A 3-month-old infant shows poor feeding and has a machine-like murmur. What should the nurse suspect?

In the case of a 3-month-old infant exhibiting poor feeding and a machine-like murmur, the most likely condition to suspect is Patent Ductus Arteriosus (PDA). PDA occurs when the ductus arteriosus, a blood vessel that normally closes shortly after birth, remains open. This persistent connection leads to abnormal blood flow between the aorta and the pulmonary artery.

The characteristic "machine-like" or continuous murmur is a hallmark sign of PDA, often described as a "bounding" or "whooshing" sound upon auscultation. This sound results from the continuous flow of blood from the high-pressure aorta into the lower-pressure pulmonary artery. Poor feeding in infants can occur due to the increased workload on the heart and inadequate energy for feeding, which is often a direct consequence of the complications arising from an unclosed ductus.

While other conditions may also present with symptoms affecting feeding or heart murmurs, they typically have different auscultatory features or additional signs that would guide diagnosis away from PDA. Thus, the signs presented—especially the machine-like murmur—strongly suggest that PDA is the most probable cause in this infant.