Practice exercise (made-up values, not clinical guidance). A 65 kg patient has a fluid goal of 35 mL/kg/day and receives all fluid through a feeding tube. The formula is 76% free water and runs at 65 mL/h for 20 hours a day. The rest of the fluid is given as water flushes every 4 hours. What volume V is each flush? Round to the nearest whole number.
65 kg35 mL/kg/day76%65 mL/h · 20 hevery 4 h
V = mL
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). A critically ill woman is 163 cm tall and weighs 134 kg. The practice protocol gives 11 kcal/kg of actual body weight per day if the BMI is 30–50 kg/m², and 25 kcal/kg of ideal body weight (Devine) per day if the BMI is above 50 kg/m². Find the energy goal E in kcal/day. Round to the nearest whole number.
Practice exercise (made-up values, not clinical guidance). The record shows a patient's intake and output for one 8-hour shift. The patient weighs 101 kg. Find the average urine output U in mL/kg/h. Round to two decimal places.
101 kg8 hurine: 200 mLurine: 175 mLurine: 150 mL
U = mL/kg/h
4.IV fluids & fluid balanceHard
Practice exercise (made-up values, not clinical guidance). A 1000 mL infusion starts at 06:00 at 125 mL/h. After 3 hours the rate is changed to 200 mL/h and is not changed again. How many hours t after the start will the bag be empty? Round to one decimal place.
1000 mL125 mL/h · 3 h200 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: V = 215 mL
Needs and free water: energy needs are often estimated as kcal/kg/day × weight and protein needs as g/kg/day × weight. A formula is only partly water, so its free water = volume × water fraction; water flushes make up the rest of the daily fluid goal. Ideal body weight (Devine): IBW = 50 kg + 2.3 kg for every inch over 5 feet (60 in) for men, and 45.5 kg + 2.3 kg per inch over 60 in for women; 1 in = 2.54 cm. The formula is meant for adults at least 152.4 cm (5 ft) tall. The numbers are for practice only; at the bedside always follow local protocols and have high-risk doses double-checked.
Fluid goal
35·65 = 2275 mL/day
Free water from the formula
65·20 = 1300 mL
1300·0.76 = 988 mL
Water still needed
2275 − 988 = 1287 mL/day
Volume per flush
24/4 = 6 flushes
V = 1287/6 = 214.5 ≈ 215 mL
Answer
V = 215 mL
2.Enteral & parenteral nutrition calculations
Answer: E = 1377 kcal/day
Ideal body weight (Devine): IBW = 50 kg + 2.3 kg for every inch over 5 feet (60 in) for men, and 45.5 kg + 2.3 kg per inch over 60 in for women; 1 in = 2.54 cm. The formula is meant for adults at least 152.4 cm (5 ft) tall. Obesity in critical illness (ASPEN/SCCM 2016): BMI = weight/height² (kg/m²). For BMI 30–50 the energy goal is 11–14 kcal/kg of actual body weight per day; above 50 it is 22–25 kcal/kg of ideal body weight per day. The numbers are for practice only; at the bedside always follow local protocols and have high-risk doses double-checked.
Body mass index
BMI = 134/1.63² = 50.43 kg/m²
Ideal body weight (Devine)
163 cm/2.54 = 64.17 in
IBW = 45.5 + 2.3·(64.17 − 60) = 55.1 kg
Energy goal
BMI above 50: kcal per kg of ideal body weight.
E = 25·55.1 = 1377 kcal/day
Answer
E = 1377 kcal/day
3.IV fluids & fluid balance
Answer: U = 0.65 mL/kg/h
Intake and output: intake counts everything that goes in (oral fluids, IV infusions, IV medications and flushes, tube feeds); ice chips count as half their volume. Output counts urine, drains, vomit and other losses. Balance = total intake − total output; a negative balance is a net loss. The numbers are for practice only; at the bedside always follow local protocols and have high-risk doses double-checked.
Total urine
200 + 175 + 150 = 525 mL
Per kilogram per hour
U = 525/(101·8) = 0.6498 ≈ 0.65 mL/kg/h
Answer
U = 0.65 mL/kg/h
4.IV fluids & fluid balance
Answer: t = 6.1 h
Infusion time: time (h) = volume to infuse (mL)/rate (mL/h); use the volume still left in the bag, not the bag size. Volume infused = rate × time. Convert decimal hours to hours and minutes with the fraction × 60 (0.5 h = 30 min, not 50 min). The numbers are for practice only; at the bedside always follow local protocols and have high-risk doses double-checked.
First part
125·3 = 375 mL
1000 − 375 = 625 mL left
Second part
625/200 = 3.125 h
Total time
t = 3 + 3.125 = 6.125 ≈ 6.1 h
Answer
t = 6.1 h
That is about 6 h 08 min, so the bag runs out at about 12:08.