Final answer:
The nurse should limit the amount of caffeine on the client's dietary trays due to the prescription for a CNS stimulant. Caffeine is a CNS stimulant that blocks the action of adenosine, a neurotransmitter that promotes sleep.
Step-by-step explanation:
The client's prescription for a central nervous system (CNS) stimulant indicates that the nurse needs to limit the amount of caffeine on the client's dietary trays. Caffeine is a CNS stimulant that blocks the action of adenosine, a neurotransmitter that promotes sleep. By limiting the amount of caffeine, the nurse ensures that the client's CNS is not further stimulated, which could disrupt their sleep patterns.