Practice exercise (made-up values, not clinical guidance). A 57 kg patient needs 1.8 g of protein per kg a day. The tube feed contains 44 g of protein per litre and runs at 45 mL/h for 16 hours a day. How many grams of extra protein ΔP a day are still needed? Round to one decimal place.
57 kg1.8 g/kg/day44 g/L45 mL/h · 16 h
ΔP = g/day
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). A critically ill woman is 162 cm tall and weighs 116 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 IV infusion ran at the rate shown for the whole shift. Find the total intake I in mL.
soup: 180 mLjuice: 150 mLmilk: 240 mLIV infusion: 125 mL/h × 12 hIV antibiotic: 1 × 50 mL
I = mL
4.IV fluids & fluid balanceHard
Practice exercise (made-up values, not clinical guidance). A 500 mL infusion starts at 15:30 at 125 mL/h. After 2 hours the rate is changed to 200 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 · 2 h200 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: ΔP = 70.9 g/day
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.
Protein needed
1.8·57 = 102.6 g/day
Protein from the feed
45·16 = 720 mL = 0.72 L
0.72·44 = 31.68 g/day
Shortfall
ΔP = 102.6 − 31.68 = 70.92 ≈ 70.9 g/day
Answer
ΔP = 70.9 g/day
2.Enteral & parenteral nutrition calculations
Answer: E = 1624 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 = 116/1.62² = 44.2 kg/m²
Energy goal
BMI 30–50: kcal per kg of actual body weight.
E = 14·116 = 1624 kcal/day
Answer
E = 1624 kcal/day
3.IV fluids & fluid balance
Answer: I = 2120 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: 180 + 150 + 240 = 570 mL
IV infusion: 125·12 = 1500 mL
IV antibiotic: 1·50 = 50 mL
I = 2120 mL
Answer
I = 2120 mL
4.IV fluids & fluid balance
Answer: t = 3.3 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
125·2 = 250 mL
500 − 250 = 250 mL left
Second part
250/200 = 1.25 h
Total time
t = 2 + 1.25 = 3.25 ≈ 3.3 h
Answer
t = 3.3 h
That is about 3 h 15 min, so the bag runs out at about 18:45.