For a four-hour treatment, if a patient’s preweight is 72 kg and the target dry weight is 70 kg, the amount of fluid to be removed is best expressed as what rate in mL per hour?

For a four-hour treatment, if a patient’s preweight is 72 kg and the target dry weight is 70 kg, the amount of fluid to be removed is best expressed as what rate in mL per hour?

• A. 1000 mL/hour
• B. 250 mL/hour
• C. 750 mL/hour
• D. 500 mL/hour

Answer: (D)

Determine how much fluid to remove and over how long. The fluid to be removed equals the difference between preweight and target dry weight: 72 kg − 70 kg = 2 kg, which is about 2 liters. Over a four-hour treatment, the ultrafiltration rate is 2 L ÷ 4 h = 0.5 L/h, i.e., 500 mL per hour. So the best expression is 500 mL/hour. This uses the idea that 1 kg of weight corresponds to roughly 1 liter of fluid, and the rate is the hourly amount removed.

Determine how much fluid to remove and over how long. The fluid to be removed equals the difference between preweight and target dry weight: 72 kg − 70 kg = 2 kg, which is about 2 liters. Over a four-hour treatment, the ultrafiltration rate is 2 L ÷ 4 h = 0.5 L/h, i.e., 500 mL per hour. So the best expression is 500 mL/hour. This uses the idea that 1 kg of weight corresponds to roughly 1 liter of fluid, and the rate is the hourly amount removed.