A 5-week-old boy is receiving care in the neonatal intensive care unit. The patient was born at 26 weeks gestation with a birth weight of 0.79 kg (1 lb 10 oz). Echocardiography reveals a patent ductus arteriosus and a dilated left atrium. The patient has moderate pulmonary edema. During surgical ligation of the ductus arteriosus, the surgeons perform a left-sided thoracotomy, visualize the ductus, and place a small metal clamp across the vessel. Which of the following changes is most likely to take place immediately after ligation?

Question

A 5-week-old boy is receiving care in the neonatal intensive care unit.  The patient was born at 26 weeks gestation with a birth weight of 0.79 kg (1 lb 10 oz).  Echocardiography reveals a patent ductus arteriosus and a dilated left atrium.  The patient has moderate pulmonary edema.  During surgical ligation of the ductus arteriosus, the surgeons perform a left-sided thoracotomy, visualize the ductus, and place a small metal clamp across the vessel.  Which of the following changes is most likely to take place immediately after ligation?

Quizplus · Accepted Answer

11ec160b_3a98_b400_9249_514bb6e02cb3_MD0001_00 A patent ductus arteriosus (PDA) allows blood to flow from the aorta into the relatively low-pressure pulmonary artery. When a PDA persists longer than the initial postnatal period (eg, >48 hours), the left-to-right shunt causes overcirculation of the lungs and left side of the heart, which can ultimately lead to left-sided heart failure and pulmonary edema. Closure of a persistent PDA can be achieved with a medication that inhibits prostaglandin synthesis (eg, indomethacin, ibuprofen) or by surgical ligation. When the PDA shunt is ablated during surgery, there is an immediate reduction in pulmonary venous return to the left atrium (ie, decreased LV preload) and increased diastolic blood pressure in the aorta (ie, increased LV afterload). The combination of these two immediate changes can result in an acute decrease in LV stroke volume and cardiac output (Choice D). (Choices A, B, and E) In patients with a left-to-right shunt through a PDA, the increased volume load is handled entirely by the left ventricle. The right ventricle receives deoxygenated blood from the body via the superior and inferior vena cava and pumps that blood to the pulmonary artery. This does not change when the PDA is closed, so there are no postligation changes to preload, afterload, or cardiac output of the right ventricle. Educational objective: Closure of a patent ductus arteriosus results in decreased pulmonary venous return to the left atrium (decreased left ventricular preload) and increased diastolic blood pressure in the aorta (increased left ventricular afterload). Together, these changes acutely lower left ventricular stroke volume and cardiac output.

A 5-Week-Old Boy Is Receiving Care in the Neonatal Intensive