"Croup revisited".

Of all the sounds that have the potential to wake one from a sound sleep few are so terrifying, especially to the new parent, as that of the barking cough and laborious tachypnic breathing of an infant with croup.

When we use the term "croup" we are referring to a somewhat heterogeneous catalog of disease states that affect the upper airway of the infant patient. This collection of maladies is primarily viral in nature with a few exceptions that are typified by their nature; (bacterial) and their intensity. Typically, croup involves the larynx, trachea and bronchi. When the patient is in the greatest distress it is the laryngeal involvement that is of utmost concern since laryngeal symptoms dominate the clinical presentation. The majority of croup patients are males between 3 months and five years old with the most common cases seen between the ages of 6 months to 2 years of age.

One must think of croup as a syndrome that is generally clinically diagnosed and typically manifests a set of fairly distinctive signs and symptoms. The hallmark clinical presentation is the report of a "barking" cough with inspiratory/expiratory stridor and hoarseness of the voice. This classic triad of symptoms is indicative of the anatomical reality of inflamed larynx, trachea and bronchi. The severity of the barking cough and stidor may be proportional to the degree of airway obstruction. The diagnosis of croup is a clinical diagnosis bases on the presentation of the classic symptomology and the recent patient history. Radiologic exams of the neck are of limited value. The classic "steeple" sign reported in earlier papers on croup has been seen as a normal variant in patients without croup while being absent in patients with croup. Indeed, radiologic exams can wait, as one makes the stabilization and treatment of the airway the first priority.

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Under the umbrella of "croup" are two rather distinct syndromes that follow clear clinical pathways. Spasmodic croup develops rapidly and resolves in the same fashion. Spasmodic croup is thought to be the result of an allergic cascade reaction. This accounts for the rapid onset and resolution of this type of croup. Viral croup usually follows the pattern of any viral infection with a gradual buildup that resolves just as gradually.

Laryngotracheitis is the most common cause of upper airway obstruction in the infant population. The most common cause of croup is the parainfluenza virus, which accounts for over 75% of croup cases. RSV, other influenzas and mycoplasma pneumoniae are responsible for the other 25% of cases. Of the children who experience croup, six percent will be hospitalized at a cost estimated at $67 million per year. Laryngotracheitis must be distinguished from Laryngotracheobronchitis, which is bacterial in nature and is a "super-croup" that involves the bronchial airways and their attendant anatomical structures.

Approximately 93% of all infants who exhibit croup-like symptoms can be treated and managed effectively in the patient's home. Common home remedies focus on symptom relief and comfort measures rather than attempting to reverse a pathopyhsiology. Home management requires frequent observation by the caregiver for any increase in symptom severity or discomfort. Increased work of breathing, tachypnea, stridor, retractions, worsening of the barking cough or any combination of these signs should prompt a call to the child's physician. The majority of cases do recover without a heightened morbidity at home. Humidifiers, steam, adequate hydration and rest are the most common and effective measures of home therapy.

Now we turn our attention to the 6% of croup cases that will require hospitalization and medical management. The primary objective in the treatment of croup is airway management. Perhaps the most frequently ordered therapeutic intervention for the croup patients is the administration of nebulized racemic epinephrine. Generally the medication is delivered via nebulized aerosol with 0.2 to 0.5 mls. of 1:1000 solution recemic epinephrine. This is an especially effective intervention as recemic epinephrine has been demonstrated to alleviate both mucosal edema and secretions. This drug acts within 15 to 30 minutes and has duration of 2 to 3 hours depending on the patient. This has been the mainstay treatment in the acute presentation of a child with croup and has been an indispensable element in treatment. The onset of action is rapid yet its duration is rather short producing a "rebound" of symptoms in some patients. This re-emergence of symptoms can be prevented with effective monitoring and additional treatment when needed.

The earliest treatment for croup has a rather limited clinical utility however, it remains prevalent in many clinical settings to this day. "Mist" therapy or the use of cool humidified air has been a consistent practice in the treatment of croup. Every method from boiling kettles of water to running hot showers has been utilized to produce a steady environment of humidified, "misty", air for the croup patient. Notwithstanding the anecdotal reports and tales of miraculous recoveries, there is very little evidence to support this practice. I have seen several cases where "mist" therapy has apparently produced dramatic relief of croup-like symptoms however; there have been no definitive studies that would provide an evidentiary basis for this therapy. There are those who would suggest that the cold mist may be a bronchoprovocator and should not be used at all. This claim, I would suggest, is also a position without merit as the limited research that has examined the clinical utility of this therapy has demonstrated neither harm nor therapeutic advantage. A word of caution about croup or mist tents; there is significant agreement that these devices may cause both a heightened anxiety for the patient and their families and limit the ability of the caregivers to observe and treat the patient. Their clinical efficacy is therefore questionable.

The use of an oxygen / helium mixed gas may be very helpful in patients with severe obstruction who require supplementary oxygen. The oxygen / helium mixture generally need not exceed a 30% to 70% relationship as oxygenation is rarely the problem in this patient population. Once initiated it should have an immediate and direct effect on the clinical signs of airway obstruction. If the symptoms remain as they were prior to administration of the heliox then additional symptom relief therapies should be initiated. Bear in mind, the patient needing additional oxygen therapy may require immediate airway management. Typically, croup is a disease of the upper airway and only begins to affect oxygenation when the airway becomes occluded.

The most effective and perhaps most recent of the therapeutic options for the croup patient lies in the use of glucocorticoids. The most commonly prescribed glucocorticoids are Dexamethasone and Budsonide. The glucocorticoids are extremely effective anti-inflammatory agents as they inhibit prostaglandin synthesis as well as the ability of macrophages and leukocytes to merge at inflammatory sites and they block phagocytosis and lysosomal enzyme release. The use of these agents is a mainstay of current croup management strategies. Dexamethasone is usually administered via IV while Budsonide is most commonly aerosolized.

I must emphasize that the intention of all caregivers must be to keep the croup patient relaxed and comfortable. They must feel safe, cared for and nurtured. Comfort measures will allow time to restore the croup patient to their normal respiratory status. This may include mist tents, soothing music, books and unrestricted visitation from immediate family members.

A reasonable "Best Practice" for the treatment of croup would include the following characteristics:

* Rapid identification of patients presenting with croup-like symptoms.

* Frequent clinical assessment

* Cool mist therapy via mask, tent etc.

* Racemic epinephrine

* Dexamethasone (IV or orally)

* Busonide nebulizer 

* Comfort measures

* Frequent clinical assessment

Normally croup is a syndrome that is clinically diagnosed and characteristically manifests a set of very unique signs and symptoms. It is also a syndrome we, as RCP's can impact significantly with a minimal utilization of resources and a maximum amount of caring.

by David Wheeler RRT, NPS