One and a half litres of D5% in 1/5 normal saline is to be given over 20 hours. What is the required flow rate in mL per hour?

One and a half litres of D5% in 1/5 normal saline is to be given over 20 hours. What is the required flow rate in mL per hour?

• A. 75 mL/h
• B. 60 mL/h
• C. 90 mL/h
• D. 100 mL/h

Answer: (A)

Flow rate equals the total volume to be delivered divided by the time over which it’s given. Here, 1.5 litres is the volume, which is 1500 mL, to be given over 20 hours. So the rate is 1500 mL ÷ 20 h = 75 mL per hour. The solution’s composition (D5% in NS) doesn’t affect the calculation—only the volume and the duration determine the flow rate. A quick check: 75 mL/h × 20 h = 1500 mL, which matches the prescribed volume. Therefore, the required flow rate is 75 mL/h.

Flow rate equals the total volume to be delivered divided by the time over which it’s given. Here, 1.5 litres is the volume, which is 1500 mL, to be given over 20 hours. So the rate is 1500 mL ÷ 20 h = 75 mL per hour. The solution’s composition (D5% in NS) doesn’t affect the calculation—only the volume and the duration determine the flow rate. A quick check: 75 mL/h × 20 h = 1500 mL, which matches the prescribed volume. Therefore, the required flow rate is 75 mL/h.