Croup

Question 1

What is croup?

Answer 1

Croup is a common, primarily pediatric viral respiratory tract illness. As its alternative names, acute laryngotracheitis and acute laryngotracheobronchitis, indicate, croup generally affects the larynx and trachea, although this illness may also extend to the bronchi. This respiratory illness, recognized by physicians for centuries, derives its name from an Anglo-Saxon word, kropan, or from an old Scottish word, roup, meaning to cry out in a hoarse voice.

Question 2

What are the signs and symptoms of croup?

Answer 2

Croup is the most common etiology for hoarseness, cough, and onset of acute stridor in febrile children. Symptoms of coryza may be absent, mild, or marked. The vast majority of children with croup recover without consequences or sequelae; however, it can be life-threatening in young infants.

Question 3

What respiratory symptoms suggest croup?

Answer 3

Croup manifests as hoarseness, a seal-like barking cough, inspiratory stridor, and a variable degree of respiratory distress. However, morbidity is secondary to narrowing of the larynx and trachea below the level of the glottis (subglottic region), causing the characteristic audible inspiratory stridor

Question 4

What are the characteristics of stridor in croup?

Answer 4

Stridor is a common symptom in patients with croup. [1] Acute onset of this abnormal sound in a child alarms parents and caregivers, enough to prompt an urgent care or emergency department (ED) visit. Stridor is an audible harsh, high-pitched, musical sound on inspiration produced by turbulent airflow through a partially obstructed upper airway. This partial airway obstruction can be present at the level of the supraglottis, glottis, subglottis, and/or trachea. During inspiration, areas of the airway that are easily collapsible (eg, supraglottic region) are suctioned closed because of negative intraluminal pressure generated during inspiration. These same areas are forced open during expiration.

Question 5

What do the physical findings of stridor indicate in patients with croup?

Answer 5

Depending on timing within the respiratory cycle, stridor can be heard on inspiration, expiration, or in both (biphasic; inspiratory and expiratory). Inspiratory stridor suggests a laryngeal obstruction, whereas expiratory stridor suggests tracheobronchial obstruction. Biphasic stridor indicates either a subglottic or glottic anomaly. An acute onset of marked inspiratory stridor is the hallmark of croup; however, concurrently there may be a less audible expiratory stridor.

Question 6

What is the etiology of croup?

Answer 6

Viruses causing acute infectious croup are spread through either direct inhalation from a cough and/or sneeze, or by contamination of hands from contact with fomites with subsequent touching the mucosa of the eyes, nose, and/or mouth. The most common viral etiologies are parainfluenza viruses. The type of parainfluenza (1, 2, and 3) virus causing croup outbreaks varies each year.

Question 7

How is croup transmitted?

Answer 7

The primary ports of viral entry are the nose and nasopharynx. The infection spreads and eventually involves the larynx and trachea. The lower respiratory tract may also be affected, as in acute laryngotracheobronchitis. Some practitioners feel that with lower airway involvement, further diagnostic evaluation is warranted to address concern for a secondary bacterial infection.

Question 8

Which physical findings suggest croup?

Answer 8

Inflammation and edema of the subglottic larynx and trachea, especially near the cricoid cartilage, are most clinically significant. Histologically, the involved area is edematous, with cellular infiltration located in the lamina propria, submucosa, and adventitia. The infiltrate contains lymphocytes, histiocytes, neutrophils and plasma cells. Parainfluenza virus activates chloride secretion and inhibits sodium absorption across the tracheal epithelium, contributing to airway edema. The anatomical area impacted is the narrowest part of the pediatric airway; accordingly, swelling can significantly reduce the diameter, limiting airflow. This narrowing results in the seal-like barky cough, turbulent airflow, stridor, and chest wall retractions. Endothelial damage and loss of ciliary function also occur. A mucoid or fibrinous exudate partially occludes the lumen of the trachea. Decreased mobility of the vocal cords due to edema leads to the associated hoarseness.

Question 9

What is the disease course of severe croup?

Answer 9

In severe disease, fibrinous exudates and pseudomembranes may develop, causing even greater airway obstruction. Hypoxemia may occur from progressive luminal narrowing and impaired alveolar ventilation and ventilation-perfusion mismatch.

Question 10

What is the most common cause of croup?

Answer 10

Parainfluenza viruses (types 1, 2, 3) are responsible for about 80% of croup cases, with parainfluenza types 1 and 2, accounting for nearly 66% of cases. Type 3 parainfluenza virus causes bronchiolitis and pneumonia in young infants and children. Type 4 parainfluenza virus, with subtypes 4A and 4B, is not as well understood and tends to be associated with a milder clinical illness.

Question 11

What are the signs and symptoms of croup?

Answer 11

Croup usually begins with nonspecific respiratory symptoms (ie, rhinorrhea, sore throat, cough). Fever is generally low grade (38-39°C) but can exceed 40°C. Within 1-2 days, the characteristic signs of hoarseness, barking cough, and inspiratory stridor develop, often suddenly, along with a variable degree of respiratory distress. Symptoms are perceived as worsening at night, with most emergency room visits occurring between the hours of 10 pm and 4 am. Symptoms typically resolve within 3-7 days, but can last as long as 2 weeks.

Question 12

Which clinical findings suggest croup?

Answer 12

The clinical presentation of croup has wide variation. Most children have just a “croupy” cough and hoarse cry. Some may have stridor only upon activity or agitation, whereas others may have audible stridor at rest and clinical evidence of respiratory distress. Overall however, a child with croup typically does not appear toxic. Paradoxically, a child with a severe case of croup may have “quiet” stridor due to a significant degree of airway obstruction.

Question 13

What is the Westley score for assessing severity of croup?

Answer 13

Croup scores have been developed to assist the clinician in assessing the patient’s degree of respiratory compromise. A commonly cited croup severity rating score is called the Westley score. Although widely used for research purposes and for the evaluation of treatment protocols, its clinical application has not been extensively studied. The Westley score evaluates the severity of croup by assessing five factors: level of consciousness, cyanosis, stridor, air entry, and retractions. The point values given for each factor are listed below, and the final score sum has a range of 0 to 17.

Level of consciousness: Normal, including sleep - 0 points, Depressed - 5 points

Cyanosis: None - 0 points, Upon agitation - 4 points, At rest - 5 points

Inspiratory stridor: None - 0 points, Upon agitation - 1 point, At rest - 2 points

Air entry: Normal - 0 points, Mild decrease - 1 point, Marked decrease - 2 points

Retractions: None - 0 points, Mild - 1 point, Moderate - 2 points, Severe - 3 points

Question 14

How is croup severity classified with the Westley rating system?

Answer 14

With the Westley rating system, a sum score of less than 2 indicates mild disease. Mild disease is defined as an occasional barking cough, hoarseness, no stridor at rest, and mild or absent suprasternal or subcostal retractions. The majority (about 85%) of children who present to the emergency department have mild croup. A sum score of 3-5 indicates moderate disease. Moderate disease findings include frequent cough, audible stridor at rest, and visible retractions, but little distress or agitation. Severe disease is indicated with a sum score range of 6-11. Patients present with prominent inspiratory (and, occasionally, expiratory) stridor, frequent cough, marked chest wall retractions, decreased air entry on auscultation, significant distress and agitation. Fortunately, severe croup is rare. A sum Westley score of ≥ 12 indicates impending respiratory failure. At this point, a barking cough and stridor may no longer be prominent. Lethargy, cyanosis, and decreasing retractions are harbingers of impending respiratory failure.

Question 15

What is the Alberta Clinical Practice Guideline scale for croup severity?

Answer 15

Another clinically useful croup severity assessment rating system has been developed by the Alberta Clinical Practice Guideline Working Group. [15, 16] By following this classification scheme, 21 different general emergency rooms in Alberta, Canada diagnosed 85% of children to have mild croup, and less than 1% with severe croup. The assessment tool used was as follows:

Mild severity - Occasional barking cough, no audible stridor at rest, and either no or mild suprasternal and/or intercostal retractions

Moderate severity - Frequent barking cough, easily audible stridor at rest, and suprasternal and sternal wall retractions at rest, with no or minimal agitation

Severe severity - Frequent barking cough, prominent inspiratory (and occasionally expiratory) stridor, marked sternal wall retractions, significant agitation and distress

Impending respiratory failure - Barking cough (often not prominent), audible stridor at rest, sternal wall retractions may not be marked, lethargy or decreased consciousness, and often dusky appearance without supplemental oxygen support

Question 16

How is croup diagnosed?

Answer 16

Croup is primarily a clinical diagnosis, with the diagnostic clues based on presenting history and physical examination findings.

Question 17

What is the role of lab testing in the diagnosis of croup?

Answer 17

Laboratory test results rarely contribute to confirm diagnosis. The complete blood cell (CBC) count is usually nonspecific, although the white blood cell (WBC) count and differential may suggest a viral etiology with lymphocytosis. Identifying the specific viral etiology (eg, parainfluenza virus type) via nasal washings is typically not necessary, but may be useful to determine isolation needs in the hospital care setting or, in the case of influenza A, to decide whether antiviral therapy should be initiated.

Question 18

When is an evaluation of hydration status or IV fluid support indicated for children with croup?

Answer 18

Patients who present with fevers, tachypnea, and history of decreased oral fluid intake require evaluation of their hydration status. Compromised oral intake and inability to maintain needed fluid volume may require intravenous fluid support to stabilize, support, and sustain fluid requirements.

Question 19

What is the role of radiography in the diagnosis of croup?

Answer 19

Plain films can verify a presumptive diagnosis or exclude other disorders causing stridor and hence, mimic croup. A lateral neck radiograph can help detect clinical diagnoses such as an aspirated foreign body, esophageal foreign body, congenital subglottic stenosis, epiglottitis, retropharyngeal abscess or bacterial tracheitis (thickened trachea).

Most importantly, croup is a clinical diagnosis. Radiographs can be used as a tool to help confirm this diagnosis, but are not required in uncomplicated cases. The anteroposterior (AP) radiograph of the soft tissues of the neck classically reveals a steeple sign (also known as a pencil-point sign), which signifies subglottic narrowing, whereas the lateral neck view may reveal a distended hypopharynx (ballooning) during inspiration (see the images below). However, these x-ray findings may not be seen in up to 50% of children with clinical symptoms of croup.

A steeple sign may also be observed in patients without croup, which warrants other differential considerations for this radiographic finding, such as epiglottitis, thermal injury, angioedema, or bacterial tracheitis. Patients should be monitored during imaging, because progression toward airway obstruction may occur rapidly.

Question 20

How should a medical exam of a child with croup and significant respiratory distress be conducted?

Answer 20

Any infant/child who presents with significant respiratory distress/complaints with stridor at rest must have a thorough medical evaluation to ensure the patency of the airway and maintenance of effective oxygenation and ventilation. Young children should be kept as comfortable as possible, allowing him or her to remain in a parent’s arms and avoiding unnecessary painful interventions that may cause agitation, respiratory distress, and lead to increased oxygen requirements. Persistent crying increases oxygen demands, and respiratory muscle fatigue can worsen the airway obstruction.

Question 21

What monitoring is needed for severe croup?

Answer 21

Concurrently, careful monitoring of heart rate (for tachycardia), respiratory rate (for tachypnea), respiratory mechanics (for sternal wall retractions), and pulse oximetry (for hypoxia) are important. Given the risk of increased insensible losses from fever, tachypnea and a history of decreased oral intake, assessment of the patient’s hydration status is imperative.

Question 22

Which treatments for croup should be administered in urgent care clinics or emergency departments (ED)?

Answer 22

Current treatment approaches in the urgent care clinics or emergency departments are corticosteroids and nebulized epinephrine; steroids have proven beneficial in severe, moderate, and even mild croup. In the straightforward cases of croup, antibiotics are not prescribed, as the etiology is viral. Lack of improvement or worsening of symptoms can be due to a secondary bacterial process, which requires the use of antimicrobials for treatment. Typically, patients with a bacterial component would have had moderate-to-severe croup assessment scores, requiring inpatient care and observation.

Question 23

How should severe respiratory distress or compromise from croup be treated?

Answer 23

Infants and children with severe respiratory distress or compromise may require oxygenation with ventilation support, initially with a bag-valve-mask device. If the airway and breathing require further stabilization due to increasing respiratory fatigue and hence, worsening hypercarbia, (as evident by ABG), the patient should be intubated with an endotracheal tube. Intubation should be accomplished with an endotracheal tube that is 0.5-1 mm smaller than predicted. Once airway stabilization is achieved, these patients are transferred for their ongoing care to a pediatric intensive care unit.

Question 24

What is the role of corticosteroids in the treatment of croup?

Answer 24

Corticosteroids are beneficial due to their anti-inflammatory action. Their use decreases both laryngeal mucosal edema and the need for salvage nebulized epinephrine. Corticosteroids may be warranted even in those children who present with mild symptoms. Treatment of croup with corticosteroids has not shown significant adverse effects; however despite the low risk, their use should be carefully evaluated for children with diabetes, an underlying immunocompromised state, or those recently exposed to or diagnosed with varicella or tuberculosis, due to the potential risk of exacerbating the co-current disease process

Question 25

Is dexamethasone effective in reducing the overall severity of croup?

Answer 25

A single dose of dexamethasone has been shown to be effective in reducing the overall severity of croup, if administered within the first 4-24 hours after the onset of illness. The long half-life of dexamethasone (36-54 h) often allows for a single injection or dose to cover the usual symptom duration of croup. Studies have shown that dexamethasone dosed at 0.15 mg/kg is as effective as 0.3 mg/kg or 0.6 mg/kg (with a maximum daily dose of 10 mg) in relieving the symptoms of mild-to-moderate croup. Despite this knowledge, clinicians still tend to favor the dose of 0.6 mg/kg for initial treatment of croup. This dosage, in fact, is more effective for patients diagnosed with severe croup and remains the optimal amount for safety, benefit and cost-effectiveness.

Question 26

How is dexamethasone administered in the treatment of croup?

Answer 26

Dexamethasone has shown the same efficacy if administered intravenously, intramuscularly, or orally. [35] The route of administration is patient-dependent as based on the patient’s age, ability to tolerate orals, and severity of presenting illness. The use of inhaled corticosteroids (budesonide) with systemic treatment has not shown additional benefit.

Patients given a single oral dose of prednisolone (1 mg/kg) were found to have made more return visits, than those patients who received a single oral dose of dexamethasone (0.15 mg/kg). [37] This is due to the lesser potency to reduce inflammation and shortened half-life of prednisolone (18-36 h), when compared with dexamethasone (36-54 h).

Question 27

What is the role of epinephrine in the treatment for croup?

Answer 27

Nebulized racemic epinephrine is a 1:1 mixture of dextro (D) isomers and levo (L) isomers of epinephrine with the L form (L-epinephrine) as the active component. Its use is typically reserved for patients in the hospital setting with moderate-to-severe respiratory distress. Epinephrine works by adrenergic stimulation, which causes constriction of the precapillary arterioles, thereby decreasing capillary hydrostatic pressure. This leads to fluid resorption from the interstitium and improvement in the laryngeal mucosal edema. [23] Epinephrine’s beta2-adrenergic activity leads to bronchial smooth muscle relaxation and bronchodilation. Its effectiveness is immediate with evidence of therapeutic benefit within the first 30 minutes and then, a lasting effect from 90-120 minutes (1.5-2 h).

Question 28

How long should patients who receive nebulized racemic epinephrine for croup be observed?

Answer 28

Patients who receive nebulized racemic epinephrine in the emergency department should be observed for at least 3 hours post last treatment because of concerns for a return of bronchospasm, worsening respiratory distress, and/or persistent tachycardia. Patients can be discharged home only if they demonstrate clinical stability with good air entry, baseline consciousness, no stridor at rest and have received a dose of corticosteroids.

Question 29

Is heliox effective in the treatment of croup?

Answer 29

Heliox is a gas that contains a mixture of helium and oxygen (with not less than 20% oxygen). Delivery to the patient is via nasal cannula, face mask, or hood. It has low viscosity and low specific gravity, which allows for greater laminar airflow through the respiratory tract. Helium facilitates the movement of oxygen through the airways and decreases the mechanical work of respiratory muscles. This clinical response reduces respiratory distress. [38, 39]

Several trials of heliox have demonstrated no advantage over conventional modalities; however, other trials have shown it to be equally effective in moderate to severe croup when compared with racemic epinephrine. [40, 41, 42] Heliox has also been shown to improve symptoms in very severe croup that failed to improve with racemic epinephrine. Currently, the evidence is not sufficient to establish the beneficial effect of heliox in pediatric croup management. [43] However, heliox has been used during emergency transport of children with severe croup. Anecdotal evidence suggests that heliox does help relieve respiratory distress. [44]

Question 30

Which medications are used in the treatment of croup?

Answer 30

As previously mentioned, current treatment approaches for patients with croup are corticosteroids and nebulized epinephrine; steroids have proven beneficial in severe, moderate, and even mild croup. The anti-inflammatory action of corticosteroids reduces laryngeal mucosal edema and decreases the need for salvage nebulized epinephrine.

Question 31

Which medications are typically reserved for croup in patients with moderate to severe respiratory distress?

Answer 31

Nebulized racemic epinephrine (mixture of dextro isomers and levo isomers) or L-epinephrine is typically reserved for patients in moderate to severe distress. Epinephrine constricts the precapillary arterioles through adrenergic stimulation, thereby decreasing capillary hydrostatic pressure. This leads to fluid resorption from the interstitium and improves the laryngeal mucosal edema.

Question 32

Which medications in the drug class Corticosteroids are used in the treatment of Croup?

Answer 32

Steroids are thought to decrease airway edema via their anti-inflammatory effect. Although a subject of controversy throughout the 1980s and 1990s, corticosteroids have since become a routine part of ED management of croup. Corticosteroids have been shown to reduce hospitalization rates by 86%, and in mild disease, they have been proven to reduce the number of children returning to the ED for further treatment.

In moderate to severe disease, corticosteroids improve croup scores within 12-24 hours and decrease hospitalization rates. Most trials have used dexamethasone at 0.6 mg/kg (intramuscular or oral), but oral doses as low as 0.15 mg/kg are effective. [45] Oral and intramuscular routes appear equally beneficial. Prednisolone (1 mg/kg) has been proven effective but may be associated with a greater return of children to the ED.

Inhaled corticosteroids also have demonstrated efficacy, with most trials using budesonide. According to most authors, however, the relative ease, speed, and cost of administration make systemic corticosteroids preferable to nebulized formulations.