Practice exercise (made-up values, not clinical guidance). An 81 kg adult (BMI below 30) needs 25 kcal/kg/day. The tube feed provides 1 kcal/mL and runs by pump for 24 hours a day. At what rate R do you set the pump, in mL/h? Round to the nearest whole number.
81 kg25 kcal/kg/day1 kcal/mL24 h
R = mL/h
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). A critically ill man is 166 cm tall and weighs 143 kg. The practice protocol gives 13 kcal/kg of actual body weight per day if the BMI is 30–50 kg/m², and 23 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). Count ice chips as half their volume.
Practice exercise (made-up values, not clinical guidance). A 1000 mL bag runs by pump at 120 mL/h. At 21:30, 800 mL have already been infused. How many hours t until the bag is empty? Round to one decimal place.
1000 mL800 mL infused120 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: R = 84 mL/h
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.
Energy needed
E = 25·81 = 2025 kcal/day
Daily volume
V = 2025/1 = 2025 mL/day
Pump rate
R = 2025/24 = 84.38 ≈ 84 mL/h
Answer
R = 84 mL/h
2.Enteral & parenteral nutrition calculations
Answer: E = 1433 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 = 143/1.66² = 51.89 kg/m²
Ideal body weight (Devine)
166 cm/2.54 = 65.35 in
IBW = 50 + 2.3·(65.35 − 60) = 62.31 kg
Energy goal
BMI above 50: kcal per kg of ideal body weight.
E = 23·62.31 = 1433 kcal/day
Answer
E = 1433 kcal/day
3.IV fluids & fluid balance
Answer: B = −400 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: 100 + 120 = 220 mL
ice chips: 240/2 = 120 mL
IV infusion: 60·8 = 480 mL
IV antibiotic: 1·50 = 50 mL
total intake = 870 mL
Total output
375 + 450 + 325 + 120 = 1270 mL
Balance
B = 870 − 1270 = −400 mL
Answer
B = −400 mL
Negative: the patient lost more fluid than went in.
4.IV fluids & fluid balance
Answer: t = 1.7 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 − 800 = 200 mL
Time
t = 200/120 = 1.667 ≈ 1.7 h
Answer
t = 1.7 h
That is about 1 h 40 min, so the bag runs out at about 23:10.