Croup is a common disorder in infants and young children, in which narrowing and inflammation of the airways causes hoarseness, stridor (a grunting noise during breathing), and a barking cough.
Croup may be caused by a viral or bacterial infection affecting the larynx, epiglottis, or trachea. Most cases are due to a viral infection and are generally mild.
Other causes include diphtheria, allergy, spasm due to insufficient calcium levels in the blood, and inhalation of a foreign body. Humidifying the air can help to ease breathing. In some cases, cortico-steroid drugs administered through a nebulizer, and oxygen, may be prescribed. If the infection is bacterial, it is treated with antibiotic drugs.
Croup in detail - technical
Croup is a common childhood problem with a peak incidence of 60 per 1000 child years in those aged between 1 and 2 years. All children who present to emergency departments with croup should be treated with steroids, oral dexamethasone 0.15mg per kg or prednisolone 1mg per kg being the drugs of choice.
A compromised but functioning airway should never be made worse by upsetting the child. Children who require epinephrine (adrenaline) may be sent home safely provided they have also received steroids and have improved sufficiently to have no stridor at rest over a number of hours.
The term croup describes an acute clinical syndrome of hoarse voice, barking cough, and stridor; it is usually seen in young children. Croup results from swelling of the upper airway, in and around the larynx, usually as a result of a viral infection.
Parainfluenza virus type 1 accounts for around half the cases during winter, and parainfluenza type 2, influenza type A, adenoviruses, respiratory syncytial virus, enteroviruses, and possibly mycoplasma pneumonia cause most of the other cases. Croup is a common childhood problem with a peak incidence of 60 per 1000 child years in those aged between 1 and 2 years, although it may be seen up to the teenage years. As such, it is by far the most common cause of acute upper airways obstruction likely to present to emergency departments.
Unless otherwise qualified, the term ‘croup’ in this article refers to viral laryngotracheobronchitis. In viral laryngotracheobronchitis the causative virus is transmitted via the respiratory route with the port of entry being the nose and nasopharynx. Viral replication occurs, and as the infection spreads, the walls of the larynx and trachea become edematous with a fibrinous exudate partially occluding the lumen of the trachea. In addition to luminal narrowing, edema of the vocal cords and subglottic larynx leads to stridor, hoarseness, and a characteristic bark-like cough.
Distress caused by obstruction tends to be most marked in younger children due to the small size of their larynx, the presence of loose submucous tissues, and the tight encirclement of the subglottic area by the cricoid cartilage. This is the narrowest airway point in children under 8 years of age. Any swelling in this area due to inflammation results in significant impingement on the airway. The younger the child is, the greater the need to monitor them closely.
The typical presentation of croup is in a preschool child with a history of a recently acquired upper respiratory tract infection. The child develops a barking or seal-like cough, a hoarse voice, and, if obstruction is severe enough, stridor. If stridor is inspiratory this indicates obstruction at the laryngeal level or above while expiratory stridor or biphasic stridor indicates problems in and around the trachea and more severe obstruction. Less commonly, older children may present with recurrent croup with no viral prodrome. They and their families tend to be atopic and suffer from asthma more than the general population. They should, however, be treated in the same manner as those with ‘viral’ croup. In the smaller child especially, problems with feeding, swallowing difficulties, and whether the child has been cyanosed should be ascertained.
It is important to know whether or not the child has had croup in the past and specifically whether the child has had mild stridor in between acute attacks. This is important as any child who has a pre-existing narrowing of the airway is much more likely to proceed to dangerous obstruction with an acute obstruction superimposed on it. Immunization history is important to obtain to exclude the diagnosis of diphtheria, which is very rare, and to check whether the child has been given the Hib vaccine should epiglottitis be suspected.
Most children with croup are not distressed and have only a barking cough with no stridor at rest or stridor that is audible only with physical activity. Signs due to viral illness such as mild fever and nasal discharge are often present. In more severe cases, the child may have a more pronounced stridor at rest. If obstruction progresses, the child may exhibit increasing substernal, intercostal, and subcostal retractions. A worrying sign is that of altered consciousness reflected as anxiety, restlessness, and obvious fatigue. Decreased air entry and respiratory effort, extreme pallor, and cyanosis require immediate intervention. Patients with mild croup should have their throats examined but this should be deferred in more severe cases. A compromised but functioning airway should never be made worse or compromised by upsetting the child.
The child’s preferred position may also give clues as to the severity of obstruction and to a diagnosis other than croup. Hyperextension or other abnormal positioning of the neck may suggest epiglottitis or a retropharyngeal abscess.
Oximetry is of limited value as children may maintain oxygen saturations in the high nineties even when badly obstructed. In difficult diagnostic cases, a lateral soft tissue X-ray of the neck may help; however, the possible benefits should be weighed against the risks of moving or disturbing the child if obstruction is more than mild and expert advice should be sought. Croup, however, is usually an easy ‘spot diagnosis’ requiring no diagnostic tests.
Although rare, it is important to establish that other more sinister causes of acute upper respiratory tract obstruction masquerading as croup are not present. Especially in the younger child one should inquire regarding long-term symptoms preceding the present episode, such as low-grade stridor. This might suggest underlying congenital airway or a vascular anomaly (e.g., tracheomalacia, congenital subglottic stenosis, congenital bilateral cord paralysis, laryngeal web, or vascular ring compression of the trachea). One should also inquire as to possible trauma, toxic ingestions, dysphagia, and drooling.
Drooling may suggest epiglottitis, peritonsil abscess, or foreign body in the airway or esophagus. Classic croup and epiglottitis are hard to confuse as the latter usually presents as a pale, toxic, drooling child with a short history who does not cough much. Early on, however, the distinction may be more difficult to make. A child with severe croup with a high fever who does not respond to epinephrine and steroids may have tracheitis and will need a more aggressive approach.
The possibility of a foreign body should be kept in mind for children who do not respond to treatment or have a prolonged course. While usually parents will volunteer a history of an acute obstruction or a sudden coughing fit the history may not always be known to them. A definitive diagnosis may be made by directly viewing the upper airway but this should only be done by an experienced pediatric anaesthesiologist, intensivist, or emergency physician in an appropriate clinical setting.
Treatment and Disposition
All children who present to emergency departments with croup should be treated with steroids. Prior to the regular use of steroids a general rule of thumb was to admit children with stridor at rest to hospital for observation while allowing those with occasional stridor and barking cough only to be managed at home. As many children will improve within a few hours of taking steroids they may be discharged home after a short stay in an emergency department or an observation ward.
Other factors such as the distance of home from medical care, the availability of transport, the child’s past history with regard to severe airway obstruction, and parental concern and attitude all need to be taken into account when making the decision to admit. Oral dexamethasone in a one-off dose of 0.15mg per kg (or an equivalent dose of prednisolone of 0.75mg per kg) is recommended. Most children with croup will require only one dose but if croup (as opposed to viral) symptoms persist, a further dose may be given 24 h later. It is often more convenient to use prednisolone (rounded off to a simple 1mg per kg) in the community as it is more readily available. Unpublished work suggests that children treated with prednisolone may present more commonly than those treated with dexamethasone and would benefit from a second dose. Steroids may be administered intramuscularly or intravenously (in injectable form) in the rare case of severe obstruction where there is concern that the child may aspirate given their respiratory difficulties.
Oral dexamethasone has been found to be as effective as inhaled steroids such as budesonide and to work as fast at a fraction of the cost. Combining dexamethasone and budesonide is no more effective than dexamethasone alone. There is no place for antibiotics in a typical case of croup. The effectiveness of ‘steam’ or humidified air is largely unproven despite its once common usage.
Where obstruction is judged to be severe, the use of nebulized epinephrine should be considered. It is generally considered that epinephrine does not change the natural history of croup, such as length of stay in hospital or need to intubate, due to its short-lasting effects. However, it will buy time while waiting for steroids to take effect or waiting for an anaesthesiologist to arrive in a worst case scenario. Five milliliters of 1 in a 1000 epinephrine (adrenaline) nebulized with oxygen can be used for all children and may be repeated after 10 min if needed. While in the past it was recommended that any child who received epinephrine for croup should be admitted, a number of studies have now shown that children may be sent home safely provided they have also received steroids and have improved sufficiently to have no stridor at rest over a number of hours.
The universal use of steroids for croup in emergency departments has resulted in a fall in the relapse rate of those sent home, a fall in the average length of stay in hospital, and a dramatic reduction in the number of children needing intensive care and intubation.
Most children with croup have mild symptoms and do not need hospitalization, and will recover within a few days. Their symptoms will be shortened even further with the use of steroids. Despite the substantial impact of steroids an occasional child will still follow a prolonged course with cough and marked stridor for many days. While other diagnoses such as foreign body need to be considered, most children will settle with time.
For most children, croup is a one-off episode and well tolerated especially if steroids are used. Children who suffer repeated episodes of recurrent croup as described above may benefit from steroid use at home at the first hint of croup symptoms. Although no trials have evaluated this approach, anecdotal evidence suggests this practice appears to have benefit.
Although once controversial, use of steroids is now generally accepted for all children who present to emergency departments with croup. While it is clear that both prednisolone and dexamethasone are effective in the treatment of croup, direct comparisons have not been published as yet. Unpublished work suggests the shorter half-life of prednisolone may result in a greater number of children returning to medical care. While a once-only dose of dexamethasone is sufficient for the vast majority of children with croup, a second dose of prednisolone 24 h later may be needed in some cases.
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