CROUP
DEFINITION:
An acute viral syndrome of the larynx characterized by sub-glottic
stenosis leading to cough, inspiratory stridor, hoarseness, and
respiratory distress.
EPIDEMIOLOGY:
- incidence: ?
- age of onset:
- primarily a disease of children 6 months -> 6 years
- usually < 3 years with peak in 2nd year and mean at 18
months
- unusual after school age reached
- risk factors:
- M > F (1.4:1)
- season - late fall to early winter with peak in November
- strong family history with tendency to recur
PATHOGENESIS:
- Parainfluenzae virus type 1 (48%), 2 (18%), 3 (8.6%) and
causes croup in all age groups
2. Minor (20.5%)
- 10% - RSV (< 5 years)
- 3.6% - Influenzae virus type A (> 5 years)
- 3.6% - Mycoplasma pneumoniae "
- 3.3% - Influenzae virus type B "
3. Rare (5.3%)
- adenovirus, enterovirus, measles, mumps, rhinovirus
- corynebacterium diphtheriae
2. Pathogenesis
- viral invasion of the laryngeal mucosa leads to
inflammation, hyperemia, edema, epithelial necrosis, and
shedding of this region which leads to irritation (cough),
reactive paralysis of the vocal cords (hoarseness), airway
obstruction of the fixed subglottic region (continuous stridor)
and/or collapsable supraglottic region (inspiratory stridor),
and respiratory distress
CLINICAL FEATURES:
- croup usually preceded by an upper respiratory tract
infection
2. Signs/Symptoms
- Cough
- spasmodic and barking (seal-like)
- usually worse at night and waxes and wanes
- Hoarseness
- Inspiratory Stridor
- with inspiratory retractions and tachypnea
- prolonged inspiratory stridor
- Respiratory Distress
- Others
- expiratory wheezes (when bronchi & bronchioles involved)
- decreased breath sounds with atelectasis
- transmitted upper airway sounds
- fever in 83% of children (usually < 39 C)
- acute stage lasts 3-4 days
- rhinitis, conjunctivitis
3. Complications
- pneumonia (9%)
- obstructive bronchitis (7%)
- respiratory failure with intubation, death (<2.7%)
- most common cause of airway obstruction in children 6 months
-> 6 years.
- hospitalization occurs in 1.5-15% of cases
- not usually associated with sepsis
DIAGNOSIS:
- rule out epiglottitis and foreign body aspiration
- clinical
- radiologic
- direct visualization in the OR
INVESTIGATIONS:
- leukocytosis (>15 in 20% of patients)
- elevated PMN and lymphocytes
2. Blood Gas
2. Imaging Studies
- "Steeple" Sign
- seen on AP view and appears in 40-50% of cases
- indicates subglottic narrowing (pencil-thin)
- smooth tapering of the subglottic airway
- widening of the hypopharynx on lateral view
2. Chest X-Ray
- hyperinflation
- atelectasis
3. Virology
- specimens obtained from oropharynx
- isolation rate: 38%
MANAGEMENT:
- dependent upon the degree of severity:
- noisy breathing with no distress
- send home if parents good and close distance
- instructions (see sheet):
- sleep in propped up position
- humidifier by bedside
- encourage fluids
2. Moderate
- moderate respiratory distress not responsive to therapy
- complications, i.e., poor feeding, dehydration
- admit to hospital with:
- humidified air in croupette
- humidified oxygen if PaO2 < 60 mmHg
- dexamethasone
- racemic epinephrine (2.25%)
3. Severe
- risk of airway obstruction
- treat like epiglottitis
- used since late 19th century - "croup kettles"
- proposed mechanisms of action:
- moistens secretions -> easier to cough up
- soothes inflammed laryngeal mucosa -> decrease cough
- has no effect on subglottic edema or total respiratory
resistence
- humidified oxygen
- no evidence of benefit in treating hypoxia possibly due
to impaired diffusion capacity, V/Q mismatch, and/or
pulmonary edema
2. Racemic Epinephrine
- used since 1971
- proposed mechanism of action
- alpha-adrenergic stimulation causes mucosal
vasocon-striction leading to decreased edema in the
inflammed subglottic region -> decreased airway obstruction
- effect
- transient improvement 10-30 minutes after administration
but the degree of obstruction returns to baseline or above
by 2-4 hours after administration (rebound)
- dose
- nebulized 0.25 cc of 2.25% racemic epinephrine in 2 cc
NS q2-4h prn (may have to use until steroid starts to work)
3. Dexamethasone
- used since the early 1960's
- proposed mechanism of action
- decreases subglottic edema by suppressing local
inflamma-tion, shrinking lymphoid swelling, and/or
decreasing capillary permeability
- effect
- decreases length and severity of respiratory symptoms
and length of hospital stay; works within 12-24 hrs
- routes
- 0.8 mg/kg/dose decadron po bid x 4
- 0.6 mg/kg dexamethasone phosphate IM upon admission
- 0.25-0.5 mg/kg/dose dexamethasone IV q6h
Parent's Instruction for a Child With Croup*
When your child has croup, they have a virus that causes swelling
of the voice box and other parts of the airway. The swelling causes
that harsh, barking cough. There is no specific medication for croup
because it is a virus. However, there are some steps you can take at
home to help your child's breathing and help him or her rest.
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