CHAPTER 168 

Pediatric Respiratory Emergencies: Upper Airway Obstruction and Infections Jeffrey Cukor and Mariann Manno

PERSPECTIVE Respiratory distress from upper airway obstruction is an unusual but potentially catastrophic emergency in young children. It may be caused by a number of different processes, including an acute infectious process, a congenital anomaly, and a foreign body in the airway or esophagus. A working knowledge of the diseases of the upper airway is of critical importance in pediatric emergency medicine. Classification of airway disease can be based on the anatomic location, the patient’s age, and whether it is congenital or acquired. Treatment is based on the underlying pathologic process and the urgency of the symptoms. The starting point for any classification is an appreciation of the unique aspects of pediatric airway anatomy.

DISTINGUISHING PRINCIPLES OF DISEASE A number of differences between the adult and pediatric airway are important in airway management (Fig. 168-1). An infant’s tongue is disproportionately large in relation to the mouth and protrudes back into the posterior of the pharynx. In the setting of hypotonia, posterior displacement of the tongue is the most common cause of functional upper airway obstruction. The infant larynx is more anterior and higher in the neck relative to the cervical spine (at C3-4) compared with an adult larynx (C4-5). The anterior aspect of the vocal cords is tipped inferiorly. The narrowest site of the infant airway is at the cricoid ring rather than the cords as in an adult. A child’s epiglottis is relatively larger, longer, and omega shaped. It extends vertically beyond the opening of the cords, thus making a complete view of the airway difficult. The caliber of all airway structures is small; on average, newborn tracheal length is 57 mm and laryngeal diameter is 4 mm. All cartilaginous supporting structures are soft, pliable, and prone to collapse. Finally, a prominent occiput causes passive flexion of the head and neck on the cervical spine. In aggregate, these anatomic features of the pediatric airway predispose infants and young children to functional upper airway obstruction and make airway intervention technically challenging. The type and size of equipment required for management of the pediatric airway are derived from this unique anatomy. A face mask should be sized so that the top and bottom rims fit on the bridge of the nose (below the eye) and in the cleft of the chin. A straight (Miller) blade is generally used for endotracheal intubation in infants and young children because the tip of the straight blade lifts the epiglottis up and out of the line of vision of the airway. Endotracheal tube size is a function of the patient’s size. For children older than 1 year, endotracheal tube size (internal diameter in millimeters) can be estimated by the formula (age in 2106

years/4) + 4; for uncuffed tubes, a half size smaller than calculated should be used, except for 3.0-mm tubes. Alternatively, endotracheal tube size can also be estimated by use of a length-based measuring system, such as the Broselow-Luten tape. Recent evidence suggests that cuffed endotracheal tubes may be used safely in children of all ages. Cuffed endotracheal tubes allow the delivery of high pressures during ventilation without the air leak associated with uncuffed tubes and without increased complications, such as subglottic stenosis.1 There is a broad spectrum of clinical presentations in children with upper airway disease. It is important to consider the following general concepts: • Acute infections of the upper airway range from relatively mild distress and self-limited signs and symptoms to the abrupt onset of a rapidly progressive airway obstruction. • Undiagnosed congenital anomalies of the airway and surrounding structures may be manifested as chronic or progressive stridor or simply difficulty in feeding. An infant with a congenital airway anomaly in whom an acute airway infection develops is at higher risk for decompensation and respiratory failure. • Upper airway obstruction from a foreign body in the airway or esophagus can cause partial or complete airway obstruction and may require urgent advanced airway management skills.

STRIDOR Stridor is the classic sound associated with upper airway obstruction.2-4 It is derived from the Latin stridulus, meaning harsh or grating. Stridor is caused by partial airway obstruction and the resultant turbulent airflow through some portion of the airway from the nose to the trachea. It is not a diagnosis in itself but an important sign that must be investigated in the symptomatic patient. Stridor should be described in its timing within the respiratory cycle (inspiratory, expiratory, biphasic) and by its quality (coarse or high pitched) (Table 168-1). The upper airway can be artificially divided into four regions: the nose and pharynx, the supraglottic structures, the glottis and immediate subglottic area, and the intrathoracic trachea (Fig. 168-2). The characteristics of stridor differ by its cause and its precise origin in the airway. Stridor from the nose or pharynx, such as from a peritonsillar abscess, tends to have a sonorous, gurgling, and coarse quality. The voice may be altered and have a muffled or “hot potato” quality to it. In contrast, conditions involving the supraglottic and immediate subglottic trachea, as with croup and laryngomalacia, usually have a higher pitched inspiratory stridor sound. The stridor is created by the forced narrowing of the extrathoracic airway

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Prominent occiput

Tongue is disproportionately large in relation to mouth

C3

Larynx is higher in neck

C4

Narrowest portion at cricoid ring

Tongue C3 C4 C5

Larynx

Figure 168-1.  Comparison of adult and pediatric airways. (From Finucane BT: Principles of Airway Management. Philadelphia, FA Davis, 1988.)

Table 168-1 Causes of Stridor: Anatomic Location, Sound, and Etiology FEATURES

SUPRAGLOTTIC

GLOTTIC

SUBGLOTTIC TRACHEA

Sound

Sonorous Gurgling Coarse Expiratory stridor

Biphasic stridor

High-pitched stridor Inspiratory stridor

Structures

Nose Pharynx Epiglottis

Larynx Vocal cords

Subglottic trachea

Congenital

Micrognathia Pierre Robin syndrome Treacher Collins syndrome Macroglossia Down syndrome Storage diseases Choanal atresia Lingual thyroid Thyroglossal cyst

Laryngomalacia Vocal cord paralysis Laryngeal web Laryngocele

Subglottic stenosis Tracheomalacia Tracheal stenosis Vascular ring Hemangioma cyst

Acquired

Adenopathy Tonsillar hypertrophy Foreign body Pharyngeal abscess Epiglottitis

Papillomas Foreign body

Croup Bacterial tracheitis Subglottic stenosis Foreign body

structures as the atmospheric pressure inside the airway becomes slightly lower than outside the airway. In these cases the voice may sound hoarse or weak. Biphasic stridor is heard with inspiration and expiration and usually suggests a fixed lesion that does not change with respiration. Examples of conditions resulting in biphasic stridor are laryngeal webs and vocal cord paralysis. Stridor from the lower part of the trachea is usually expiratory. Bacterial tracheitis and foreign bodies are examples.

OVERVIEW OF THE EVALUATION AND MANAGEMENT OF A CHILD WITH AN UPPER AIRWAY OBSTRUCTION Evaluation of a child with signs of airway obstruction begins with careful observation of the child both at rest and during activity (crying, feeding), noting the work of breathing, respiratory rate, alertness, and color. In most cases, observation and a

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Supraglottic • Craniofacial Pierre Robin Treacher Collins Hallermann-Streiff • Macroglossia Beckwith-Wiedemann Down syndrome Glycogen storage disease Congenital hypothyroidism • Choanal atresia • Encephalocele • Thyroglossal duct cyst • Lingual thyroid

Laryngeal • Laryngomalacia • Vocal cord paralysis • Congenital subglottic stenosis • Laryngeal web • Laryngeal cyst • Subglottic hemangioma • Laryngotracheoesophageal cleft Intrathoracic • Tracheomalacia • Tracheal stenosis • Vascular rings/slings • Mediastinal masses

Figure 168-2.  Regions and associated diseases of the pediatric upper airway. (From Simon NP, Simon N: Evaluation and management of stridor in the newborn. Clin Pediatr [Phila] 30:211, 1991.)

carefully obtained history will provide clues to the correct diagnosis. Important items to elucidate in the history include the following: • Onset and duration (acute vs. chronic) • Associated symptoms (respiratory distress, fever, toxicity, drooling, cyanosis) • Progression with age (number of bouts and severity of “croup” with increasing age) • Exacerbating factors (supine vs. prone position, upper respiratory infection [URI], crying) • Feeding pattern (dysphagia, feeding abnormalities) • Prior airway procedures (intubation in the neonatal period) • Choking episode (foreign body aspiration) • Baseline noises, quality of cry and voice (to help in location of obstructive lesion) The initial physical examination should assess vital signs (respiratory rate, heart rate, oxygen saturation) and mechanics of breathing (retractions, flaring, grunting) to determine the severity of distress. Respiratory failure is identified by the presence of extreme distress, hypoventilation or hyperventilation, altered mental status, dusky skin color, cyanosis, or hypotonia. The character and timing of stridor, if it is present, as well as the symmetry and quality of breath sounds are also important observations. Definitive airway management always takes precedence over laboratory and radiographic tests in a patient with an acute airway emergency. In a stable patient with an uncertain diagnosis, an individualized diagnostic evaluation is undertaken. Radiographs of the soft tissues of the neck may be helpful and should include both lateral and anteroposterior views. These views assess the adenoid and tonsillar size, the contour of the epiglottis, the thickness of the retropharyngeal soft tissue space, the vallecula, the aryepiglottic folds, and the tracheal air column (Fig. 168-3).5,6 Optimally, the child’s head should be positioned in extension and the film taken during inspiration. Views of the chest may be helpful to assess the heart size, the trachea and bronchi,

Retropharyngeal space Epiglottis Hyoid bone Tracheal air column

Figure 168-3.  Normal appearance of upper airway structures on a lateral neck radiographic study. Note the hyoid bone, epiglottis, retropharyngeal space, and tracheal air column.

the location of the aortic arch, and the presence of other pulmonary pathologic processes. Additional studies may be indicated in specific settings. Bedside fiberoptic nasopharyngoscopy can be performed without general anesthesia and allows visualization and assessment of the supraglottic structures and the vocal cords. The nasopharyngoscope may also be used to aid with a fiberoptic-assisted intubation. Esophagography can help define lesions compressing the airway and trachea; computed tomography (CT), magnetic resonance imaging (MRI), and bronchoscopy also may have roles in evaluating the upper airway and should be considered on an individual basis.

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SPECIFIC DISORDERS Supraglottic Airway Diseases Perspective The supraglottic portion of the airway includes the nose, pharynx, epiglottis, and surrounding structures. Disease of the nose and pharynx is commonly associated with noisy, congested breathing and respiratory distress. Congenital lesions involving these structures may cause mild symptoms at baseline but dramatic distress when there is a superimposed infectious process. Congenital lesions with which the emergency physician should be familiar include choanal atresia, macroglossia, micrognathia, thyroglossal duct cyst, and lingular thyroid. Important acquired causes of supraglottic disease include nasal foreign body, nasal polyps, hypertrophic tonsils and adenoids, epiglottitis, retropharyngeal abscess, peritonsillar abscess, pharyngitis, mononucleosis, and upper airway foreign body. The most common ones are discussed in the following sections.

Congenital Lesions Choanal atresia, the most common congenital anomaly of the nose, is caused by persistence of the bucconasal membrane or a bony septum in the posterior naris. Infants are “obligate nose breathers” because they breathe nasally when the mouth is closed at rest and to maintain breathing while feeding. In infants, the posterior aspect of the soft palate extends downward and contacts the tip of the epiglottis. Bilateral choanal atresia is a life-threatening emergency that is identified shortly after birth. Infants with bilateral choanal atresia become acutely distressed and cyanotic at birth and are managed with an oral airway that opens the mouth to allow a passage for breathing. Surgical correction of the obstructing membrane is required. Unilateral choanal atresia may go undetected in the nursery and become apparent only when the normal, patent naris is obstructed by swelling or secretions, most frequently from URI. Macroglossia, an abnormally large tongue that protrudes posteriorly into the hypopharynx, is associated with a number of conditions, including Down syndrome, glycogen storage disease, and congenital hypothyroidism. The increased secretions and swelling often associated with a URI exacerbate the underlying obstruction, and stridor or labored breath sounds are heard. With micrognathia, an abnormally small mandible posteriorly displaces the normal-sized tongue. This is associated with syndromes such as Pierre Robin and Treacher Collins. Signs of obstruction often worsen when the patient is supine.

the most commonly isolated organisms.9 Recent case reports highlight the emerging role of methicillin-resistant Staphylococcus aureus in these infections.10 Clinical Features.  The variable presentation of a retropharyngeal abscess can make it a challenging diagnosis in young children.11-14 Common signs and symptoms include fever, sore throat, neck stiffness or nuchal rigidity, torticollis, trismus, neck swelling, drooling, stridor, and muffled voice. In a prospective study of 17 patients with retropharyngeal abscess, stridor and airway obstruction were observed in approximately half (56%) of the patients.15 This common finding of acute airway obstruction is a function of the high position of the larynx in the neck. Such anatomy places the airway proximate to and easily compressed by the bulging retropharyngeal mass. In patients with airway compression, the clinical appearance can resemble epiglottitis. Reluctance to extend the neck and an unwillingness to look side to side is often seen with retropharyngeal abscess and may help differentiate it from other supraglottic infections.16 With less obvious signs of airway obstruction, patients can exhibit a mixture of symptoms (fever, neck stiffness, generalized toxicity) that may also suggest meningitis or sepsis. Other serious complications of retropharyngeal abscess include aspiration pneumonia, mediastinitis, and empyema. Diagnostic Strategies.  Careful evaluation of airway patency takes precedence in management of a child with a presumed retropharyngeal abscess. Examination of the pharynx may reveal bulging of the posterior pharyngeal wall. A soft tissue lateral view of the neck may be helpful to establish the diagnosis; in the normal patient, the width of the retropharyngeal space should not exceed the diameter of the adjacent vertebral body (Fig. 168-4). In general, soft tissue width should not be larger than 7 mm at C2 or exceed 14 mm at C6. The majority of patients (in some studies 88-100%) will demonstrate retropharyngeal thickening on the lateral neck radiograph.8,17,18 An air-fluid level is more commonly seen with perforations and anaerobic infections. Redundant soft tissue of the retropharyngeal space complicates interpretation of lateral neck films in young infants with a retropharyngeal abscess. Artifactual widening of a normal retropharyngeal space is commonly seen when the radiograph is taken with the head and neck in flexion or during exhalation (or both). CT may be beneficial in delineating the size and extent of an abscess and determining possible impingement on airway structures. Before the patient is

Infectious Etiologies Retropharyngeal Abscess Perspective.  A retropharyngeal abscess is a potentially lifethreatening airway emergency resulting from infection of the retropharyngeal soft tissue space. The retropharyngeal space is a potential space between the posterior pharyngeal wall and the prevertebral fascia that extends from the base of the skull to the level of T2. It is rich in lymph tissue that drains the nose, pharynx, sinuses, and ears. An abscess may result from direct trauma from a fall with an object in the mouth like a toothbrush, suppuration of lymph nodes, contiguous spread of infection, or hematogenous seeding.7 Approximately 50% of pediatric cases occur in children 6 to 12 months of age. Almost all of the pediatric cases occur before 3 years of age, and 96% of all diagnosed pediatric retropharyngeal abscesses are seen before 6 years of age.8 These infections are commonly polymicrobial, with Streptococcus and anaerobes

Figure 168-4.  Retropharyngeal abscess. Note the widened retropharyngeal soft tissue space.

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placed in the CT scanner, the ability to tolerate being supine should be tested, and staff and airway equipment should be immediately available. Management.  The size of the abscess, the degree of airway obstruction, and the overall toxicity of the patient dictate management. The need for intubation or surgical drainage is determined on an individual basis, and these patients generally benefit from involvement of an ear, nose, and throat (ENT) specialist. Intubation can be complicated by distorted anatomy and can lead to abscess rupture.19 Not all retropharyngeal abscesses require surgical drainage as many will respond to intravenous antibiotics. A study by Craig and Schunk showed a resolution rate with antibiotics of 37%.20 Clindamycin is a common appropriate first choice for antibiotic therapy. Peritonsillar Abscess.  Peritonsillar abscess more commonly occurs in older children and teenagers. Although it can cause drooling and a muffled, hot potato voice, severe respiratory distress is less common. Peritonsillar abscess is associated with trismus, bulging or asymmetry of the tonsils, and deviation of the uvula away from the abscess side. Throat pain also may radiate to the ear.7 Treatment involves antibiotics and either incision and drainage or, more commonly, needle aspiration. Posterior pharynx ultrasonography or CT scanning can confirm the diagnosis and help guide treatment. Any drainage effort must take great care to avoid puncture of the proximate carotid artery or aspiration of drained material by the patient. Mononucleosis.  Infectious mononucleosis, caused by the Epstein-Barr virus, can lead to mucosal edema and an exudative pharyngitis. Uncommonly, massive tonsillar enlargement can occur and create upper airway distress. In addition to airway management and general supportive care, some studies have shown benefit of steroids and racemic epinephrine in reducing tonsillar edema.21,22 Ludwig’s Angina.  Ludwig’s angina is a rapidly progressive infection and inflammatory process of the sublingual, submandibular, and submaxillary spaces. Elevation of the tongue above the lower teeth and tenderness in the sublingual space are hallmark signs along with trismus and odynophagia. It can create a functional upper airway obstruction or respiratory distress through significant swelling and direct airway compression. CT is useful to confirm the diagnosis and extent of infection; treatment involves antibiotics, airway support, and admission for close monitoring. ENT and anesthesia consultants can help in planning and support if an emergent airway is required.

Clinical Features.  Epiglottitis is classically acute in onset. It is marked by high fever, intense sore throat, toxicity, and rapid progression. In one study, 85% of children with epiglottitis were symptomatic for less than 24 hours before seeking medical care.32 Children with epiglottitis appear anxious and maintain a “sniffing” or “tripod” position with the jaw jutting forward and the neck extended to maximize airway patency. As symptoms worsen, cough and phonation are usually absent. Drooling is prominent because of an inability to swallow.33 Singer and McCabe showed that in children younger than 24 months, toxicity, altered mental status, dyspnea, stridor, retractions, and fever are common initial symptoms.34 Losek and co-workers reported a series of 236 patients in which 7 patients (3%) died. In addition, the correct diagnosis of epiglottitis was not made in 11 of 58 children younger than 2 years (19%) and in 49 of 178 children between 2 and 18 years old (28%). Incorrect diagnoses in patients who died of epiglottitis included croup, summer virus, and pharyngitis. Croup was the most commonly assigned misdiagnosis and more often made in the setting of very young children or those in whom drooling and difficulty in swallowing were not prominent.32 The older patient is less likely to show dramatic signs of upper airway obstruction compared with the younger child because the diameter of the airway is larger and thus takes a greater degree of swelling to produce symptoms. Epiglottitis caused by bacteria other than H. influenzae tends to have a slower onset and is less likely to cause airway compromise. A majority of patients with H. influenzae epiglottitis were also found to have bacteremia (50-75%).35 Diagnostic Strategies.  Direct examination or manipulation of the pharynx should be avoided in cases in which epiglottitis is strongly suspected. A lateral neck radiograph can be helpful to confirm the diagnosis and should be evaluated for an enlarged epiglottis (“thumbprint sign”; Fig. 168-5), thickened aryepiglottic folds, lack of air in the vallecula, and dilated hypopharynx. Careful observation of a child with suspected epiglottitis is essential, and clinicians skilled in airway management should accompany the patient at all times. Laboratory tests, intravenous fluids and antibiotics, and blood and epiglottis cultures are all important considerations once the airway has been secured. Management.  The clinical features of classic epiglottitis are usually sufficiently characteristic that diagnostic tests are not

Epiglottitis Perspective.  Although it is still a feared pediatric emergency, acute epiglottitis has declined markedly in incidence since widespread administration of Haemophilus influenzae type b vaccine.2325 First licensed in 1985 for children 24 months old, the vaccine became available for immunization of infants 2 months of age in 1990. Principles of Disease.  Epiglottitis is an invasive bacterial disease that causes inflammation and edema of the epiglottis, aryepiglottic folds, arytenoids, and surrounding supraglottic tissues. As these structures become inflamed and distended, they protrude downward and over the glottic opening. Uncommon in the first year of life, epiglottitis was historically caused by H. influenzae type b in children 3 to 7 years of age and occurred year-round. This traditional profile has changed.26-28 In a survey of patients with epiglottitis since 1990, the average patient is older (80 vs. 35 months) with varying microbiology. H. influenzae type b is seen in a small minority of patients, and organisms such as group A betahemolytic streptococcus, S. aureus, and Streptococcus pneumoniae are more common.29 Noninfectious causes are rare and include thermal injury from swallowing of hot liquids.30,31

Figure 168-5.  Epiglottitis. Note the “thumbprint sign” of the epiglottis and thickened aryepiglottic folds.

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necessary and should be avoided so as not to agitate the patient. The importance of securing the airway takes precedence over diagnostic evaluation. A “stable” patient who is maintaining a patent airway and adequate oxygenation should not be moved or repositioned for examination, laboratory tests, or radiography. Such patients should be carefully transported to a setting where definitive airway management can be achieved in a controlled fashion, generally the operating room. If diagnostic studies are needed, constant and close observation is vital. Careful decision-making is essential when a child with epiglottitis or suspected epiglottitis requires transport. A survey of pediatric intensive care and emergency physicians reported that half recommended intubation before inter-hospital transport in all cases. The remainder individualized the recommendation for intubation before transport in part on the basis of the referring physician’s perceived ability to intubate the child.36 Unstable patients with respiratory failure require assisted ventilation. Bag-valve-mask ventilation should be attempted first and, if it is successful, continued until intubation can be performed by the emergency physician or anesthesiologist. If neither bag-valvemask ventilation nor intubation is successful, more aggressive techniques, such as needle cricothyroidotomy or tracheostomy, may be indicated. Regardless of the approach to securing the airway, it is prudent for the emergency physician to rapidly consult other experts in airway management, such as an anesthesiologist (fiberoptic intubation), ENT specialist, or general surgeon (surgical approaches), so that a plan of approach can be made and morbidity reduced. Once they are intubated, patients generally remain so for 3 to 5 days of antibiotic therapy to allow adequate decrease in epiglottic size and surrounding tissue edema. A second- or third-generation cephalosporin is appropriate.

Other Noninfectious Supraglottic Disease Trauma and Burns.  Thermal injury from facial burns and inhaled smoke or steam and trauma to the face and neck can create physical findings similar to infectious epiglottitis. Rapidly progressive stridor, drooling, an unwillingness to lie flat, and a swollen, inflamed epiglottis may occur. Some studies show a mortality around 20% in children with burn injuries when airway burns are also present. Toddlers are particularly prone to inhalation of hot liquids as they more independently eat and drink without initially

being attentive to temperature. Aspiration of hot liquids is the most common cause of airway burns in infants and young children.37 The initial physical examination of the oropharynx may be relatively normal. Elective securing of the airway is suggested when laryngeal edema is suspected as progression of symptoms and edema may occur during the hours immediately after the injury.16 Bronchodilators may help with bronchospasm; steroids are controversial and not routinely recommended for use. Allergic Reaction.  Acute allergic reactions may cause supraglottic edema with respiratory distress and stridor. Food is the most common precipitant in infants and children, with higher mortality noted in peanut allergies and in children with atopy or asthma. Anaphylaxis with respiratory compromise should immediately be treated with intramuscular (more rapid onset) injection of epinephrine 1:1000 solution at 0.01 mg/kg up to 0.3 mg. Intravenous epinephrine 1:10,000 can be considered for patients in shock with severe allergic reactions. Rapid administration of antihistamines, oxygen, nebulized bronchodilators, and steroids should follow. Early intubation may be needed. Repeated doses of epinephrine may be needed, and the use of racemic epinephrine may also be considered. All discharged patients should have injectable epinephrine (EpiPen 0.3 mg epinephrine); a referral to an allergist and a MedicAlert bracelet are recommended. An EpiPen Jr contains a dose of 0.15 mg of epinephrine and should be prescribed for children weighing less than 30 kg.

Diseases of the Larynx The larynx and vocal cords compose an important region in the airway that is often associated with airway disease causing obstruction. Many of these obstructing conditions are congenital lesions, including laryngomalacia, laryngeal web, and vocal cord paralysis. Acquired lesions include laryngeal papillomas.

Congenital Lesions Laryngomalacia, the most common cause of chronic stridor in infants,38,39 is a result of incomplete development of the supporting cartilage of the larynx. With inspiration, the long, floppy epiglottis, arytenoids, and aryepiglottic folds are drawn into the larynx and create a partial obstruction (Fig. 168-6). Baseline inspiratory stridor begins several weeks after birth and worsens with

Figure 168-6.  Laryngomalacia. Note the progressive obstruction with inspiration as the epiglottis and surrounding structures collapse into the glottic opening.

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anomaly, inflammation from infection, and trauma associated with prolonged intubation.

Congenital Lesions

Figure 168-7.  Large laryngeal web. supine positioning and increased respiratory effort (crying, URI). Laryngomalacia is rarely associated with significant respiratory distress, feeding difficulties, or failure to thrive. Most patients experience complete resolution of symptoms by 2 years of age. However, Richter and Thompson described late-onset laryngomalacia in a series of 17 older children who presented with feeding disorders (mean age, 3.3 years), sleep disorders (mean age, 6.3 years), and exercise-induced stridor (mean age, 15 years).40 Fiberoptic bronchoscopy is used to confirm the diagnosis and to identify the existence of coexisting or synchronous anomalies (such as subglottic stenosis and tracheomalacia). Vocal cord paralysis is the second most common cause of chronic stridor in infants. Bilateral vocal cord paralysis results in severe respiratory distress and stridor and is often associated with serious central nervous system abnormalities, such as Arnold-Chiari malformation. Unilateral vocal cord paralysis is most commonly left sided and related to traction on the left recurrent laryngeal nerve at birth or compression from mediastinal structures. Infants with unilateral vocal cord paralysis have a hoarse, weak cry. Stridor often worsens with distress and improves with positioning of the affected side down. A laryngeal web results from failure of complete canalization of the airway.41 Most webs lie between the cords and appear as a partial anterior fusion (Fig. 168-7). The spectrum of symptoms reflects the size of the web. Small webs may cause a hoarse, weak cry and mild stridor. Larger, more complete webs are associated with aphonia and severe respiratory distress.

Laryngeal Papillomas Laryngeal papillomas arise from the laryngeal epithelium and may result from perinatal or postnatal exposure to human papillomavirus. When papillomas are acquired in the prenatal period, hoarseness, abnormal cry, and inspiratory stridor commonly occur by 3 to 4 years of age. Symptoms can progress to severe respiratory distress as the lesions enlarge and obstruct the larynx. Ultrasonography has been described as a useful adjunct in the diagnosis and management of patients with airway papillomas.42

Subglottic Tracheal Diseases The subglottic trachea is the origin of the high-pitched inspiratory sound commonly associated with upper airway obstruction. The subglottic space is the narrowest part of the airway in children younger than 8 years and is completely surrounded by the cricoid ring. Such anatomy predisposes this part of the airway to obstruction. Subglottic narrowing or stenosis can result from a congenital

Congenital laryngotracheal (“subglottic”) stenosis is a result of a congenital defect in canalization of the subglottic trachea. Deformity of the cricoid ring is usually seen. Infants with severe stenosis have stridor at birth. Milder lesions may be asymptomatic until additional obstruction from infection or inflammation occurs. Subglottic stenosis is also an acquired condition that occurs after prolonged intubation or blunt trauma to the neck. A subglottic hemangioma is a less common cause of stridor and subglottic airway obstruction in infants. The infant is usually asymptomatic at birth, but stridor (which may be biphasic) and cough develop within the first few weeks to months of life. Symptoms generally peak at 6 months as a result of rapid growth of the infant and the hemangioma during the first months of life. Respiratory symptoms worsen with crying and agitation. Cutaneous hemangiomas are seen in approximately half of cases. Hemangiomas of the airway may be seen on plain film as an asymmetrical lesion along the tracheal air column.

Viral Croup Principles of Disease.  Croup (laryngotracheobronchitis) is the most common cause of upper airway distress and obstruction in childhood. It occurs most commonly in late fall, early winter, and spring, with a peak incidence at 2 years (range, 6 months to 6 years) of age. Rarely, viral croup is seen in older, healthy children. Parainfluenza virus type 1 accounts for about half of cases; parainfluenza virus types 2 and 3, respiratory syncytial virus, influenza A and B viruses, and rhinovirus are responsible for the remainder.43 Croup is caused by inflammation, exudate, and edema of the loosely adherent mucosal and submucosal tissues of the subglottic space. The inflamed mucosa expands into the airway lumen because the cricoid cartilage forms a complete cartilaginous (nonexpanding) ring in this part of the trachea. The actual incidence of croup is unknown. Most children will have an uncomplicated course, and many cases are managed without medical intervention. Only a small percentage of those who receive urgent care require hospitalization. Croup is recurrent in a small number of patients. A subset of children with croup have involvement of the lower airway and exhibit bronchoconstriction, lower airway edema, and atelectasis. Clinical Features.  Croup is most often diagnosed clinically. Children with typical croup have a constellation of symptoms, including a barky cough, hoarse voice, and high-pitched, inspiratory stridor. These findings usually follow a several-day prodrome of mild fever and URI symptoms. Scoring systems have been developed for assessment of croup and include an evaluation of worsening stridor, retractions, cyanosis, heart rate, and respiratory rate. Although a formal croup score is often not assigned in many clinical settings, the determination of mild, moderate, or severe croup should be based on careful evaluation of these five signs as well as mental status and air movement. Mild croup is characterized by an intermittent barky cough, stridor with agitation but not at rest, mild tachypnea, and tachycardia. A child with mild croup is minimally distressed and well hydrated and has normal mental status. Moderate croup is characterized by audible stridor at rest, worsening stridor with agitation, barky cough, and increased work of breathing (retractions, tachypnea, tachycardia). A patient with moderate croup may be fussy but is alert, interactive, and comforted by parents. Hypoxia is atypical in mild or moderate croup. When hypoxia is seen, it may signify concomitant lower respiratory disease, another disease process, or severe croup.

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Laboratory tests are nondiagnostic. Radiographic studies of the neck are useful when the diagnosis is in doubt, but they do not change management. The classic finding in croup is a tapered narrowing of the normal shouldered appearance of the subglottic trachea such that it has the appearance of a pencil or steeple. Management.  Glucocorticoids are the mainstay of treatment of croup, resulting in reduced symptoms, reduced need for aerosolized epinephrine, fewer readmissions to the emergency department (ED), and shorter hospital stays.44,45 Evidence for the use of routine steroids in croup was Geelhoed and Macdonald’s comparison of the experience at Princess Margaret Hospital for Children before and after steroids became mandatory in the treatment of croup in patients in the intensive care unit (ICU).46 Before 1989, less than 5% of ICU patients received steroids. At that time, an average of 11% were intubated yearly, and the total ICU days were 129 (yearly average). Beginning in 1989, every child admitted to the ICU received 0.6 mg/kg dexamethasone intramuscularly. The intubation rate declined to 1% (yearly average), and total ICU days dropped to 21 (yearly average). The role of oral, parenteral, and inhaled steroids in the treatment of croup has been well documented.44 Geelhoed and Macdonald demonstrated that oral dexamethasone in doses as small as 0.15 mg/kg is as effective as higher doses in decreasing the duration of symptoms and hospitalization.47 Steroids in patients with mild croup have also been shown to improve symptoms and to reduce the need for return to medical care.48 More recently, a Cochrane review of 38 randomized controlled trials (4299 patients) found treatment of croup with glucocorticoids to be associated with the following outcomes: shorter length of stay in the ED, fewer return visits, and decreased use of epinephrine.49 Budesonide is an inhaled steroid with potent topical antiinflammatory properties. A single dose (2 mg) of nebulized budesonide was shown to shorten ED length of stay, to decrease the rate of hospitalization, and to cause a more rapid improvement in symptoms in children with mild to moderate croup evaluated in the ED.45 Inhaled budesonide (2 mg per dose) was shown to be as effective as oral dexamethasone (0.6 mg/kg) in decreasing the duration of hospital stay, improving clinical symptoms, and decreasing the ongoing requirement for aerosolized epinephrine. Aerosolized epinephrine, either racemic epinephrine (containing d and l isomers) or l-epinephrine, acts on alpha-adrenergic receptors in the subglottic mucosa.50 Through vasoconstriction, epinephrine reverses edema and relieves acute symptoms in a subset of patients. It is a temporizing measure with a quick onset of action (within 10 minutes) and duration of effect between 1 and 2 hours. Racemic epinephrine has traditionally been preferred to l-epinephrine because the racemic mixture has been associated with fewer cardiovascular side effects. However, the l form of epinephrine is the active isomer and has the same degree of safety and efficacy as racemic epinephrine51; either form may be used. The “rebound” phenomenon of epinephrine is defined as recurrence or worsening of the patient’s pretreatment symptoms when aerosolized epinephrine wears off. This rebound is rarely clinically significant if steroids are given early in management.52 It has been demonstrated that many patients with moderate croup who are treated with steroids and epinephrine can be safely discharged from the ED after treatment.53 A retrospective study evaluating the policy of discharging selected patients after treatment with racemic epinephrine yielded favorable results. Of 50 patients discharged after the administration of epinephrine, none was subsequently hospitalized and only one required retreatment within 48 hours as an outpatient. Importantly, 92% were discharged on a regimen of steroids. The investigators recommend that children with moderate croup who have received aerosolized epinephrine can be safely discharged (1) after 2 hours of observation after administration of epinephrine, (2) if they are free of stridor and retractions, and (3) if they have access to follow-up

BOX 168-1 Croup: Indications for Admission Severe respiratory distress or failure Unusual symptoms (hypoxia, hyperpyrexia) Dehydration Persistence of stridor at rest after aerosolized epinephrine and steroids Persistence of tachycardia, tachypnea Complex past medical history (prematurity, pulmonary, cardiac disease)

care. They also recommend administration of steroids in these patients.54 The decision to discharge after administration of aerosolized epinephrine should also be based on the patient’s symptoms, such as dehydration, preexisting airway disease, and other congenital anomalies. Cool mist has been advocated as a useful therapy for croup symptoms but has not been demonstrated to improve outcomes. It is hypothesized to act by moistening thickened secretions, thereby making them easier to mobilize out of the airway. A metaanalysis by Moore and Little of three randomized controlled trials (135 patients) reported that administration of humidified air to children with mild to moderate croup did not improve croup scores. They concluded that there is insufficient evidence to support the routine use of this intervention.55 A small percentage of patients with croup require admission. The decision to admit a child with moderate croup is based on a number of factors: severity of symptoms at initial evaluation, persistence of respiratory distress, stridor at rest, oxygenation, response to treatment, hydration, history suggesting airway disease or recurrent croup, young age (