W. Steven Pray, PhD, DPh

Disclosures

US Pharmacist. 2006;31(7) 

Croup causes substantial morbidity, especially during flu seasons. The characteristic barking cough it produces can be extremely troubling to parents, as they often think their child is seriously ill. Fortunately, most cases of croup are mild and are treatable with simple self-care measures such as vapor therapy.

Croup is a community-acquired infection that results in inflammation of the larynx, bronchi, and trachea. In children, it is usually sufficiently mild for outpatient treatment, but the less common form seen in adults may require hospitalization.[1,2] Croup occurs in as many as 6% of children ages 6 months to 6 years.[3]

Etiology

Croup may be due to such bacteria as Mycoplasma pneumoniae, Corynebacterium diphtheriae, or Streptococcus pneumoniae.[1] However, viral invaders are most often responsible for pediatric croup, also known as laryngotracheobronchitis.[4] Parainfluenza causes more than 66% of cases, and the particular variant caused by human parainfluenza virus 1 has the peculiar phenomenon of occurring since 1973 in odd-numbered years.[1,2,4,5] Clinicians also observe a clustering of croup cases corresponding to outbreaks of influenza A and B.[1,4,5] Croup resulting from influenza A is less common but more severe than croup arising from parainfluenza or respiratory syncytial virus.[5] Other viruses that may cause croup include metapneumovirus, adenovirus, rhinovirus, enterovirus, measles virus, and herpes simplex virus.[4] Patients usually contract these viruses via the standard mechanisms by which aerosolized viral illnesses are contracted (e.g., direct inhalation, contamination of the hands followed by touching the mucosa of the eyes, nose, or mouth).[1] The incubation period is two to six days.[4] Following inoculation, the progression of the viral invaders is to the nasal mucosa and trachea. Airways are narrowed by inflammation of the larynx, trachea, and bronchi, as well as by heightened production of mucus.

Epidemiology

Croup is most common in children ages 6 months to 3 years, although it can be seen up to age 15 years and occasionally in adults.[1,4,6,7] Viral croup is more common in males, with a male–female ratio of 3:2.[4,6] The peak age for viral croup is 2 years.[2] Most cases arise in the winter or fall.[6] If one member of a family has croup, the risk of passing it to other members of the household is 15%.[6]

Manifestations of Croup

Patients undergo a prodrome of two- to four-day duration in which they perceive the onset of a respiratory infection in the upper airways, manifested by rhinorrhea, mild cough, and low-grade fever.[4] Eventually, release of inflammatory factors causes erythema, exudate, and inflammation, culminating in symptoms such as cough. The cough of croup is a harsh barking, resembling the sound made by a seal.[1,8] The cough may produce hoarseness from swelling of the vocal cords.[4,9] Swallowing is usually unaffected. Croup often worsens at night, leading to many visits to emergency departments and late-night calls to family physicians.[8]

Croup is the most common cause of nonchronic pediatric stridor.[6] Stridor on inspiration coexisting with coarse rhonchi is caused by a turbulent airflow arising from respiratory obstruction.[10] The patient may suffer shortness of breath, tachycardia, or tachypnea.[7] Nostrils may flare. Babies and young children may exhibit supraclavicular, infraclavicular, intercostal, and sternal retractions, where the chest and stomach muscles appear to suck in with each breath.[4,8] Rhinorrhea may also be present, but fever is absent or mild. The child may be unable to rest normally.[7] The lips and fingernails may demonstrate the classic signs of anoxia as they begin to show a blue tint.[7]

Medical examination of patients with croup reveals a narrowing of the subglottic area with edema, resulting in a radiologically identifiable abnormality known as the "steeple sign."[1] The child's airway is at its most narrow in the subglottic area. For this reason, any inflammation or narrowing in this location is highly likely to cause airway compromise.[6]

Croup seldom causes serious sequelae.[7] Only about 1.3% to 2.6% of patients require hospitalization.[4,9] The duration of croup is typically three to five days.[7] A mild cough may persist for several days after the most serious symptoms have regressed. There is an association between a history of croup and asthma, but it is unclear which is causal for the other. In one study, a recent diagnosis of croup (within one year of the survey) almost doubled the risk for asthma.[11]

Treatment of Croup

Many patients with croup have mild cases that can be treated at home, but there are exceptions.[7] Patients should be urged to see a physician if the child's lips and fingernails are blue, if there is evident trouble breathing, if drooling or trouble swallowing is present, if the child is restless or confused, or if vapor therapy does not result in improvement.[7] Patients with cyanosis, extreme pallor, agitation, or decreased awareness of their surroundings, or those who are becoming fatigued from the effort of breathing, should be given supplemental oxygen immediately.[10]

Croup of bacterial origin requires appropriate antibiotic therapy. If the patient has stridor at rest, physicians often admit the patient to the hospital until the stridor has halted.[12] Steroid therapy is usually effective in reversing the stridor, perhaps as soon as six hours after therapy is begun.[12,13] Inhaled steroids are often used.[9] Oral prednisolone in a dose of 1 mg/kg is often effective.[12] In a randomized trial, investigators discovered that a single dose of dexamethasone (0.6 mg/kg) was effective in speeding resolution of mild croup in children.[14] A Cochrane analysis revealed that steroids reduce symptoms and readmissions to emergency departments, shorten hospital stays, and reduce the need for treatment with epinephrine.[3]

Most children with croup have a mild case, and they appear to be normal in observable behaviors such as hunger and thirst, they engage in play activities, and they display their usual disposition.[10] Standard treatment for most mild cases of croup is inhaled vapor therapy to ensure that airway secretions retain adequate hydration.[5] One physician suggests that parents/caregivers take the child into a steamy bathroom, as the moisture will improve the condition.[8] While conceding that the suggestion may not be fully reference based, the physician asserts that steam "carries the weight of decades of practice." Another suggestion is to place a clean, wet washcloth over the nose and mouth, so each breath becomes humidified.[7]

Patients are often advised by physicians to humidify the child's bedroom with a vaporizer or humidifier. Pharmacies usually stock an array of humidification devices, ensuring that patients can obtain a product that meets their needs.

Steam vaporizers are available in several configurations. Electrode vaporizers require filling a reservoir to the indicated point, followed by placement of a boiling chamber into the reservoir. Steel or carbon electrodes within the boiling chamber are immersed in the water when the boiling chamber is placed into the reservoir. When the outlet is connected to electricity, elements normally found in water (e.g., calcium, magnesium, iron) serve to conduct the electricity between the electrodes, heating the water. After a short period, the heated water exits the vaporizer outlet as sterile steam. If the water is excessively soft, the patient should add electrolyte to the water. Some companies advise salt, while others advise baking soda. The purchaser should be encouraged to read the product brochure in order to determine the recommended electrolyte and the suggested amount to add. On the other hand, if the water already contains excessive electrolyte, some vaporizers eject boiling water from the steam outlet. In these cases, the consumer should be advised to dilute household water with distilled water until boiling water is no longer ejected.

Other vaporizers function by heating the water with a heating element. The amount of electrolyte is not an issue in steam generation, since the heating element is not dependent on it.

Both types of vaporizers produce heated mist that can alleviate croup. Because steam has the potential to burn, all vaporizers should be placed at least 4 feet from patients. They should also be placed away from household traffic flow, such as in a corner away from doors. The patient may choose to use medication with a vaporizer. Several brands are available, containing volatile oils that have been proven safe and effective for cough through the FDA review process.

Patients may choose cool-mist humidifiers to humidify their child's room. The traditional type has a reservoir into which a rapidly rotating spindle is immersed. As the spindle rotates, water in the reservoir is drawn upward onto a spinning disk, which breaks it down into small droplets. The fan action of the disk disperses the water into the room. Patients may also purchase ultrasonic humidifiers--devices that use ultrasonic technology to create an ultrafine mist. Distilled water is optimal for both types of humidifiers, as electrolyte in the water droplets can produce an annoying white dust of calcium and other electrolytes on surfaces. The white dust can interfere with electronic equipment (e.g., computers, VCRs) if the humidifier is allowed to run too close to them.

Croup is worsened by agitation or crying.[4] Thus, parents should be urged to make the child as comfortable as possible under the circumstances.

Prevention of Croup

As croup is a transmissible respiratory disease, prevention steps are those usually employed in the prevention of similar conditions, like the common cold and influenza.[7] People should wash their hands often, keeping fingers away from the nose and mouth. Any potentially infected facial tissues should be handled as infectious materials and should be discarded immediately and not handled by others. Toys or other objects that have been mouthed by a child with croup should be washed to eliminate pathogens. Visitors or relatives with cough should avoid holding or playing with children in the home.

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