Final answer:
The priority nursing action for a client in a mixed episode of bipolar disorder is to monitor for escalating behavior to ensure the safety of the client and others.
Step-by-step explanation:
The priority nursing action when caring for a client experiencing a mixed episode of bipolar disorder in an acute mental health facility is to monitor the client for escalating behavior. Patients experiencing mixed episodes can present with rapidly changing emotions and energy levels, leading to unpredictable and potentially harmful behaviors. It is crucial to ensure the safety of the client and others, and closely observing for signs of escalation allows the nurse to intervene promptly if the client's behavior becomes dangerous. Other nursing actions, such as setting consistent limits, administering prescribed medications, and providing step-by-step instructions, are also important but are secondary to the immediate safety concerns associated with escalating behaviors.