Croup is a group of respiratory diseases that often affect infants and children under age 6. It is characterized by a barking cough; a whistling, obstructive sound (stridor) as the child breathes in; and hoarseness due to obstruction in the region of the larynx. It may be mild, moderate or severe, and severe cases, with breathing difficulty, can be fatal if not treated in a hospital.
The first step in diagnosis is to exclude other acute obstructive illnesses in the region of the larynx, such as epiglottitis, a foreign body, or angioneurotic edema of the epiglottis. Misdiagnosing an obstructive airway disease can be fatal.
The "barking" cough (often described as a "seal like bark") of croup is diagnostic. Stridor will be provoked or worsened by agitation or crying. If stridor is also heard when the child is calm, critical narrowing of the airway may be imminent.
The respiratory distress is caused by the inflammatory response to the infection, rather than by the infection itself. It usually occurs in young children as their airways are smaller and differently shaped than adults', making them more susceptible. There is some element of genetic predisposition as children in some families are more susceptible than others.
An entity known as spasmodic croup also occurs, distinct from the infectious variety, due to laryngeal spasms.
The routinely recommended treatment is with corticosteroids, although corticosteroids suppress the immune system and can predispose the child towards infection. There is a debate over how many doses to give, but Cherry in the New England Journal of Medicine recommends one dose, and has observed that children with viral, bacterial and fungal complications have had multiple doses. Epinephrine produces a significant reduction in the croup severity score but the benefit only lasts for 2 hours. Children who have moderate or severe croup with blood oxygen saturation under 92% should receive oxygen.
The treatment of croup depends on the severity of symptoms.
One of the traditional ways to treat croup is to inhale hot steam. However, studies have found that this is not effective. This was the sole treatment for croup throughout the nineteenth and most of the twentieth century. Hospitals today use a "blowby" apparatus for this purpose. Simpler remedies include taking the child outside in moist night air, or alternatively exposing the child to steam from a hot bath or a humidifier. There is little or no evidence to support their efficacy.
Mild croup with no stridor, or stridor only on agitation, and just a cough may simply be observed, or a dose of inhaled, oral, or injected steroids may be given. When steroids are given, dexamethasone is often used, due to its prolonged physiologic effects.
Moderate to severe croup may require nebulized adrenaline in addition to steroids. Oxygen may be needed if hypoxia develops. Children with moderate or severe croup are typically hospitalized for observation, usually for less than a day. Intubation is rarely needed (less than 1% of hospitalized patients).