A full-term newborn is evaluated in the delivery room due to mild tachypnea and cyanosis immediately after birth. Fetal ultrasonography performed during pregnancy revealed transposition of the great arteries. Heart rate and blood pressure are normal. Oxygen saturation is 72%. Cyanosis is apparent in the hands, feet, lips, and tongue. Peripheral pulses are strong. Bedside echocardiography confirms the prenatal diagnosis; there is also a small patent foramen ovale and a small patent ductus arteriosus. Definitive surgical correction of the main congenital abnormality is planned. Pending definitive repair, which of the following temporary measures would be most likely to improve this patient's condition?

Question

A full-term newborn is evaluated in the delivery room due to mild tachypnea and cyanosis immediately after birth.  Fetal ultrasonography performed during pregnancy revealed transposition of the great arteries.  Heart rate and blood pressure are normal.  Oxygen saturation is 72%.  Cyanosis is apparent in the hands, feet, lips, and tongue.  Peripheral pulses are strong.  Bedside echocardiography confirms the prenatal diagnosis; there is also a small patent foramen ovale and a small patent ductus arteriosus.  Definitive surgical correction of the main congenital abnormality is planned.  Pending definitive repair, which of the following temporary measures would be most likely to improve this patient's condition?

Quizplus · Accepted Answer

11ec160b_3aa4_25ca_9249_7582ccf362d2_MD0001_00 Transposition of the great arteries (TGA) is a cyanotic congenital heart defect caused by abnormal spiraling of the conotruncal septum, which divides the truncus arteriosus into the aorta and the pulmonary artery. The result is abnormal connections of the right ventricle to the aorta and the left ventricle to the pulmonary artery. As a result, oxygenated blood cycles through the left side of the heart to the pulmonary circulation and back while deoxygenated blood cycles through the right side of the heart to the systemic circulation and back; this results in neonatal cyanosis. TGA is incompatible with life without a left-to-right mixing lesion to provide the systemic circulation with partially oxygenated blood; a greater degree of intercirculatory mixing typically results in a lesser degree of hypoxemia. Examples of mixing lesions include patent ductus arteriosus, patent foramen ovale, and/or ventricular septal defect. Initial management of TGA therefore must ensure mixing of oxygenated and deoxygenated blood. For example, administration of prostaglandin E₁ maintains patency of the ductus arteriosus. Balloon atrial septostomy, which opens or widens the foramen ovale, may also be performed to allow for mixing at the atrial level and typically improves oxygen saturation immediately. (Choice A) Sinoatrial node ablation is sometimes used for treating tachyarrhythmias involving the sinoatrial node. However, the procedure would not improve this patient's hypoxemia. (Choice B) Because deoxygenated blood bypasses the pulmonary circulation and is delivered directly to the systemic circulation in TGA, supplemental oxygen administration does not significantly improve hypoxemia or cyanosis. (Choice C) Digoxin is a positive inotropic agent that can treat heart failure due to left ventricular systolic dysfunction (a finding not present on this patient's echocardiogram). Increased myocyte contractility would not improve this patient's oxygenation. (Choice E) Ligating the patent ductus arteriosus in a patient with TGA would decrease left-to-right shunting of blood and worsen hypoxemia and cyanosis. Educational objective: Transposition of the great arteries is characterized by parallel circulations of deoxygenated and oxygenated blood. Initial management includes maintaining a left-to-right mixing lesion (eg, patent ductus arteriosus, patent foramen ovale) to provide systemic circulation with partially oxygenated blood. __________ References: Transposition of the great arteries. (http://www.ncbi.nlm.nih.gov/pubmed/30860704)

A Full-Term Newborn Is Evaluated in the Delivery Room Due