A 1-hour-old neonate with prenatally diagnosed tetralogy of Fallot is admitted to the neonatal intensive care unit with cyanosis. The mother is a 28-year-old gravida 3 para 2 who received routine prenatal care. The patient was born via spontaneous vaginal delivery at 35 weeks gestation. Initial Apgar scores are 5 and 7 at 1 and 5 minutes after birth, respectively. The neonate's lips, fingers, and toes appear cyanotic. This patient should be immediately treated with a medication producing which of the following effects?

Question

A 1-hour-old neonate with prenatally diagnosed tetralogy of Fallot is admitted to the neonatal intensive care unit with cyanosis.  The mother is a 28-year-old gravida 3 para 2 who received routine prenatal care.  The patient was born via spontaneous vaginal delivery at 35 weeks gestation.  Initial Apgar scores are 5 and 7 at 1 and 5 minutes after birth, respectively.  The neonate's lips, fingers, and toes appear cyanotic.  This patient should be immediately treated with a medication producing which of the following effects?

Quizplus · Accepted Answer

11ec160b_3aa2_ed48_9249_a9d7d838cd57_MD0001_00 Tetralogy of Fallot (TOF) is a cyanotic, congenital heart defect characterized by pulmonary stenosis, an overriding aorta, right ventricular hypertrophy, and a ventricular septal defect. When pulmonary stenosis is severe, TOF is a ductal-dependent lesion that relies on the patency of the ductus arteriosus (DA) for adequate oxygenation. The DA is a fetal vascular structure that connects the main pulmonary artery and aorta. In utero, blood (which is oxygenated by the placenta) bypasses the lungs by flowing from the pulmonary artery through the DA to the aorta. After birth, the lungs fill with oxygen and pulmonary vascular resistance decreases, causing the direction of flow through the DA to reverse (ie, from aorta to pulmonary artery). DA patency is maintained by circulating prostaglandin released by the placenta; after birth, prostaglandin production stops, and the DA starts closing. In severe TOF, critical pulmonary stenosis or atresia limits blood flow from the right side of the heart to the pulmonary circulation for oxygenation. Instead, blood reaches the pulmonary vascular bed via retrograde flow from the aorta through the DA. Without flow through the DA, affected neonates are unable to oxygenate blood. These patients are cyanotic after birth, as in this neonate, and require immediate administration of prostaglandin E1 to maintain patency of the DA. (Choice A) Heart failure medications that reduce preload (eg, diuretics) decrease left ventricular end diastolic pressure. This decrease would not improve right ventricular outflow tract obstruction or increase retrograde blood flow through the DA in patients with TOF. (Choice B) Administration of pulmonary surfactant can improve lung compliance in preterm neonates with respiratory distress syndrome. Because the primary pathology in TOF is cardiac rather than pulmonary, surfactant will not improve oxygenation. (Choice C) Increased pulmonary vascular resistance would worsen the pathophysiology of TOF by decreasing blood flow from the aorta through the DA into the lungs. (Choice E) Hydroxyurea increases fetal hemoglobin production, thereby improving the oxygen carrying capacity of blood in sickle cell anemia. In TOF, oxygenation is impaired due to inadequate pulmonary blood flow from right ventricular outflow tract obstruction. Educational objective: Severe tetralogy of Fallot is a ductal-dependent lesion that requires blood flow through the ductus arteriosus (from the aorta to the pulmonary artery) for adequate oxygenation. Prostaglandin E1 prevents closure of the ductus arteriosus and should be immediately administered to all cyanotic neonates with suspected ductal-dependent lesions. __________ References: Congenital heart disease requiring maintenance of ductus arteriosus in critically ill newborns admitted at a tertiary neonatal intensive care unit. (http://www.ncbi.nlm.nih.gov/pubmed/29967858)

A 1-Hour-Old Neonate with Prenatally Diagnosed Tetralogy of Fallot Is