Final answer:
The most likely cause of swelling at a peripheral IV site is edema, which is the accumulation of excess water in the tissues. It can be caused by various factors including medical conditions, therapeutic drugs, pregnancy, injury, or allergic reactions.
Step-by-step explanation:
The most likely cause of swelling at a patient's peripheral IV site, as informed by a PCT (Patient Care Technician), is edema. Edema is the accumulation of excess water in the tissues and is most common in the soft tissues of the extremities. It can be caused by an underlying medical condition, certain therapeutic drugs, pregnancy, localized injury, or allergic reaction. To confirm the presence of edema in a limb, a quick test involves pressing a finger into the suspected area and checking if the depression persists after the finger is removed.