At what time should the next bag of IV solution be prepared if 500 mL remains at 1400?

To determine when the next bag of IV solution should be prepared, it's essential first to know the rate at which the IV solution is being infused. If 500 mL remains at 1400 (2:00 PM), we can calculate the time needed to infuse that remaining volume based on the infusion rate.

For instance, if the infusion rate is known (let's say, hypothetically, it's 125 mL/hour), you can calculate how long it will take to finish infusing the remaining 500 mL. Dividing 500 mL by 125 mL/hour gives 4 hours. Thus, the IV solution would finish infusing at 1800 (6:00 PM).

Considering this calculation, preparing the next bag of IV solution 30-60 minutes prior to the completion of the current infusion ensures that the patient does not experience a delay in their therapy. Hence, if the IV solution is due to finish at 1800, preparing the next bag around that time ensures continuity in treatment.

This reasoning confirms that the correct choice is 1800, as this preparation timing allows healthcare professionals to maintain the necessary treatment schedule without interruption.