Final answer:
The priority concern for a client experiencing thyroid storm is potential cardiac disturbances, such as a rapid heart rate and possible heart failure.
Step-by-step explanation:
A nurse caring for a client experiencing thyroid storm should prioritize potential cardiac disturbances. A thyroid storm is an extreme and life-threatening condition of hyperthyroidism with symptoms that can include a high fever, rapid heart rate, and even heart failure. In this scenario, cardiac disturbances pose an immediate threat to the patient's health and stability. Therefore, the priority concern for the client experiencing a thyroid storm would be D. Potential for cardiac disturbances.