Practice exercise (made-up values, not clinical guidance). A 51 kg patient has a fluid goal of 35 mL/kg/day and receives all fluid through a feeding tube. The formula is 81% free water and runs at 80 mL/h for 20 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.
51 kg35 mL/kg/day81%80 mL/h · 20 hevery 8 h
V = mL
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). A critically ill man is 171 cm tall and weighs 109 kg. The practice protocol gives 13 kcal/kg of actual body weight per day if the BMI is 30–50 kg/m², and 24 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 IV infusion ran at the rate shown for the whole shift. Find the fluid balance B = intake − output in mL (a negative answer means a net loss).
Practice exercise (made-up values, not clinical guidance). A 1000 mL bag runs by pump at 125 mL/h. At 09:30, 100 mL have already been infused. How many hours t until the bag is empty? Round to one decimal place.
1000 mL100 mL infused125 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: V = 163 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
35·51 = 1785 mL/day
Free water from the formula
80·20 = 1600 mL
1600·0.81 = 1296 mL
Water still needed
1785 − 1296 = 489 mL/day
Volume per flush
24/8 = 3 flushes
V = 489/3 = 163 mL
Answer
V = 163 mL
2.Enteral & parenteral nutrition calculations
Answer: E = 1417 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 = 109/1.71² = 37.28 kg/m²
Energy goal
BMI 30–50: kcal per kg of actual body weight.
E = 13·109 = 1417 kcal/day
Answer
E = 1417 kcal/day
3.IV fluids & fluid balance
Answer: B = 25 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.
Total intake
oral: 200 + 150 = 350 mL
IV infusion: 75·8 = 600 mL
IV antibiotic: 2·50 = 100 mL
total intake = 1050 mL
Total output
275 + 250 + 400 + 100 = 1025 mL
Balance
B = 1050 − 1025 = 25 mL
Answer
B = 25 mL
Positive: more fluid went in than came out.
4.IV fluids & fluid balance
Answer: t = 7.2 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 − 100 = 900 mL
Time
t = 900/125 = 7.2 h
Answer
t = 7.2 h
That is about 7 h 12 min, so the bag runs out at about 16:42.