RESPIRATORY AIRWAY INFECTIONS

CROUP

Acute laryngitis, laryngotracheobronchitis (viral croup), and epiglottitis (bacterial croup) are acute inflammatory diseases, collectively called croup, and involve the upper airways. The most common and most serious risk of this group of diseases is obstruction of the airway. This risk is particularly important to remember when treating very young children because the airways of young child are narrower than the airways of older children and adults.

Etiology

Parainfluenza virus type I is the most common cause of viral croup (Table AI-1 for a list of other causes of viral croup and laryngitis). Haemophilus influenzae type b is the most common cause of epiglottitis (bacterial croup) (see Table AI-2 for a list of other causes of epiglottitis).

Manifestations

Acute laryngitis

Acute laryngitis begins as an upper respiratory infection, followed by dysphonia (hoarseness). Other symptoms may include odynophonia (pain when speaking), dysphagia (difficulty swallowing), odynophagia (pain when swallowing), sore throat, congestion, fatigue, and malaise.

Viral croup

Patients with viral croup or laryngotracheobronchitis have a fever (38–39°C), which is higher than occurs in laryngitis, and restlessness and air hunger, which is more severe than occurs in laryngitis. Croup begins with a prodromal mild upper respiratory infection with coryza, nasal congestion, sore throat, and cough that lasts 2–3 days; this is followed by hoarseness and a harsh, brassy, “bark-like” cough. Respiratory stridor usually occurs at night, often awakening the child from sleep.

Physical examination of the patient with croup may reveal minimal distress to severe respiratory failure due to airway obstruction. In mild cases, the results of the lung examination at rest usually are normal; however, mild expiratory wheezing may he heard during auscultation. Children with severe croup have primarily inspiratory stridor at rest with nasal flaring and suprasternal and intercostal retractions. Lethargy or agitation may be a result of hypoxemia. Other warning signs of severe respiratory disease are tachypnea, tachycardia out of proportion to the presence of fever, lethargy, pallor, and hypotonia (decreased muscle tone). The child may be unable to maintain adequate oral intake and may become dehydrated. Cyanosis is a late and ominous sign. Croup symptoms usually peak over 3–5 days and resolve within 4–7 days.

Epiglottitis

Epiglottitis is a medical emergency and risk of mortality is extremely high. Signs and symptoms include acute onset and fever, sore throat, hoarseness, and a barking cough. There is retraction of the suprasternal notch and stridor with every breath. The throat is inflamed, and the epiglottis is swollen, stiff, and a beefy red color and can be seen by direct laryngoscopy. The disease can progress rapidly resulting in toxicity, prostration, severe dyspnea, and cyanosis. The physician should be watchful for the dysphagia, dysphonia, drooling, and distress—the four D’s.

Epidemiology

• Person-to-person contact is the usual means of spread of all types of croup.

Viral croup and acute laryngitis

• Young children are most susceptible to viral croup, which typically occurs in children 6 months to 3 years of age, with the mean age being 18 months. Boys are more likely to develop croup than are girls.
• Viral croup has an annual peak incidence during the second year of life of 50 new cases per 1000 children. The incidence of viral croup decreases dramatically by 6 years of age.
• Viral croup occurs in late fall and early winter. The recurrence rate is 5%.
• Outcomes of viral croup depend of how ill the patient is, the age of the patient, and the adequacy of the treatment. Complications in severe cases include crusty exudates resulting in obstruction of the airways, segmental atelectasis, pneumothorax, obstructive mediastinal emphysema, and bronchopneumonia.
• Parainfluenza infections can cause viral croup anytime during the year. Influenza virus and respiratory syncytial virus infections tend to occur more frequently during the winter and early spring.
• Acute laryngitis usually occurs in persons aged 18–40 years of age. Although children are less likely to contract acute laryngitis, they can acquire the disease and are usually 3 years of age or older.
• Acute laryngitis is usually a mild self-limiting disease lasting 7–10 days.

Epiglottitis

• The Haemophilus influenzae type b (Hib) vaccine has significantly reduced the incidence of the disease from 10.9 per 10,000 to 0.63 cases per 100,000.
• H influenzae type b is still the most common cause of epiglottitis.
• The median age of patients with epiglottitis has increased from 35 months of age to 80 months of age. Prior to 1994, the disease was usually seen in children 2–7 years of age.
• The prevalence of epiglottitis in adults now surpasses the prevalence in children, which is due to the success of Hib vaccination of children.
• The morbidity and mortality of epiglottitis can be very high, with bacteremia often resulting in meningitis, septic arthritis, or osteomyelitis.

Pathogenesis

Children have narrower airways than adults, which results in an increased number of complications associated with viral croup and epiglottitis.

Viral infection of the upper airways causes inflammation and edema of the larynx in acute laryngitis, and viral infection in the larynx, trachea, and bronchi causes viral croup. Mucus is produced by the host and causes partial obstruction of the airway in both viral croup and acute laryngitis. Swelling of the vocal cords results in dysphonia. In viral croup, narrowing of the subglottic trachea in a child’s airway results in audible inspiratory stridor. As viral croup progresses, the lumen of the trachea becomes obstructed further by fibrous exudates. The barking cough that occurs in patients with viral croup is caused by inflammation in the larynx and trachea.

 Epiglottitis is a cellulitis of the epiglottis and the surrounding tissues. H influenzae type b colonizes the pharynx. The organisms then colonize the epiglottitis and enter the tissues of the epiglottitis through minor breaks in the mucosal surface. The organisms grow in the tissues and cause an inflammatory response that result in erythema and edema. A sore throat rapidly progresses to difficulty breathing, stridor, obstruction of the airways, and respiratory arrest. Local extension from the colonized nasopharynx through soft tissues is likely to be the cause of epiglottitis.

Diagnosis

Diagnosis of acute laryngitis is based on the clinical signs and symptoms of the patient (see manifestations). Viral croup is diagnosed by hoarseness, barking cough, and inspiratory stridor and retractions, which indicate airway obstruction (Table AI-3). A patient with viral croup will usually experience less restlessness and air hunger following treatment with racemic epinephrine or water-saturated air. These treatments do not have any affect on a patient with bacterial epiglottitis. The steeple sign seen in an anteroposterior neck radiograph is characteristic of viral croup. Viral cultures usually are not obtained.

The patient with epiglottitis should be handled with extreme care because airway closure can occur simply by placing a tongue depressor in the patient’s mouth to examine the throat. Examination of the larynx can irritate the patient and cause airway closure and asphyxiation. Equipment for an emergency tracheostomy should be available during examination of a patient suspected of having epiglottitis. If the patient has bacterial epiglottitis, the etiologic agent should be determined. H influenzae type b, the most common cause of epiglottis, does not grow on blood agar, therefore, throat swabs and smears should be cultured on blood agar and chocolate agar plates. In epiglottitis, H influenzae is often in the bloodstream; therefore blood cultures are helpful. A leukocytosis can be seen in the complete blood count (CBC). A positive thumb sign on lateral radiographs of the neck is diagnostic of epiglottitis.

Therapy and Prevention

Acute laryngitis is a self-limiting infection, and symptomatic therapy usually is all that is necessary. Treatment of viral croup requires maintenance of an adequate airway as follows.

Proper care and handling of the patient with epiglottitis can determine whether the patient lives or dies. Treatment of epiglottitis involves securing the patient’s airway by intubation and antibiotic therapy with ceftriaxone or cefuroxime. Children should be sedated when being intubated to prevent them from pulling out the tube.

The Hib vaccine is the capsular type b polysaccharide conjugated to the diphtheria toxoid, and it has drastically reduced the incidence of epiglottitis in the U.S. A child who has not received the Hib vaccine and who is exposed to a patient with epiglottitis should receive chemoprophylaxis with rifampin.