Practice exercise (made-up values, not clinical guidance). A 53 kg patient has a fluid goal of 30 mL/kg/day and receives all fluid through a feeding tube. The formula is 70% free water and runs at 65 mL/h for 24 hours a day. The rest of the fluid is given as water flushes every 8 hours. What volume V is each flush? Round to the nearest whole number.
53 kg30 mL/kg/day70%65 mL/h · 24 hevery 8 h
V = mL
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). A critically ill man is 183 cm tall and weighs 186 kg. The practice protocol gives 14 kcal/kg of actual body weight per day if the BMI is 30–50 kg/m², and 22 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 12-hour shift. The patient weighs 107 kg. Find the average urine output U in mL/kg/h. Round to two decimal places.
Practice exercise (made-up values, not clinical guidance). A 1000 mL bag runs by pump at 80 mL/h. At 12:00, 650 mL have already been infused. How many hours t until the bag is empty? Round to one decimal place.
1000 mL650 mL infused80 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: V = 166 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
30·53 = 1590 mL/day
Free water from the formula
65·24 = 1560 mL
1560·0.7 = 1092 mL
Water still needed
1590 − 1092 = 498 mL/day
Volume per flush
24/8 = 3 flushes
V = 498/3 = 166 mL
Answer
V = 166 mL
2.Enteral & parenteral nutrition calculations
Answer: E = 1710 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 = 186/1.83² = 55.54 kg/m²
Ideal body weight (Devine)
183 cm/2.54 = 72.05 in
IBW = 50 + 2.3·(72.05 − 60) = 77.71 kg
Energy goal
BMI above 50: kcal per kg of ideal body weight.
E = 22·77.71 = 1710 kcal/day
Answer
E = 1710 kcal/day
3.IV fluids & fluid balance
Answer: U = 0.9 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
450 + 375 + 325 = 1150 mL
Per kilogram per hour
U = 1150/(107·12) = 0.8956 ≈ 0.9 mL/kg/h
Answer
U = 0.9 mL/kg/h
4.IV fluids & fluid balance
Answer: t = 4.4 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.
Volume left
1000 − 650 = 350 mL
Time
t = 350/80 = 4.375 ≈ 4.4 h
Answer
t = 4.4 h
That is about 4 h 23 min, so the bag runs out at about 16:23.