A nurse is preparing to measure an infant's vital signs. The nurse should use which of the following sites to assess a heart rate?

D. A client's blood pressure changes from 112/60 mm Hg to 90/54 mm Hg when standing.
A significant drop in blood pressure when changing positions from lying to standing may indicate orthostatic hypotension, which can be a sign of dehydration, blood loss, or other underlying medical issues. This can be a cause for concern, especially if the client is an adolescent, as it may lead to decreased perfusion of vital organs and may require immediate medical attention.

The other options are as follows:
A. A client who has a burn injury to an estimated 5% of his leg and is crying - While it's essential to assess and address the client's pain and comfort, this finding does not indicate an immediate need for medical attention. Pain management and wound care can be addressed based on the severity of the burn and the client's pain level.
B. A client who has an ankle fracture reports a pain level increase from 3 to 5 after initial ambulation - This finding is concerning, and the nurse should notify the provider to reassess pain management and evaluate for potential complications related to the fracture. However, it may not require immediate medical attention unless there are signs of severe pain or complications.
C. A client who is 1 day postoperative and has a temperature of 37.5° C (99.5° F) - A slight increase in temperature in the immediate postoperative period may not be unusual and can be attributed to the normal inflammatory response after surgery. The nurse should continue monitoring the client's temperature and report any further changes or additional signs of infection or complications to the provider.
Overall, while all findings should be addressed and managed appropriately, the significant drop in blood pressure (option D) should be reported immediately due to the potential implications for the client's overall health and well-being.

A patent ductus arteriosus (PDA) is a congenital heart defect associated with increased pulmonary blood flow. In normal fetal circulation, the ductus arteriosus allows blood to bypass the lungs since the baby receives oxygen from the mother's placenta. After birth, the ductus arteriosus should close, redirecting blood flow to the lungs for oxygenation. However, in some infants with PDA, the ductus arteriosus remains open, causing an abnormal connection between the aorta and the pulmonary artery. As a result, oxygenated blood from the aorta flows back into the pulmonary artery, increasing the workload on the lungs.

The other options are as follows:
A. Coarctation of the aorta - Coarctation of the aorta is a narrowing of the aorta, which obstructs blood flow and leads to increased blood pressure in the upper body and reduced blood flow to the lower body.
C. Tetralogy of Fallot - Tetralogy of Fallot is a combination of four heart defects that results in decreased pulmonary blood flow due to a ventricular septal defect (VSD), overriding aorta, pulmonary stenosis, and right ventricular hypertrophy.
D. Tricuspid atresia - Tricuspid atresia is a congenital heart defect where the tricuspid valve does not develop correctly, resulting in an absent or abnormal tricuspid valve. This defect prevents blood flow from the right atrium to the right ventricle and, therefore, reduces pulmonary blood flow.