During a routine follow-up visit at the pediatric clinic, a 5-day-old boy is noted to be p… — USMLE Step 2 CK

During a routine follow-up visit at the pediatric clinic, a $5$ -day-old boy is noted to be profoundly lethargic with increased work of breathing. The mother reports that he has been sweating profusely during attempts to breastfeed over the last $12$ hours and has not produced a wet diaper since yesterday. The pregnancy and term delivery were uncomplicated, and he was discharged home at $48$ hours of life without any apparent issues. Vital signs show a temperature of $36.5^\circ\text{C}$ ( $97.7^\circ\text{F}$ ), heart rate of $190/\text{min}$ , and respiratory rate of $72/\text{min}$ . Blood pressure is $88/54 \text{ mm Hg}$ in the right upper extremity and $48/30 \text{ mm Hg}$ in the left lower extremity. Physical examination reveals a mottled, poorly responsive neonate with significant subcostal retractions and nasal flaring. Auscultation of the chest demonstrates a prominent parasternal heave, a harsh systolic murmur heard best over the left paravertebral interscapular area, and diffuse bilateral crackles. Palpation reveals bounding brachial pulses, but the femoral pulses are completely imperceptible. Pulse oximetry indicates an oxygen saturation of $97\%$ on the right hand and $84\%$ on the right foot. Arterial blood gas reveals a pH of $7.12$ , $pCO_2$ of $32 \text{ mm Hg}$ , and $HCO_3^-$ of $10 \text{ mEq/L}$ . Which of the following is the most appropriate initial step in the management of this patient?

A
Intravenous administration of sodium bicarbonate
B
Initiation of intravenous vancomycin and ceftriaxone
Continuous infusion of prostaglandin E1Cevap
D
Administration of nebulized albuterol
E
Immediate surgical exploration of the abdomen

Cevap

Continuous infusion of prostaglandin E1

The clinical presentation of severe shock, differential cyanosis (normal oxygen saturation in the right hand, low in the lower extremities), absent femoral pulses, and severe metabolic acidosis in a

5

-day-old neonate is highly characteristic of critical coarctation of the aorta. In this ductal-dependent lesion, systemic perfusion to the lower body relies heavily on a patent ductus arteriosus. As the ductus physiologically closes (typically around days

2

5

of life), lower extremity perfusion is abruptly compromised, leading to acute increased left ventricular afterload, heart failure, cardiogenic shock, and lactic acidosis. The most critical initial intervention is the administration of exogenous prostaglandin E1 to maintain or reopen ductal patency, rapidly restoring systemic blood flow and stabilizing the patient until definitive surgical repair can be performed.

Adım Adım Çözüm

Analyze the vital signs and physical examination findings.

The neonate demonstrates profound shock, severe metabolic acidosis, and specific discrepancies between the upper and lower extremities (higher blood pressure and oxygen saturation in the right arm compared to the legs, along with bounding brachial pulses and absent femoral pulses).

Identifying the anatomic gradient of perfusion is critical for localizing the exact site of pathology in a critically ill neonate.

Correlate the clinical presentation with the patient's age and pathophysiology.

The timeline (

5

days of life) corresponds perfectly with the normal physiologic closure of the ductus arteriosus. The findings indicate critical coarctation of the aorta, a ductal-dependent lesion where lower body perfusion is lost once the ductus closes.

Understanding the timeline of transition from fetal to neonatal circulation explains the sudden cardiovascular collapse in a previously healthy-appearing newborn.

Determine the most appropriate initial life-saving intervention.

Administration of a medication to reopen and maintain the patency of the ductus arteriosus is required to restore systemic blood flow.

Prostaglandin E1 (alprostadil) is the definitive medical therapy to stabilize patients with ductal-dependent systemic blood flow prior to surgical correction.

Anahtar Kavram

Critical coarctation of the aorta presents with cardiogenic shock, absent lower extremity pulses, and differential cyanosis when the ductus arteriosus closes in the first week of life; the life-saving initial treatment is a continuous infusion of prostaglandin E1.

Soru

Cevap

Adım Adım Çözüm

Anahtar Kavram

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