Final answer:
The most important initial action for the nurse to take is to stop the infusion immediately and remove the IV catheter. Assessing the client's arm for swelling and discoloration and administering a non-opioid pain reliever should also be done.
Step-by-step explanation:
The initial action that is most important for the nurse to take in this situation is A) Stop the infusion immediately and remove the IV catheter. Infiltration occurs when an IV fluid leaks into the surrounding tissue instead of flowing into the vein. In this case, the client is experiencing excruciating arm pain, which could be a result of the infiltrated normal saline. By stopping the infusion and removing the IV catheter, further damage and pain can be prevented. After stopping the infusion and removing the IV catheter, the nurse should then assess the client's arm for swelling and discoloration (C) Assess the client's arm for swelling and discoloration.) to determine the extent of the infiltration. Administering a non-opioid pain reliever (B) Administer a non-opioid pain reliever to alleviate the discomfort.) may also be necessary to provide immediate relief to the client. However, the most critical action at this stage is to stop the infusion and remove the catheter.