Final answer:
When restraining a violent client, ensuring that the restraints are properly applied is the most important intervention for the safety and well-being of the patient.
Step-by-step explanation:
The most important nursing intervention when restraining a violent client is checking that the restraints have been applied correctly. This ensures the safety and well-being of the patient, preventing potential harm such as circulation impairment or breathing difficulties. Additionally, while it is important to review facility policies and to be prepared with medication if necessary, the immediate priority is the proper application of restraints. Lastly, attending to basic needs such as asking if the client needs to use the bathroom or is thirsty should be addressed promptly, but only after confirming that restraints are secure and the situation is under control.