A 1-hour-old male neonate is evaluated in the neonatal intensive care unit for respiratory… — USMLE Step 2 CK

A $1$ -hour-old male neonate is evaluated in the neonatal intensive care unit for respiratory distress. He was delivered at $37$ weeks gestation via an elective, scheduled cesarean delivery to a $28$ -year-old gravida 2, para 2 mother. The mother's pregnancy was uncomplicated, and there is no history of prolonged rupture of membranes, maternal fever, or meconium-stained amniotic fluid. Birth weight is $3100\text{ g}$ . Apgar scores were $7$ and $8$ at $1$ and $5$ minutes, respectively. Vital signs are temperature $37.0^\circ\text{C}$ ( $98.6^\circ\text{F}$ ), heart rate $155/\text{min}$ , and respiratory rate $72/\text{min}$ . Physical examination reveals an infant with mild intercostal retractions, nasal flaring, and grunting. Breath sounds are clear and equal bilaterally with no murmurs.

An arterial blood gas on room air reveals the following:

Measurement	Value	Reference Range
$pH$	$7.32$	$7.35 - 7.45$
$pCO_2$	$50\text{ mm Hg}$	$35 - 45\text{ mm Hg}$
$pO_2$	$60\text{ mm Hg}$	$50 - 80\text{ mm Hg}$
$HCO_3^-$	$24\text{ mEq/L}$	$22 - 28\text{ mEq/L}$

A chest radiograph demonstrates lung hyperinflation, prominent perihilar vascular markings, and fluid within the interlobar fissures. Which of the following is the most appropriate next step in the management of this patient?

Provide supportive care with oxygen supplementation or continuous positive airway pressureAnswer
B
Administer nebulized albuterol and oral dexamethasone
C
Obtain blood cultures and initiate intravenous vancomycin and cefepime therapy
D
Insert an orogastric tube and prepare for an emergent exploratory laparotomy
E
Administer the live-attenuated intranasal influenza vaccine

Answer

Provide supportive care with oxygen supplementation or continuous positive airway pressure

The neonate presents with classic signs of transient tachypnea of the newborn (TTN), characterized by early-onset respiratory distress in a term or late-preterm infant, especially following a cesarean delivery without labor. The pathophysiology involves delayed resorption and clearance of fetal alveolar fluid. The chest radiograph findings of hyperinflation, prominent perihilar streaking, and fluid in the interlobar fissures are pathognomonic. TTN is a self-limiting condition, and the most appropriate next step is supportive care, which includes providing supplemental oxygen or continuous positive airway pressure (CPAP) to maintain adequate oxygenation while the fluid is naturally resorbed over 24 to 72 hours.

Step-by-Step Solution

Analyze the patient's gestational age, delivery method, and risk factors.

The patient is a 37-week (term) neonate born via scheduled cesarean delivery without labor, with no infectious risk factors.

Scheduled cesarean sections bypass the physiological stress of labor, leading to decreased catecholamine release, which normally triggers the resorption of fetal lung fluid.

Interpret the physical examination and laboratory findings.

The infant exhibits tachypnea and increased work of breathing within the first hour of life, accompanied by mild respiratory acidosis on the arterial blood gas.

These signs indicate acute respiratory distress, necessitating rapid identification of the underlying etiology to guide appropriate management.

Correlate the clinical presentation with the radiographic findings to establish a diagnosis.

The chest radiograph shows hyperinflation, perihilar vascular prominence, and fluid in the interlobar fissures, strongly indicating Transient Tachypnea of the Newborn (TTN).

These radiographic hallmarks distinguish TTN from other causes like Respiratory Distress Syndrome (which shows low lung volumes and a ground-glass appearance) or Meconium Aspiration Syndrome (patchy infiltrates).

Determine the most appropriate evidence-based management for the diagnosed condition.

Supportive care with supplemental oxygen or continuous positive airway pressure (CPAP) is indicated.

TTN is a benign, self-limiting condition that resolves as the lymphatic system slowly clears the retained fetal lung fluid over 1 to 3 days.

Key Concept

Transient tachypnea of the newborn (TTN) typically presents in term or late-preterm infants delivered via cesarean section without labor. It manifests as early respiratory distress with radiographic findings of retained lung fluid and is managed with supportive care.

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