What term refers to a catheter that is completely implanted under the skin?

The term that refers to a catheter that is completely implanted under the skin is "implanted port." An implanted port is a type of central venous access device that is placed under the skin, allowing for easy access to the bloodstream without the need for repeated needle sticks. This device consists of a small reservoir connected to a catheter, which is placed into a large vein. The port is designed to be accessed using a special needle that punctures the skin over the port when needed for medication administration, blood draws, or other medical procedures.

An intra-arterial cannula is typically used for direct access to an artery and is not entirely implanted under the skin. A central venous access device, while it can include implanted ports, also encompasses other forms that may remain external. The term "internal catheter" is not a commonly recognized designation for a completely implanted device, which can lead to confusion in identifying the most appropriate terminology. Thus, the most accurate term among the choices provided is implanted port.