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Viral Croup: Current Diagnosis and Treatment

      Viral croup, a common illness in children, manifests with noisy, labored breathing. Parainfluenza viruses are the most common cause of croup; however, other causes including epiglottitis and bacterial tracheitis should be considered in the differential diagnosis. The diagnosis is primarily based on clinical findings; imaging studies may be useful in selected cases. Although most children recover from this self-limited illness with only minimal medical intervention, some are severely affected by laryngeal swelling and require respiratory support with analgesics, cool mist, corticosteroids, nebulized epinephrine, heliox, and, rarely, intubation. In this article, the current diagnostic and management strategies for viral croup are summarized.
      The croup syndrome is commonly defined as a hoarse voice, dry barking cough, inspiratory stridor, and a variable amount of respiratory distress that develops over a brief period. Acute viral laryngotracheobronchitis, the most common type of croup, is usually a benign selflimited disease, but even this illness can cause pronounced laryngeal obstruction. Other conditions can also cause laryngeal obstruction and must be recognized to ensure that appropriate therapy is instituted. Recurrent croup and various anatomic anomalies, which cause chronic stridor, are distinct problems that must be evaluated and treated differently than acute viral croup.

      EPIDEMIOLOGY

      Viral laryngotracheobronchitis is primarily a disease of children between 1 and 6 years of age; mean age is 18 months. In the United States, its peak incidence is about 5 cases per 100 children during the second year of life. Although most cases occur during the late fall and winter, croup can manifest at all times of the year. Boys tend to be affected more commonly than girls.
      • Marx A
      • Torok TJ
      • Holman RC
      • Clark Ml
      • Anderson U
      Pediatric hospitalizations for croup (laryngotracheobronchitis): biennial increases associated with human parainfluenza virus 1 epidemics.

      ETIOLOGY

      Parainfluenza viruses (types 1, 2, and 3) account for almost 75% of isolated viral agents and are responsible for the large midwinter outbreaks of illness. Adenovirus and respiratory syncytial virus can also cause sporadic cases of croup. Influenza A has been isolated from children with severe croup symptoms. Rarely, Mycoplasma pneumoniae has been isolated from children with croup.

      PATHOPHYSIOLOGY

      The viral infection begins in the nasopharynx and spreads to the respiratory epithelium of the larynx and trachea. Diffuse inflammation with erythema and edema develops in the tracheal walls, and the mobility of the vocal cords becomes impaired because of swelling. The narrowest part of a child's upper airway is the subglottic region, which is surrounded by a firm ring of cartilage. A small amount of edema will significantly restrict airflow in a child's airway. This narrowing of the airway leads to audible inspiratory stridor, and the swelling of the vocal cords results in a hoarse voice.

      CLINICAL PICTURE AND DIFFERENTIAL DIAGNOSIS

      Viral croup usually begins with mild symptoms of an upper respiratory infection-low—grade fever, runny nose, and mild cough. The child awakes from a nap or during the middle of the night with a barking cough and discomfort from a sore throat. Inspiratory stridor is often the symptom that alerts parents that the child does not have a cold.
      Although a child's symptoms at home may be alarming, findings on physical examination of the child in the emergency department are usually minimal. This outcome has led to the belief that cool night air alleviates symptoms, but it may be related to the variability of symptoms over time. Children with severe disease may have inspiratory and expiratory stridor as well as suprasternal and intercostal retractions. Some children will also have wheezing, but, on auscultation of the chest, no abnormalities will be detected. In addition to tachycardia and tachypnea, fever is usually present. The illness lasts 3 to 7 days but is usually most severe on the first and second nights.
      Several other problems can cause sudden onset of laryngeal obstruction. Spasmodic croup resembles laryngotracheobronchitis (Table 1), but no fever or associated infection of the upper respiratory tract is present. This diagnosis is made only in retrospect because the symptoms recur more than once.
      Table 1Differential Diagnosis of the Croup Syndrome
      • Acute laryngotracheobronchitis
      • Spasmodic croup
      • Epiglottitis
      • Bacterial tracheitis
      • Peritonsillar abscess
      • Retropharyngeal abscess
      • Diphtheria
      • Angioneurotic edema
      • Burns or thermal injury
      • Smoke inhalation
      • Neoplasm or hemangioma
      • Foreign body
      • Acute laryngeal fracture
      • Arnold-Chiari malformation
      • Dandy-Walker malformation
      • Laryngomalacia
      • Subglottic stenosis
      • Laryngeal papillomatosis
      • Extrinsic obstruction by a vascular ring
      Epiglottitis is a bacterial cellulitis of the periepiglottic tissues. Like croup, this disease has a sudden onset, but, classically, this condition progresses rapidly to a toxic state. Epiglottitis is serious because the edema and swelling of the airway can progress to occlusion within a brief time; thus, diagnosis and airway stabilization must be established quickly. Before immunization was widely available, hemophilus influenza type B was the most common cause of epiglottitis. Although other respiratory bacteria such as Streptococcus pneumoniae can cause a similar cellulitis, the incidence of epiglottitis has decreased dramatically, and this condition is now rarely seen in children.
      The toxic symptoms of sudden onset of high fever, painful swallowing, anxiety, and aphonia should readily distinguish epiglottitis from viral laryngotracheobronchitis, but this distinction is not always possible. Direct visualization of the epiglottis in a controlled setting must be done in children with croup who have symptoms suggestive of epiglottitis.
      • Mauro RD
      • Poole SR
      • Loekhart CM
      Differentiation of epiglottitis from laryngotracheitis in the child with stridor.
      Bacterial tracheitis is an infection in which the supraglottic area appears normal, but the tracheal mucosa is ulcerated or necrotic with thick purulent exudate. This illness can begin with a prodrome resembling viral croup that progresses with high fever, toxicity, and respiratory distress, for which intensive airway management is needed. Bacterial tracheitis is considered a bacterial superinfection of an initial viral infection. Staphylococcus aureus is the most common bacterial pathogen. The diagnosis should be suspected when a child with upper airway distress does not respond to conventional therapy or when the condition of a child with croup deteriorates rather than improves in the expected time frame. Endoscopy may be needed to make the diagnosis.
      • Sendi K
      • Crysdale WS
      • Yoo J
      Tracheitis; outcome of 1,700 cases presenting to the emergency department during two years.

      DIAGNOSTIC TECHNIQUES

       Radiographic Studies

      Plain films of the soft tissues of the neck may show the classic radiologic steeple sign, with a narrowed air column in the subglottic area seen on the posteroanterior view. The hypopharynx may be overdistended on the lateral view. These findings are present in only 50% of cases of croup, and many children with clinical signs of croup have normal findings on radiography. In some children with early epiglottitis, the epiglottis will appear abnormal radiologically before respiratory compromise is apparent clinically. In a child with a foreign body such as an unsuspected coin in the esophagus, radiographic studies may be diagnostic. Radiographic findings, however, do not correlate well with clinical measures of severity of croup, and radiographic studies should be limited to children whose illness is atypical of laryngotracheobronchitis and whose respiratory status is stable.
      Rapid computed tomographic scanning of the neck has been suggested as a highly sensitive imaging modality that can provide clues to specific diagnoses. In the appropriate clinical setting, a computed tomographic scan may be more useful than plain films.
      • Rencken I
      • Patton WL
      • Brasch RC
      Airway obstruction in pediatric patients; from croup to BOOP.

       Pulse Oximetry

      Because laryngotracheobronchitis is a disease of the larger upper airway, alveolar gas exchange is usually normal Hypoxia and low oxygen saturation will be undetectable until a patient's condition is severe. A child with bronchospasm may have a lower than expected oxygen saturation, but most symptomatic children with croup will have normal findings on pulse oximetry. If methods of measuring hypercarbia become as readily accessible as those for determining oxygen saturation, quantification of the severity of the ventilation disorder in patients with croup may be possible by measuring partial pressure of carbon dioxide. Unfortunately, this technology is not yet readily available in the emergency setting.

       Laryngoscopy

      Although most children with croup do not require intubation or direct visualization of their airways, every facility that treats acute illnesses must have a plan for management of acute upper airway obstruction. In a child whose illness is severe, who has symptoms suggestive of epiglottitis, or whose condition fails to follow the anticipated benign course of croup, direct airway visualization may be necessary. In every child with imminent airway obstruction, airway visualization and intubation are necessary in a controlled setting.
      Direct inspection of the epiglottis occurs inadvertently during the usual physical examination of the pharynx in many children. Although sudden airway obstruction in children with acute epiglottitis is a possibility, this is probably not a concern in those with early epiglottitis. Airway obstruction is more likely to be part of the natural course of epiglottitis as cellulitis and airway swelling progress. Although direct visualization of the epiglottis is not advisable in a child with obvious respiratory distress, such an approach can be helpful in the diagnosis of acute epiglottitis in children whose symptoms are still mild during the early stages of the disease. In multiple studies, the presence of epiglottitis has been confirmed by direct visualization of the epiglottis in children whose clinical status did not suggest this bacterial infection; furthermore, airway obstruction did not occur.
      The airway of a child who has a history of choking or gagging at the onset of illness should be inspected for a possible foreign body. Laryngoscopy should be considered in children with croup whose illness does not resolve as expected, those who have noisy breathing or abnormal voice between episodes of croup, those who have frequent episodes or progressively more severe episodes of croup, and those who were intubated during the neonatal period and thus may have subglottic stenosis or laryngeal nerve injury. Abnormal findings that have been described in such patients include subglottic hemangiomas, laryngeal polyps, and vocal cord paralysis.

      CLINICAL COURSE

      The vast majority of children with croup have a benign self-limited illness that persists for 3 to 7 days. With the advent of nebulizer therapy, only a few children examined in the emergency department will require inpatient care. For children in whom hospitalization is necessary, less than 5% require intubation, and good airway support has reduced the mortality and morbidity associated with this illness. A croup severity score (Table 2) developed as a research tool by Westley and associates' can be helpful in assessing the initial severity of croup and may also help in monitoring the child's response to treatment.
      Table 2Scoring System for Croup, Based on Five Clinical Signs
      * Zero represents the normal state or absence of the sign, and the highest number represents the most severe distress.
      From Westley and associates.
      • Westley CR
      • Cotton EK
      • Brooks JG
      Nebulized racemic epinephrine by IPPB for the treatment of croup: a double-blind study.
      By permission.
      Level of consciousness
       Normal or sleeping0
       Disoriented5
      Cyanosis
       None0
       With agitation4
       At rest5
      Stridor
       None0
       With agitation1
       At rest2
      Air entry Normal0
       Decreased1
       Markedly decreased2
      Retractions
       None0
       Mild1
       Moderate2
       Severe3
      * Zero represents the normal state or absence of the sign, and the highest number represents the most severe distress.
      Complications of croup are commonly related to the upper respiratory tract. Otitis media can occur, even in children not susceptible to this problem. Pneumonia is an uncommon complication. Because of pain during swallowing, some children will have decreased fluid intake, and thus dehydration is a possibility.

      TREATMENT

      The mainstay of treatment of croup is airway management. Symptomatic relief of a dry sore throat is sufficient for most children. Those with moderate to severe croup will need active airway management in the emergency department and may require inpatient care.

       Analgesics

      Simple measures such as orally administered analgesics will help many children with mild or moderate croup to continue oral intake and maintain hydration. A standard dose of acetaminophen, 10 to 15 mg/kg, or ibuprofen, 10 mg/kg, will usually be beneficial.

       Cool Mist and Oral Intake

      Since the 19th century, mist treatment has been used to relieve croup symptoms.
      • Henry R
      Moist air in the treatment of laryngotracheitis.
      Cool mist is as effective as hot steam, and the risk of burns from hot water is avoided. At home, parents can help their child by sitting in a bathroom while water flows from the showerhead.
      Cool mist moistens secretions and soothes inflamed mucosa. In addition, humidity decreases the viscosity of tracheal mucus secretions. Cool mist, however, can aggravate bronchospasm in children who are prone to wheezing. If the mist is delivered by means of a “croup tent,” signs of increasing respiratory distress may be overlooked because of the “foggy air.” Moreover, separation of the child from his parents is anxiety provoking and may increase respiratory distress. Cool mist vapor delivered by aerosol while the child sits on the parent's lap is the delivery system best tolerated by young children. Drinking liquids or eating Popsicles may be beneficial. In rare situations, a child's decreased oral intake leads to dehydration, and intravenous therapy is needed to maintain circulation until oral intake is possible.

       Nebulized Epinephrine

      For more than 20 years, aerosolized epinephrine has been used to treat severe croup symptoms. As use of this treatment has increased, tracheotomy for croup has virtually become nonexistent. Initially, epinephrine in racemic form was administered by intermittent positive pressure. Investigators now know that racemic epinephrine, a 1:1 mixture of the d-isomer and l-isomer of adrenaline, and the more readily available l-epinephrine are equally efficacious. Additionally, it is clear that the medication can be given by nebulizer rather than by intermittent positive pressure breathing.
      The mechanism of action of aerosolized epinephrine is thought to be stimulation of a-adrenergic receptors and subsequent constriction of capillary arterioles; thus, the fluid does not exude into laryngeal tissues. Decreased laryngeal mucosal edema will increase the diameter of the airway. Symptoms of inspiratory stridor and intercostal retractions will decrease as respiratory effort becomes less labored. The effect of aerosolized epinephrine is brief. Although its benefits may last for 2 hours, some children have recurrence of inspiratory stridor much sooner. In most children treated with aerosolized epinephrine, one treatment is effective; however, a child should not be dismissed from the emergency department until 3 hours after treatment, with no recurrence of retractions.
      In determining which children to treat with aerosolized epinephrine, physicians should remember that croup is usually a self-limited condition, even when a child's breathing is noisy. A study of 305 children with stridor at rest but no retractions showed that only 1% needed more than cool mist for treatment. When studies in which aerosolized epinephrine is used for children with stridor are compared with studies in which children do not receive epinephrine, improvement in the child's condition and time spent in the emergency department are similar. The children who were treated with epinephrine might have experienced improvement, even without this therapy.
      • Prendergast M
      • Jones JS
      • Hartman D
      Racemic epinephrine in the treatment of laryngotracheitis: can we identify children for outpatient therapy?.
      Aerosolized epinephrine should be reserved for children with croup who are severely ill, those needing intubation, those who have respiratory compromise in conjunction with retractions, and those whose stridor does not respond to cool mist and analgesics. A dose of 0.25 to 0.75 mL of 2.25% racemic epinephrine solution in 2.5 mL of normal saline can be given as often as every 20 minutes. If racemic epinephrine is not available, a 5-mL mixture of l-epinephrine and saline (1:100) may may be used in the nebulizer. Because of possible adverse effects, aerosolized epinephrine should be used cautiously if the child has tachycardia, a heart condition such as tetralogy of Fallot, or ventricular outlet obstruction.

       Corticosteroids

      Corticosteroids have been proposed for the treatment of croup because the reduced vascular permeability should result in decreased laryngeal swelling. Clinical trials have demonstrated clear improvement in children with severe croup treated with corticosteroids in comparison with children who received placebo. Clinically detectable effects are not as readily apparent in children with mild or moderate croup because they are likely to recover regardless of treatment.
      Initial studies showed the greatest improvement in children who received a single parenterally administered dose of dexamethasone of 0.6 mg/kg (maximal dose, 10 mg).
      • Super DM
      • Cartelli NA
      • Brooks Li
      • Lembo RM
      • Kumar ML
      A prospective randomized double-blind study to evaluate the effect of dexamethasone in acute laryngotracheitis.
      This continues to be the standard dose. Because dexamethasone has a long half-life, the single dose should provide treatment effects that extend through the severe, early stage of the illness. Oral dexamethasone therapy at a dose of 0.6 mg/kg also seems to be effective in reducing croup symptoms.
      • Klassen TP
      • Craig WR
      • Moher D
      • Osmond MH
      • Pasterkamp H
      • Sutcliffe T
      • et al.
      Nebulized budesonide and oral dexamethasone for treatment of croup: a randomized controlled trial.
      Budesonide, a nebulized corticosteroid, has been studied in acute croup and seems to have a rapid, beneficial effect in children with moderate to severe croup. This medication is not yet available in the United States. A report of fluticasone by metered-dose inhaler showed no effect in children with mild to moderate croup. Currently, in the United States, inhaled corticosteroids do not seem to have a clear role in the management of croup.

       Heliox

      The efficacy of heliox, a mixture of helium and oxygen, for the management of severe croup has been recognized for more than 20 years. This combination reduces the work of breathing by improving laminar gas flow through the obstructed airway. In children with severe croup, blood oxygenation will be improved when heliox rather than plain increased oxygen is used. Moreover, with use of heliox, intubation may be unnecessary, and the time frame for nebulized epinephrine and corticosteroids to reduce laryngeal swelling is extended.
      • McGee DL
      • Ward DA
      • Hinchliffe S
      Helium-oxygen therapy in the emergency department.

       Intubation

      Rarely, analgesics, mist, nebulized epinephrine, corticosteroids, and heliox fail in the treatment of croup. In this setting, the child requires endotracheal intubation and management in a pediatric intensive-care unit. The decision to intubate is based on clinical criteria that indicate that hypercarbia and respiratory failure have developed. Because of laryngeal swelling, an endotracheal tube two sizes smaller than that used for the healthy child will be needed to prevent pressure necrosis and subsequent subglottic stenosis. Intubation is usually necessary only for a brief period until laryngeal edema resolves.

       Summary

      The following points summarize the treatment of croup. (1) Mild croup with no stridor and minimal distress can be safely treated at home with analgesics, hydration, and cool mist. (2) Moderate croup with stridor at rest but no retractions and no distress can be treated with oral analgesics, cool mist, and dexamethasone. Children with this type of croup should be observed in the emergency department. If chest retractions do not develop and if close follow-up is possible, most children can be dismissed home. (3) Moderate croup with stridor at rest and retractions should be treated initially with analgesics, cool mist, and dexamethasone. If no improvement occurs within a brief period, nebulized epinephrine should be used. Although almost one-half of children with these symptoms will require repeated epinephrine treatments, many will experience relief of discomfort after a single treatment and can be dismissed from the emergency department if retractions do not recur after 3 hours of observation. (4) Severe croup should be treated with nebulized epinephrine initiated rapidly while arrangements are made for endotracheal intubation or transfer of the child to a pediatric intensivecare unit.

      CONCLUSION

      Viral croup is an acute self-limited disease of the upper airway in a child, characterized by barking cough, inspiratory stridor, hoarse voice, and upper respiratory symptoms. Croup is diagnosed by clinical signs and symptoms. If no immediate airway management is needed, radiography of the neck may help to exclude other entities that cause laryngeal obstruction. Pulse oximetry is an incomplete method of monitoring upper airway obstruction. Direct visualization of the epiglottis in the emergency department is a safe and useful procedure in a child whose condition is stable and who has no symptoms suggesting epiglottitis. Visualization of the airway with use of anesthesia should be done immediately in the following situations: when croup is severe enough that intubation is necessary, when epiglottitis is strongly considered, and when a foreign body may be in the respiratory tract. Laryngoscopy should be considered in children whose illness has an atypical history, such as recurrent episodes, or when the illness does not resolve as expected. All children with croup should receive analgesics and hydration as initial treatment. Corticosteroids to reduce inflammation are effective in the immediate management of croup. Nebulized epinephrine therapy should be used when children with inspiratory stridor at rest also have retractions that do not respond rapidly to analgesics and hydration. Inpatient care will be needed for children with severe respiratory distress, those who need repeated epinephrine nebulization, children with poor oral intake, those with unreliable caretakers, and children who live a considerable distance from medical care.

      References

        • Marx A
        • Torok TJ
        • Holman RC
        • Clark Ml
        • Anderson U
        Pediatric hospitalizations for croup (laryngotracheobronchitis): biennial increases associated with human parainfluenza virus 1 epidemics.
        J Infect Dis. 1997; 176: 1423-1427
        • Mauro RD
        • Poole SR
        • Loekhart CM
        Differentiation of epiglottitis from laryngotracheitis in the child with stridor.
        Am J Dis Child. 1988; 142: 679-682
        • Sendi K
        • Crysdale WS
        • Yoo J
        Tracheitis; outcome of 1,700 cases presenting to the emergency department during two years.
        J Otolaryngol. 1992; 21: 20-24
        • Rencken I
        • Patton WL
        • Brasch RC
        Airway obstruction in pediatric patients; from croup to BOOP.
        Radiol Clin North Am. 1998 Jan; 36: 175-187
        • Westley CR
        • Cotton EK
        • Brooks JG
        Nebulized racemic epinephrine by IPPB for the treatment of croup: a double-blind study.
        Am J Dis Child. 1978; 132: 484-487
        • Henry R
        Moist air in the treatment of laryngotracheitis.
        Arch Dis Child. 1983; 58: 577
        • Prendergast M
        • Jones JS
        • Hartman D
        Racemic epinephrine in the treatment of laryngotracheitis: can we identify children for outpatient therapy?.
        Am J Emerg Med. 1994; 12: 613-616
        • Super DM
        • Cartelli NA
        • Brooks Li
        • Lembo RM
        • Kumar ML
        A prospective randomized double-blind study to evaluate the effect of dexamethasone in acute laryngotracheitis.
        J Pediatr. 1989; 115: 323-329
        • Klassen TP
        • Craig WR
        • Moher D
        • Osmond MH
        • Pasterkamp H
        • Sutcliffe T
        • et al.
        Nebulized budesonide and oral dexamethasone for treatment of croup: a randomized controlled trial.
        JAMA. 1998; 279: 1629-1632
        • McGee DL
        • Ward DA
        • Hinchliffe S
        Helium-oxygen therapy in the emergency department.
        J Emerg Med. 1997; 15: 291-296

      Questions About Viral Croup

      (See article, pages 1102 to 1106)
      • 1.
        Which one of the following organisms is most likely to cause laryngotracheobronchitis?
        • a.
          Parainfluenza viruses, types 1, 2, and 3
        • b.
          Hemophilus influenza
        • c.
          Group A β-hemolytic streptococcus
        • d.
          Adenovirus
        • e.
          Branhamella catarrhalis
      • 2.
        Which one of the following statements is a correct interpretation of the use of radiography in the assessment of a child with acute upper airway illness?
        • a.
          No radiographic studies should be performed because the condition of such children can deteriorate quickly, and transporting them to the radiology department could be life threatening
        • b.
          Radiography of the soft tissue of the lateral aspect of the neck will always detect epiglottitis
        • c.
          A radiographic study that shows narrowing of the upper airway always indicates clinically severe illness
        • d.
          If no immediate airway management is necessary, radiography of the neck can be a preliminary tool for excluding unusual entities causing croup
        • e.
          A radiographic study that shows epiglottitis always indicates that the child must undergo direct laryngoscopy
      • 3.
        Which one of the following is not helpful in the management of viral croup?
        • a.
          Analgesics
        • b.
          Corticosteroids
        • c.
          Antibiotics
        • d.
          Cool mist
        • e.
          Nebulized epinephrine
      • 4.
        Which one of the following doses of medications would be inappropriate in the treatment of viral croup?
        • a.
          0.6 mg/kg of dexamethasone administered intramuscularly
        • b.
          0.06 mg/kg of dexamethasone administered intramuscularly
        • c.
          0.6 mg/kg of dexamethasone administered orally
        • d.
          Ten to 15 mg/kg of acetaminophen administered orally
        • e.
          0.25 to 0.75 mL of 2.25% racemic epinephrine administered by nebulizer
      • 5.
        Which one of the following is a contraindication to home management of a child with croup?
        • a.
          Child demonstrates that he is able to drink fluids
        • b.
          Child is staying with a 16-year-old caretaker for the weekend
        • c.
          Child has no retractions and no stridor at rest
        • d.
          Child has a temperature of 38°C
        • e.
          Child has a past history of recurrent pneumonia, but hospitalization has never been necessary

      Correct answers: 1. a, 2. d, 3. c, 4. b, 5. b