A client presents with a warm, red, and tender IV site. What is the most likely cause of these signs?

The most likely cause of a warm, red, and tender IV site is phlebitis. Phlebitis refers to the inflammation of a vein, often related to intravenous therapy. This condition can develop when the vein reacts to the presence of the catheter or the infusate, leading to inflammation, which presents with warmth, redness, and tenderness at the site.

Infection typically involves more systemic symptoms like fever and would often show signs of spreading beyond the IV site. Chemical irritation can occur, usually resulting from the infusate being irritating to the vein but often does not present with the same level of warmth or redness. Hematoma formation typically presents as a localized swelling and discoloration around the site due to blood accumulation, but not necessarily significant warmth or redness unless there’s ongoing irritation or inflammation.

Therefore, the symptoms described strongly suggest phlebitis as the most probable cause.