Final answer:
The patient with an IV site that is cool, pale, and swollen is likely experiencing infiltration, where the IV fluid is leaking into the surrounding tissue.
Step-by-step explanation:
If a patient's IV site is cool, pale, and swollen, and the solution is not infusing, we can determine that the patient is likely experiencing infiltration. This occurs when IV fluid leaks into the surrounding tissue rather than flowing into the vein. In contrast, an infection would typically present with warmth and redness, phlebitis would cause pain and redness along the vein, and thrombosis would likely produce a palpable venous cord and block the flow of fluid entirely without causing swelling outside the vein. Infiltration happens when the IV solution leaks into the surrounding tissues instead of entering the bloodstream.