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 80 mL/h for 18 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%80 mL/h · 18 hevery 4 h
V = mL
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). A critically ill woman is 162 cm tall and weighs 146 kg. The practice protocol gives 2 g of protein per kg of ideal body weight (Devine) per day if the BMI is 30 to under 40 kg/m², and 2.5 g/kg of ideal body weight per day if the BMI is 40 kg/m² or more. Find the protein goal P in g/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 104 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 was started at 08:00 and runs by pump at 120 mL/h. How many mL V are left in the bag at 15:30?
1000 mL120 mL/h08:00 → 15:30
V = mL
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: V = 197 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
80·18 = 1440 mL
1440·0.76 = 1094 mL
Water still needed
2275 − 1094 = 1181 mL/day
Volume per flush
24/4 = 6 flushes
V = 1181/6 = 196.8 ≈ 197 mL
Answer
V = 197 mL
2.Enteral & parenteral nutrition calculations
Answer: P = 135 g/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). The protein goal is 2 g/kg of ideal body weight per day for BMI 30–40 and up to 2.5 g/kg of ideal body weight per day for BMI 40 and above. The numbers are for practice only; at the bedside always follow local protocols and have high-risk doses double-checked.
Body mass index
BMI = 146/1.62² = 55.63 kg/m²
Ideal body weight (Devine)
162 cm/2.54 = 63.78 in
IBW = 45.5 + 2.3·(63.78 − 60) = 54.19 kg
Protein goal
BMI 40 or more: 2.5 g per kg of ideal body weight.
P = 2.5·54.19 = 135.5 ≈ 135 g/day
Answer
P = 135 g/day
3.IV fluids & fluid balance
Answer: U = 1.92 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
325 + 500 + 475 + 300 = 1600 mL
Per kilogram per hour
U = 1600/(104·8) = 1.923 ≈ 1.92 mL/kg/h
Answer
U = 1.92 mL/kg/h
4.IV fluids & fluid balance
Answer: V = 100 mL
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.