Final answer:
The nurse should program the infusion pump to infuse at a rate of approximately 4 mL/min.
Step-by-step explanation:
To calculate the rate at which the nurse should program the infusion pump, we need to determine the volume of saline solution to be infused per minute. The infusion rate for the order to infuse 400mL 0.9% normal saline over 90 minutes is 267 mL/hour when rounded to the nearest whole number.
Given that the total volume is 400 mL and the total time is 90 minutes, we can use the formula:
Rate = Total Volume / Total Time
Rate = 400 mL / 90 minutes
Rate ≈ 4.44 mL/min
Therefore, the nurse should program the infusion pump to infuse at a rate of approximately 4 mL/min.