endotracheal tube should be at least a half size smaller than that estimated for the child’s size. Extubation can be performed when an air leak is detected. If no air leak is detected after 5 to 7 days, thorough airway endoscopy is indicated.

b Laryngotracheobronchitis or Croup

In laryngotracheobronchitis or croup, the subglottic larynx is involved. This condition affects younger children and has a less fulminant course than acute epiglottitis. The swelling of the soft tissues in the subglottic neck can be appreciated on an AP view of the neck (Fig. 2-19). There is usually a long segment narrowing of the glottis and subglottic airway with loss of the normal angle between the vocal cords and the subglottic airway. This has been referred to as the “steeple sign.” The hypopharynx is usually dilated because of the airway obstruction distally.

Epidemiology

Viral LTB is the most common cause of infective upper airway obstruction in the pediatric age group. Affected children are usually of preschool age, with a peak incidence between 18 and 24 months of age.7 Although viral LTB episodes become uncommon beyond 6 years of age, cases have been reported during later childhood and adolescence, and rarely described in adults. Reported annual incidence rates in preschool children vary from 1.5% to 6%, but less than 5% of these require hospital admission, and only 1% to 2% of those admitted require endotracheal intubation and intensive care.8 This proportion has fallen dramatically since the use of corticosteroids has become routine. Mortality is low, reported by one 10-year follow-up study as less than 0.5% of intubated patients.9 There is a male preponderance in children younger than 6 years of age (1.4 : 1), although both sexes appear to be affected equally at an older age.

Children with a specific CD14 genetic polymorphism (C/C variant of CD14 C-159T) have recently been described as having a reduced prevalence of croup. It has been hypothesized that this relates to the role of the CD14 gene as a pattern recognition receptor in the mediation of the innate immune system response to LTB-causing viruses.10

Cases may occur in epidemics, with those caused by parainfluenza virus (PIV) type 1 typically presenting in fall and winter months. Infections caused by other common organisms, including other PIV subtypes, occur more commonly as isolated infections. Infection is via droplet spread or direct inoculation from the hands. Viruses can survive for long periods on dry surfaces, such as clothes and toys, emphasizing the importance of infection-control practices.