Croup

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. 

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. (See Etiology, Epidemiology, Prognosis, Clinical, and Treatment.)

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 (see the image below).

Child with croup. Note the steeple or pencil sign of the proximal trachea evident on this anteroposterior film. Courtesy of Dr. Kelly Marshall, CHOA at Scottish Rite.

(See Prognosis, Clinical, and Workup.)

Stridor

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.

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. (See Clinical.)

Young infants who present with stridor require a thorough evaluation to determine the etiology and, most importantly, to exclude rare life-threatening causes. Although croup is usually a mild, self-limited disease, upper airway obstruction may cause respiratory distress and pose risk of death. (See Prognosis, Clinical, and Workup.)

Patient education

For patient education information, see the Lung Disease and Respiratory Health Center, as well as Croup.

Etiology

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.

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. 

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.

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.

Spasmodic croup (laryngismus stridulus) is a noninfectious variant of the disorder, with a clinical presentation similar to that of the acute disease but typically without fever and with less coryza. This type of croup always occurs at night and has the hallmark of reoccurrence in children; hence it has also been called “recurrent croup.” In spasmodic croup, subglottic edema occurs without the inflammation typical in acute viral disease. Although viral illnesses may trigger this variant, the reaction may be of allergic etiology rather than a direct result of an infectious process.

Causes

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.

The different parainfluenza types have a more prominent role in the infectious process, as related to the patient’s age. Infection with type 3 occurs most often in infants and is the etiology of lower respiratory tract illness; by age 1 year, 50% of infants have acquired this infection. Respiratory infections in children aged 1-5 years are most often due to type 1, less so with type 2.[2]

Other infectious causes for croup-like illnesses include the following:

• Adenovirus

• Respiratory syncytial virus (RSV)

• Enterovirus

• Human bocavirus

• Coronavirus[3]

• Rhinovirus

• Echovirus

• Reovirus

• Metapneumovirus[4]

• Influenza A and B

• Rarer causes - Measles virus, herpes simplex virus, varicella

Infection with influenza A is associated with severe respiratory disease, as it has been detected in children with marked respiratory compromise. The bacterial pathogen, Mycoplasma pneumoniae, has also been identified in a few cases of croup.[5] Prior to 1970, diphtheria, also known as membranous croup, was a common cause of croup-like symptoms. Vaccine coverage for diphtheria has eliminated this infection with no case reported in the United States for decades.

Croup is the most common pediatric illness that causes acute stridor, accounting for approximately 15% of annual clinic and emergency department visits for pediatric respiratory tract infections. Croup is primarily a disease of infants and toddlers, with an age peak incidence of age 6 months to 36 months (3 years). In North America, incidence peaks in the second year of life, with an incidence of about 5-6 cases per 100 toddlers. Although uncommon after age 6 years, croup may be diagnosed in the preteen and adolescent years, and rarely in adults.

The male-to-female ratio for croup is approximately 1.4:1. The disease occurs most often in late fall and early winter, but may present at any time of the year. Approximately 5% of children will experience more than 1 episode.

Prognosis

The prognosis for croup is excellent, and recovery is almost always complete. The majority of patients can be managed successfully as outpatients, without the need for inpatient hospital care. Hospitalization rates vary widely among communities, ranging from 1.5-30% and typically averaging 2-5%. Throughout the 1990s, US hospitalizations averaged approximately 41,000 per year but appear to have subsequently decreased. Fewer than 2% of hospitalized children require intubation. Current use of steroids and nebulized epinephrine for treatment of patients with croup may thwart the need to intubate.[6] A 10-year study found a mortality rate of less than 0.5% in intubated patients, although overall exact mortality is not known.[7]

Some evidence suggests that hospitalization for croup may be associated with future development of asthma. Children hospitalized for croup have demonstrated higher levels of bronchial hyperresponsiveness and an allergic response to skin testing. Further factors that could contribute to asthma later in life are history of recurrent croup, family history of asthma, and smoking exposure in the home environment.

Complications

Complications in croup are rare. In most series, less than 5% of children who were diagnosed with croup required hospitalization and less than 2% of those who were hospitalized were intubated. Death occurred in approximately 0.5% of intubated patients.

A secondary bacterial infection may result in pneumonia or bacterial tracheitis. Bacterial tracheitis is a life-threatening infection that can arise after the onset of an acute viral respiratory infection.[8, 9, 10, 11] In this clinical scenario, the child usually has a mild to moderate illness for 2-7 days, but then develops severe symptoms. These patients typically have a toxic appearance and do not respond well to nebulized racemic epinephrine (treatment modality for croup). Cases of suspected bacterial tracheitis require hospitalization with close observation, broad-spectrum antibiotics, and, occasionally, endotracheal intubation. Key bacterial pathogens are Staphylococcus aureus including methicillin-resistant strains (MRSA), group A streptococcus (Streptococcus pyogenes), Moraxella catarrhalis, Streptococcus pneumoniae, Haemophilus influenzae, and anaerobes.

Pulmonary edema, pneumothorax, pneumomediastinum, lymphadenitis, and otitis media have also been reported in patients diagnosed with croup. Poor ability to maintain adequate oral intake, plus increased insensible fluid losses, can lead to dehydration; as such, patients may require intravenous fluid hydration to stabilize their fluid status.

Sex

Male-to-female ratio for croup is approximately 1.4:1.

Age

Primarily a disease of infants and toddlers, croup has a peak incidence in patients from age 6 months to 3 years. In North America, incidence peaks during the second year of life, at 5-6 cases per 100 children. Although uncommon after age 6 years, croup may be diagnosed in the preteen and adolescent years and, rarely in adults.[12]

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.

Spasmodic croup (recurrent croup) typically presents at night with the sudden onset of "croupy" cough and stridor. The child may have had mild upper respiratory complaints prior to this, but more often has behaved and appeared well prior to the onset of symptoms. Allergic factors may cause recurrent croup due to respiratory epithelial changes from the viral infection.

Another diagnostic consideration for patients with recurrent croup symptoms is gastroesophageal reflux (GER). Studies of children presenting with recurrent croup have reported relief of their respiratory symptoms when treated for reflux.[13]

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. 

Given the wide clinical spectrum of croup, the patient's symptoms can range from minimal inspiratory stridor to severe respiratory failure.[14] In mild cases, respiratory sounds at rest are normal; however, mild expiratory wheezing may be heard. Children with more severe cases have inspiratory and expiratory stridor at rest with visible suprasternal, intercostal, and subcostal retractions. Air entry may be poor. Lethargy and agitation occur and are due to marked respiratory difficulty and, hence, causing hypoxemia and increasing hypercarbia. Respiratory arrest may occur suddenly during an episode of severe coughing. Additional warning signs of severe respiratory disease include tachypnea, tachycardia (out of proportion to fever), and hypotonia. Children unable to maintain adequate oral intake will become dehydrated. Cyanosis is a late, ominous sign.

Scoring systems

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

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.

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

In addition, as a component of both Westley and Alberta clinical practice guidelines, recommendations for medical interventions and care are presented in an algorithm based on the severity of the patient’s initial symptoms and corresponding assessment.

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

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.

Pulse oximetry readings are within the normal reference range for most patients; however, this monitoring is helpful to assess for the need for supplemental oxygen support and to monitor for worsening respiratory compromise as evident with tachypnea and poor maintenance of oxygen saturations. Arterial blood gas (ABG) measurements are unnecessary and do not reveal hypoxia or hypercarbia, unless respiratory fatigue ensues.

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.

Procedures

Laryngoscopy is indicated only in unusual circumstances (eg, the course of illness is not typical, the child has symptoms that suggest an underlying anatomic or congenital disorder). This procedure may also be required for those patients with bacterial tracheitis to obtain the necessary cultures, in an attempt to properly tailor antibiotic treatment. Other procedures that may be indicated and require the guidance of a pediatric otolaryngologist include the following:

• Direct laryngoscopy, if the child is not in acute distress

• Fiberoptic laryngoscopy

• Bronchoscopy (for cases of recurrent croup to rule out airway disorders)[17]

A retrospective study assessed for those risk factors in children diagnosed with recurrent croup, that would predict moderate/severe findings on direct laryngoscopy and bronchoscopy and the need for further operative interventions. The authors concluded that moderate to severe findings were present in 8.7% of children with history of recurrent croup. Using statistical modeling, they reported that the two high-risk patient groups are (1) patients without a history of intubation, but with inpatient consultation and (2) patients with a history of intubation and age younger than 36 months.[18]

Radiography

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).[19]

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.[20]  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).[21] 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.[22]  Patients should be monitored during imaging, because progression toward airway obstruction may occur rapidly.

Child with croup. Note the steeple or pencil sign of the proximal trachea evident on this anteroposterior film. Courtesy of Dr. Kelly Marshall, CHOA at Scottish Rite.

Steeple sign on radiograph.

Urgent care or emergency department treatment of croup depends on the patient's degree of respiratory distress. In mild croup, a child may present with only a croupy cough and may just require parental guidance and reassurance, given alertness, baseline minimal respiratory distress, proper oxygenation, and stable fluid status. Caregivers may only need education regarding the course of the disease and supportive homecare guidelines.

Most children with mild croup symptoms can be successfully treated at home by their caregivers. Cool mist from a humidifier and/or sitting with the child in a bathroom (not in the shower) filled with steam generated by running hot water from the shower, help minimize symptoms. An adult caregiver should stay with the child during mist treatment. Engaging the child in a calming activity, such as reading a favorite book, can help decrease the child's anxiety and minimize crying, which can worsen stridor. Other suggestions for home treatment of mild croup include:

• Treat fever with an antipyretic such as acetaminophen or ibuprofen. 
• Encourage oral intake.
• Coughing can be treated with warm, clear fluids to loosen mucus in the oropharynx  
• Frozen juice popsicles also can be given to ease throat soreness
• Avoid smoking in the home; smoke can worsen a child's cough.
• Keep the child's head elevated.

  • An infant can be placed in a car seat.
  • A child may be propped up in bed with an extra pillow.
  • Pillows should not be used with infants younger than 12 months of age.
• At nighttime, parents/caregivers should stay in close proximity to the ill child so that they can immediately assist the child, if he or she begins to have difficulty breathing.

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.

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.

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.[23]  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.

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.

Cool mist administration

Historically, cool mist administration was the mainstay of treatment for croup. Hospitals had "croup rooms" filled with cool mist. Theoretically, mist moistens airway secretions, decreases their viscosity, and soothes the inflamed mucosa. Animal data show that microaerosol inhalation activates mechanoreceptors that produce a reflex slowing of respiratory flow rate and leads to improved airflow.

However, despite its continued widespread use, further evidence does not strongly support the clinical efficacy of cool mist or humidification therapy. Randomized studies of children with moderate-to-severe croup revealed no difference in outcome between those who received cool mist and those who did not.[24] However, cool mist tents are still used in the inpatient hospital setting. Besides having the potential to disperse fungus and molds if not properly cleaned, the tents separate child from parent by creating a “plastic barrier;" thus causing anxiety and agitation with potential to worsen the child’s symptoms and hinder required ongoing clinical assessment.[25, 26] In the home, cool mist humidifiers can be used; however vaporizers (heated humidification) producing hot steam to moisten the air should not be used to avoid the risk of scalding or burns.

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 for 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.[27, 28, 29, 30, 31, 32] An updated 2018 Cochrane Review reported that glucocorticoids (ie, prednisone, dexamethasone) reduced symptoms of croup at 2 hours, shortened hospital stays, and reduced the rate of return visits for patient care. This conclusive report has changed, as the previous version of Cochrane Review reported that glucocorticoids reduced symptoms of croup within 6 hours post administration.[33]

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.[34, 33]

Dexamethasone has shown the same efficacy if administered intravenously (IV), intramuscularly (IM), or orally (PO).[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.[36]

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).

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, has a lasting effect from 90-120 minutes (1.5-2 h).

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.

A study by Bagwell et al compiled information on 95,403 croup patients, ages 0 to 11 years, from the Pediatric Health Information System (2004-2014). These patients were initially evaluated and treated in various pediatric emergency departments (EDs) over this 10-year period. Their data analyses found that patients who received corticosteroids and single-dose nebulized epinephrine were managed differently from those who required multidose nebulized epinephrine. Patients who were treated with corticosteroids and multidose nebulized epinephrine, and subsequently discharged from the ED, were less likely to return for further care; however, if discharge from the ED did not occur, these patients were hospital-admitted at a higher rate when compared to patients receiving a single-dose nebulized epinephrine treatment in the ED setting.[38]

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.[39, 40]

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.[41, 42, 43] Heliox has also been shown to improve symptoms in very severe croup that failed to improve with nebulized racemic epinephrine. Currently, the evidence is not sufficient to establish the beneficial effect of heliox in pediatric croup management.[44]  However, heliox has been used during emergency transport of children with severe croup. Anecdotal evidence suggests that heliox does help relieve respiratory distress.[45]

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 cases of croup. The anti-inflammatory action of corticosteroids reduces laryngeal mucosal edema and decreases the need for salvage nebulized epinephrine. 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.[46]

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. Because of the potential adverse effects of tachycardia and hypertension, it is reserved for children with moderate to severe disease.[23]

Class Summary

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. 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.

Dexamethasone (Baycadron)

Several studies have shown improvement in clinical symptoms and croup score in hospitalized and ED patients who received dexamethasone. The drug exerts a beneficial effect via anti-inflammatory action that decreases laryngeal mucosal edema. The onset of action occurs within 6 hours after oral or intramuscular administration. Dexamethasone has a long pharmacodynamic effect of 36-56 hours. No studies have evaluated the effect of multiple doses of the drug.

Prednisone

Several studies have shown improvement in clinical symptoms and croup score in patients who were treated while hospitalized or in the ED. Corticosteroids exert beneficial effect via anti-inflammatory action in which laryngeal mucosal edema is decreased. In calculating an appropriate prednisone dose, it is important to know that dexamethasone is 6.67 times more potent and has a long half-life of 36-56 hours, versus a median half-life of 18-36 hours for prednisone.

Prednisolone (Prelone, Pediapred, Millipred)

Corticosteroids exert beneficial effect via anti-inflammatory action in which laryngeal mucosal edema is decreased. Like with prednisone, in calculating an appropriate prednisolone dose, it is important to know that dexamethasone is 6.67 times more potent and has a long half-life of 36-56 hours, versus a median half-life of 18-36 hours for prednisolone.

Budesonide inhaled (Pulmicort Respules, Pulmicort Flexhaler)

Clinical studies have documented improvement in symptoms and decrease in hospital admissions with nebulized budesonide in children with croup. Inhaled budesonide has been shown in several studies to be equivalent to oral dexamethasone.

Corticosteroids exert beneficial effect via anti-inflammatory action in which laryngeal mucosal edema is decreased.

Class Summary

Epinephrine stimulates alpha receptors and beta2 receptors. It constricts the precapillary arterioles, thus decreasing airway edema. Because of the potential adverse effects of tachycardia and hypertension, it is reserved for children with moderate to severe disease.

The effects of epinephrine are transient, and most trials show alleviation of symptoms for no longer than 2 hours. In the 1980s and early 1990s, a rebound phenomenon was thought to occur, necessitating admission of all children who received the drug. However, patient discharge after 3-4 hours of observation has since become acceptable, as long as the patient has no stridor at rest, normal air entry, normal color, and normal consciousness and has received a dose of steroids.

Epinephrine (Adrenalin)

This agent is a levo isomer. It stimulates alpha-, beta1-, and beta2-adrenergic receptors, which results in bronchodilatation, increased peripheral vascular resistance, hypertension, increased chronotropic cardiac activity, and positive inotropic effects. Epinephrine causes alpha-adrenergic receptor–mediated vasoconstriction of edematous tissues, thus reversing upper airway edema.