Final answer:
The nurse should label the damaged IV pump and send it for repair to maintain safety and prevent harm to the patient.
Step-by-step explanation:
The best action for the nurse to take when noticing a cracked electrical cord on an IV infusion pump is to clearly label the pump and send it for repair. Using a damaged electrical device poses a risk for electrical shock or malfunction of the equipment, which could lead to inadequate therapy or harm to the patient. It is essential for the nurse to ensure a safe environment for the patient by removing the defective equipment from use until it can be properly serviced.