Practice exercise (made-up values, not clinical guidance). A 60 kg patient has a fluid goal of 30 mL/kg/day and receives all fluid through a feeding tube. The formula is 76% free water and runs at 45 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.
60 kg30 mL/kg/day76%45 mL/h · 18 hevery 4 h
V = mL
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). A critically ill man is 166 cm tall and weighs 127 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 IV infusion ran at the rate shown for the whole shift. Find the total intake I in mL.
milk: 100 mLsoup: 150 mLIV infusion: 125 mL/h × 8 hIV antibiotic: 2 × 50 mL
I = mL
4.IV fluids & fluid balanceHard
Practice exercise (made-up values, not clinical guidance). A 500 mL infusion starts at 19:30 at 125 mL/h. After 3 hours the rate is changed to 80 mL/h and is not changed again. How many hours t after the start will the bag be empty? Round to one decimal place.
500 mL125 mL/h · 3 h80 mL/h
t = h
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
30·60 = 1800 mL/day
Free water from the formula
45·18 = 810 mL
810·0.76 = 615.6 mL
Water still needed
1800 − 615.6 = 1184 mL/day
Volume per flush
24/4 = 6 flushes
V = 1184/6 = 197.4 ≈ 197 mL
Answer
V = 197 mL
2.Enteral & parenteral nutrition calculations
Answer: P = 156 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 = 127/1.66² = 46.09 kg/m²
Ideal body weight (Devine)
166 cm/2.54 = 65.35 in
IBW = 50 + 2.3·(65.35 − 60) = 62.31 kg
Protein goal
BMI 40 or more: 2.5 g per kg of ideal body weight.
P = 2.5·62.31 = 155.8 ≈ 156 g/day
Answer
P = 156 g/day
3.IV fluids & fluid balance
Answer: I = 1350 mL
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.
Add the intake
oral: 100 + 150 = 250 mL
IV infusion: 125·8 = 1000 mL
IV antibiotic: 2·50 = 100 mL
I = 1350 mL
Answer
I = 1350 mL
4.IV fluids & fluid balance
Answer: t = 4.6 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
500 − 375 = 125 mL left
Second part
125/80 = 1.563 h
Total time
t = 3 + 1.563 = 4.563 ≈ 4.6 h
Answer
t = 4.6 h
That is about 4 h 34 min, so the bag runs out at about 00:04.