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Difficulty: HardPediatric Cardiovascular Disorders

A 3-day-old male infant is brought to the emergency department by his parents due to poor feeding, lethargy, and a bluish discoloration of his lips that started this morning. The infant was born at 39 weeks gestation via uncomplicated vaginal delivery and was discharged home at 48 hours of life. On arrival, the infant appears mottled and lethargic. Vital signs show a temperature of 36.5°C (97.7°F), heart rate of 185/min, respiratory rate of 72/min, and blood pressure of 55/35 mm Hg in the right arm and 53/34 mm Hg in the left leg. Oxygen saturation is 72% on room air. Administration of 100% oxygen via non-rebreather mask for 10 minutes raises the oxygen saturation to 74%. Physical examination reveals central cyanosis and prominent subcostal retractions. Cardiac auscultation demonstrates a single, loud second heart sound (S2) and a grade 2/6 systolic ejection murmur at the left upper sternal border. The liver edge is palpated 3 cm below the right costal margin. Femoral pulses are equal but diminished bilaterally. Capillary refill time is 4 seconds. Which of the following is the most appropriate next step in management?

  1. Initiate intravenous prostaglandin E1 infusionAnswer
  2. B
    Administer nebulized albuterol and hypertonic saline
  3. C
    Administer intravenous furosemide and obtain an electrocardiogram
  4. D
    Obtain a computed tomography angiography of the chest
  5. E
    Administer intravenous ampicillin and gentamicin

Answer

Initiate intravenous prostaglandin E1 infusion to maintain patency of the ductus arteriosus.
The correct answer is to initiate a continuous intravenous infusion of prostaglandin E1. This infant presents with severe cyanosis, tachypnea, and signs of cardiogenic shock (diminished pulses, delayed capillary refill, hepatomegaly) at 3 days of life. The failure of the hyperoxia test (minimal increase in oxygen saturation on 100% O2) strongly suggests a right-to-left intracardiac shunt rather than a primary pulmonary etiology. The single, loud S2 is characteristic of transposition of the great arteries (TGA), a cyanotic congenital heart defect that relies on a patent ductus arteriosus (PDA) or patent foramen ovale for mixing of oxygenated and deoxygenated blood. As the ductus arteriosus functionally closes around days 2-3 of life, infants with ductal-dependent lesions abruptly develop profound hypoxemia, acidosis, and shock. The most critical next step is to initiate a continuous infusion of prostaglandin E1 (alprostadil) to maintain or restore ductal patency, providing life-saving systemic oxygenation and perfusion while awaiting definitive diagnosis with echocardiography and subsequent surgical intervention.

Step-by-Step Solution

1
Interpret the clinical presentation and vital signs.
The 3-day-old infant is presenting with profound central cyanosis, tachypnea, and signs of cardiogenic shock (diminished pulses, delayed capillary refill).
Identifying shock and cyanosis narrows the differential to life-threatening neonatal conditions, primarily cardiac, pulmonary, or infectious.
2
Analyze the hyperoxia test result.
The failure of oxygen saturation to increase significantly with 100% oxygen indicates a right-to-left intracardiac shunt rather than pulmonary disease.
This differentiates cyanotic congenital heart disease from respiratory or central causes of cyanosis.
3
Correlate physical exam findings with cardiac anatomy.
A single, loud S2 and cyanosis in the first few days of life strongly suggest Transposition of the Great Arteries (TGA).
In TGA, the aorta is anterior, leading to a prominent single S2. The timing coincides with the functional closure of the ductus arteriosus, which previously allowed life-sustaining mixing of blood.
4
Determine the most critical immediate intervention.
Intravenous Prostaglandin E1 (Alprostadil) is required immediately.
Prostaglandin E1 prevents the closure of the ductus arteriosus, restoring the right-to-left shunt necessary for systemic oxygenation in ductal-dependent lesions.

Key Concept

Neonates with ductal-dependent cyanotic heart disease (like Transposition of the Great Arteries) present with severe cyanosis and shock upon ductus arteriosus closure; immediate treatment requires Prostaglandin E1 infusion.
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Topics

Pediatric Cardiovascular Disorders

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