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Difficulty: MediumPediatric Cardiovascular Disorders

A 10-month-old boy is brought to the emergency department by his parents following an episode of profound cyanosis. The parents report that he was crying inconsolably when he suddenly developed blue discoloration around his lips and began breathing very rapidly. His mother states she instinctively brought his knees to his chest, which seemed to gradually improve his color over several minutes. The patient has a history of a heart murmur, but the family recently immigrated and his medical records are unavailable. He is currently resting quietly. Vital signs are temperature 37.1°C (98.8°F), heart rate 130/min, respiratory rate 28/min, and blood pressure 85/50 mm Hg. Oxygen saturation is 94% on room air. Cardiac auscultation reveals a normal S1, a single S2, and a grade 3/6 harsh systolic ejection murmur heard best at the left upper sternal border. If a similar cyanotic episode recurs while the patient is in the emergency department, which of the following is the most appropriate next step in management?

  1. Administration of supplemental oxygen and intravenous morphineAnswer
  2. B
    Initiation of nebulized albuterol and oral corticosteroids
  3. C
    Administration of intravenous furosemide and digoxin
  4. D
    Procurement of an arterial blood gas to calculate expected respiratory compensation
  5. E
    Infusion of broad-spectrum intravenous antibiotics

Answer

The correct intervention is the administration of supplemental oxygen and intravenous morphine.
Tetralogy of Fallot is the most common cyanotic congenital heart disease, characterized by an overriding aorta, ventricular septal defect (VSD), right ventricular hypertrophy, and right ventricular outflow tract (RVOT) obstruction. Patients frequently experience hypercyanotic 'Tet' spells, which are triggered by events that decrease systemic vascular resistance (SVR) or increase sympathetic tone (e.g., crying, feeding). This leads to infundibular spasm, acutely worsening the RVOT obstruction and forcing deoxygenated blood through the VSD into the systemic circulation. Acute management focuses on reversing this shunt. Knee-chest positioning increases SVR. Pharmacologically, supplemental oxygen promotes pulmonary vasodilation (decreasing right-sided resistance). Intravenous morphine is critical as it diminishes the respiratory drive, calms the patient, and decreases sympathetic output, which directly relaxes the dynamic RVOT spasm.

Step-by-Step Solution

1
Analyze the clinical presentation and physical exam findings.
The patient is a 10-month-old with sudden onset cyanosis triggered by crying, relieved by knee-chest positioning, with a harsh systolic ejection murmur at the left upper sternal border.
Identifying the classic signs of a hypercyanotic ('Tet') spell in a patient with undiagnosed Tetralogy of Fallot is essential for selecting the correct management.
2
Determine the underlying pathophysiology of the acute episode.
The episode is caused by dynamic spasm of the right ventricular outflow tract (RVOT), which increases resistance and forces deoxygenated blood across the ventricular septal defect (VSD) into the systemic circulation.
Understanding the mechanism dictates which pharmacologic interventions will help versus which will cause harm.
3
Select the appropriate pharmacologic intervention to reverse the right-to-left shunt.
Administration of supplemental oxygen and intravenous morphine.
Oxygen reduces pulmonary vascular resistance. Morphine acts to decrease respiratory drive, alleviate anxiety, and reduce sympathetic tone, thereby relaxing the infundibular spasm.

Key Concept

Pathophysiology and acute management of hypercyanotic spells in Tetralogy of Fallot.
Estimated Time:1m 15s
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Topics

Pediatric Cardiovascular Disorders

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