VIRAL CROUP

Def.: heterogeneous group of mainly acute and infectious upper airway obstruction processes that are characterized by a barking like or brassy cough and may be associated with hoarseness, inspiratory stridor, and respiratory distress.

It is acute laryngotracheitis, Laryngotracheobronchitis!

Incidence:

·       The most common form of acute upper respiratory obstruction.

·       Affect about 15% of children.

·       It is most common between 6 m΄ and 6 years of age, with a peak prevalence in the 2^nd year of life, rare over the age of 10 years.

·       Boys > girls.

·       Season; a peak in autumn and winter is associated with parainfluenza virus but can occur throughout the year.

·       Croup is uncommon < 6 months of life.

·       Rarely lasts more than 10 to 14 days.

·       Approximately 15% of patients have a strong FHx of croup.

ETIOLOGY:

·       Parainfluenza viruses type 1 , 2 and 3 (account for ≈75% of cases(

·       Other viruses including RSV, adenovirus, influenza, and measles: Influenza has been associated with more severe cases.

Pathogenesis:

·       After inhalation of the virus, the cells of the local respiratory epithelium become infected.

·       There is marked edema of the lamina propria, submucosa, and adventitia accompanied by cellular infiltration with histiocytes, lymphocytes, plasma cells, and PNLs.

·       The infant’s glottis and subglottic region are normally narrow, and a small ↓ in diameter → large ↑ in airway resistance & ↓ in airflow.

 Clinical Manifestations: "croup is a clinical diagnosis"

·       Typically, the illness starts with viral prodrome: rhinorrhea, sore throat, and low-grade fever for 1-3 days.

·       Then the child develops signs and symptoms of upper airway obstruction: characteristic barking cough, and inspiratory stridor.

·       With or without hoarse voice (Due to laryngitis).

·       Temperatures may reach 39-40°C; some children are afebrile.

·       Symptoms are typically worse at night.

·       Agitation and crying → aggravate the symptoms and signs.

·       Stridor may be present at rest or with agitation: Stridor may be inspiratory or biphasic in severe cases.

·       An increasing severity of obstruction is evident with:

 Increasing heart and respiratory rate, flaring of alar nasi, and suprasternal, intercostal, and sternal retraction.

·       As progressive hypoxia develops, the child is anxious or restless or may have depressed consciousness or cyanosis.

·       The most reliable objective measure of hypoxemia is by measuring the O2 saturation by pulse oximetry, but, in contrast to lung disease, is a late feature of upper airways obstruction.

·       On auscultation,

o   breath sounds are normal

o   No added sounds except transmission of the stridor.

o   Occasionally, there may be wheezing, indicating severe narrowing, bronchitis, or possibly coexistent asthma.

·       Physical examination should be limited to the respiratory tract and reasonable exclusion of other diagnostic possibilities.

·       Investigations should be avoided when possible.

·       Among children hospitalized for viral croup, < 1% require intubation.

·     Greater risk of severe croup: pre-existing subglottic stenosis following prolonged Mech. ventilation or Down syndrome.

·    In patients with atypical features, e.g. those aged > 6 years or with a high fever, alternative diagnoses such as epiglottitis, bacterial tracheitis, retropharyngeal abscess or inhaled FB should be considered.

·   Assessment of severity using Westley Clinical Scoring System in ED, as shown in this issue (click here).

 

Differential Diagnosis of croup:

1.     Causes of stridor (ckick here)

2.     Spasmodic croup:

o  A sudden onset of symptoms at night in a child who has been well

o  Occurs most often in children 1-3 yr of age.

o  Clinically similar to acute laryngotracheobronchitis, except that the history of a viral prodrome and fever in the patient and family are often absent.

o  last for hours rather than days.

o  Represents allergic reaction to viral antigen rather than direct infection. There is no proof of this hypothesis

o   Non- inflammatory edema of subglottic trachea

o  About 50% of cases progress to recurrent croup.

o  More of these children are boys; more have asthma, hay fever, eczema, and positive allergy prick tests; and more come from families with a history of atopy or croup than children with non-recurrent croup.

3.     Diphtheritic croup:

·       is extremely rare

·       Early symptoms of diphtheria include malaise, sore throat, anorexia, and low-grade fever.

·       Within 2-3 days, pharyngeal examination reveals the typical graywhite membrane, which can vary in size from covering a small patch on the tonsils to covering most of the soft palate. The membrane is adherent to the tissue, and forcible attempts to remove it cause bleeding.

·       Enlarged cervical lymph nodes.

·       The course is usually insidious, but respiratory obstruction can occur suddenly.

·       Culture from the membrane is essential for diagnosis.

Investigations:

·       Seldom necessary

·       Oximetry may support the clinical suspicion of hypoxia.

·       X-rays of the neck may show narrowing of the subglottic space (steeple sign) on AP or lateral views.

·       Radiographs doesn't correlate with the disease severity.

☢ Airway management should always take priority.

GENERAL PREVENTION:

Hand washing and routine personal protective equipment can help control transmission.

Management:

·       Most viral croup cases have mild airway obstruction that spontaneously resolves So → no specific treatment is indicated.

·       Cold or hot moisture should be avoided because it is distressing.

·       Supportive treatment: Iv fluid + antipyretics

·       Mild hypoxia with an oxygen saturation lower than 93% is common and closely correlated to the respiratory rate.

·       Correction of mild hypoxia is usually unnecessary.

·       Humidified Oxygen therapy is indicated When there are clinical signs of hypoxia such as : restlessness, marked tachycardia, and cyanosis

·       At the same time, treatment to relieve the obstruction is needed.

·       Admission to the PICU is indicated for children with signs of hypoxia or progressive severity of obstruction, only 1% require intubation.

·       Corticosteroids:

o   Mechanism of action: ↓ edema in the laryngeal mucosa through their anti-inflammatory action.

o   Single dose of dexamethasone 0.6 mg/kg IM or IV

o   Dexamethasone is a potent steroid with an anti-inflammatory ratio of 5:1 compared with prednisolone.

o   Prednisone or methylprednisolone: less effective.

o   Shown to ↓ emergency department length of stay, rates of admission, return visits and need for intubation in severe cases

o   Should not be given to children with varicella or TB (unless the patient is receiving appropriate antituberculosis therapy) because they worsen the clinical course.

·       Epinephrine:

o   Mechanism of action: constriction of the precapillary arterioles through the α-adrenergic receptors, causing fluid resorption from the interstitial space and a decrease in the laryngeal mucosal edema.

o   Racemic epinephrine by a dose of 0.25-0.5 mL of 2.25% racemic epinephrine in 3 mL of normal saline can be used as often as every 20 min.

o   L-epinephrine (usual dose: 0.5 ml/kg of 1 : 1,000 solution) is equally effective as racemic epinephrine and does not carry the risk of additional adverse effects.

o   Epinephrine is given via a nebulizer with a face mask and is driven with oxygen.

o   The duration of activity of racemic epinephrine is <2 hr. Consequently, observation is mandated.

o   The symptoms of croup might reappear, but racemic epinephrine does not cause rebound worsening of the obstruction.

o   Doses may be repeated every 2 hours or even more often.

o   Adverse reactions have not been reported.

o   Nebulized epinephrine should still be used cautiously in patients with tachycardia, heart conditions such as tetralogy of Fallot, or ventricular outlet obstruction because of possible side effects.

·       Heliox (helium/oxygen mixture):

o    May be equally effective but more expensive than treatment with racemic epinephrine.

o    Caution when using heliox, as it allows a greater quantity of epinephrine to be delivered to the alveoli.

·       Don't use:

o    Bronchodiltors→ ↑O2 requirement.

o    Expectroant →irritate cough receptors and cause bronchospasm

Admission Criteria:

·       Minimal or no improvement 2–4 hr after steroids given

·       Recurrence of respiratory distress during observation period

·       Persistent stridor at rest

·       Requiring multiple nebulized epinephrine treatments

·       Critical care admission criteria:

o   Severe symptoms with poor response to treatment

o   Suspected bacterial croup or tracheitis

o   Impending respiratory failure or need for mechanical ventilation

Discharge Criteria:

o  No stridor at rest o  No respiratory distress o  Normal color/perfusion or pulse oximetry

o  Have received steroids. o  normal level of consciousness o  Reliable follow-up

Discharge instructions and medications:

·       For children who present early with croup that is mild and does not warrant corticosteroid therapy, a prescription for a burst dose of steroid (prednisone 1-2mg/kg/day for 2–4 days) may be given to the parent with instructions to use if the child develops stridor at rest.

·       Return for worsening dyspnea, stridor at rest, excessive drooling, dysphagia, fatigue, or cyanosis

·       Generally, no further home medications, other than antipyretics, are indicated unless there is a comorbid condition such as:

o   Otitis media requiring antibiotics

o   Asthma exacerbation may need additional corticosteroids.

Patient Monitoring: The croup whestely score may be used to monitor response to treatment.

PROGNOSIS

·       Self-limited illness, peaking on day 2–3 of illness

·       Often recur with decreasing intensity for several days and resolve completely within 7-10 days but Cough may remain longer.

COMPLICATIONS

Complications are uncommon but may include:

·       Hypoxemia ·       Respiratory failure ·       Dehydration

·       Secondary bacterial infections: –       Otitis media –       Sinusitis –       Pneumonia –       Bacterial tracheitis