Final answer:
The first intervention for a red and swollen venipuncture site during IV infusion should be to stop the infusion to prevent further complications, followed by notifying the physician.
Step-by-step explanation:
If a client receiving an IV infusion has a venipuncture site that is red and swollen, the nurse should prioritize patient safety first. The first intervention should be A. Stop the infusion. This action is essential to prevent further injury or complications like an infiltration or phlebitis. After stopping the IV, the nurse should assess the patient's condition and then notify the attending physician (B. Call the attending physician) about the situation, while also preparing to initiate a new IV line if necessary. Slowing down the infusion or applying a cold towel before stopping the IV could exacerbate the issue or delay critical care.