A 2-month- - pacemaker

[ArchivalUser]

A 2-month-old male infant is brought to the emergency
department with wheezing and rapid breathing for the
last 2 days. He was born at full term with a birth weight
of 7 lb, 2 oz, and was well until 2 days ago when he developed
a fever of 38.8 C (101.8 F) and runny nose. He
began to cough and then became œwheezy. He has been
irritable and unable to feed from the bottle without
pausing several times, and has vomited twice. There is a
4-year-old elder brother who has had a runny nose for
the past week.Vital signs are: pulse 146/min, respirations
56/min, blood pressure 84/58 mm Hg, temperature 37.3
C (99.1 F), and oxygen saturation (by pulse oximetry)
96% on room air. Examination shows an active and alert
baby in mild respiratory distress. The nose is blocked
with clear secretions, while the throat and ear examination
is normal. He has slightly reduced breath sounds on
both sides and bilateral rhonchi. Cardiac examination is
normal and there is no hepatosplenomegaly. Which of
the following studies is most likely to reveal the etiology
of the illness?
(A) Bronchoscopy
(B) Chest x-ray
© Complete blood count
(D) Nasopharyngeal aspirate
(E) Throat swab

[ArchivalUser]

dd

[ArchivalUser]

(D) Nasopharyngeal aspirate

[ArchivalUser]

The correct answer is D. Bronchiolitis is one of the
most common respiratory illnesses in infants during
the winter season. It is most commonly due to respiratory
syncytial virus (RSV), which causes inflammation
of the small airways, causing obstruction and trapping
of air. Clinically, this manifests as coughing, wheezing,
and hyperinflated lung fields on chest x-ray. Often there
is a mild fever and a prominent rhinitis, which can
increase the breathing difficulty by causing nasal blockage.
The diagnosis, based upon demonstration of RSV
antigen in the nasopharyngeal aspirate, is both rapid
and specific.
Bronchoscopy (choice A) is very important when foreign-
body aspiration is suspected. Toddlers form the
highest risk group for aspiration of foreign body, which
is uncommon in very young infants.
Chest x-ray (choice B) will show hyperinflation of lung
fields or sometimes interstitial infiltrates in infants with
bronchiolitis. The changes are not specific for RSV
infection.
Complete blood count (choice C) is helpful for diagnosis
of bacterial pneumonia (leukocytosis with increased neutrophils)
and pertussis (lymphocytosis). It is generally not
helpful in diagnosing RSV infection.
Throat swab (choice E) is used when acute pharyngitis
is suspected. This is usually a problem in older children
who present with sore throat and tonsillar enlargement
with exudates. Rapid diagnosis of streptococcal infection
is possible on throat swabs obtained at the office.