Practice exercise (made-up values, not clinical guidance). A 75 kg patient needs 2 g of protein per kg a day. The tube feed contains 40 g of protein per litre and runs at 80 mL/h for 24 hours a day. How many grams of extra protein ΔP a day are still needed? Round to one decimal place.
75 kg2 g/kg/day40 g/L80 mL/h · 24 h
ΔP = g/day
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). A critically ill woman is 157 cm tall and weighs 117 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 12-hour shift. The IV infusion ran at the rate shown for the whole shift. Find the total intake I in mL.
milk: 240 mLjuice: 150 mLIV infusion: 100 mL/h × 12 hIV antibiotic: 2 × 100 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 75 mL/h. After 2 hours the rate is changed to 60 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 mL75 mL/h · 2 h60 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: ΔP = 73.2 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
2·75 = 150 g/day
Protein from the feed
80·24 = 1920 mL = 1.92 L
1.92·40 = 76.8 g/day
Shortfall
ΔP = 150 − 76.8 = 73.2 g/day
Answer
ΔP = 73.2 g/day
2.Enteral & parenteral nutrition calculations
Answer: P = 124 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 = 117/1.57² = 47.47 kg/m²
Ideal body weight (Devine)
157 cm/2.54 = 61.81 in
IBW = 45.5 + 2.3·(61.81 − 60) = 49.67 kg
Protein goal
BMI 40 or more: 2.5 g per kg of ideal body weight.
P = 2.5·49.67 = 124.2 ≈ 124 g/day
Answer
P = 124 g/day
3.IV fluids & fluid balance
Answer: I = 1790 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: 240 + 150 = 390 mL
IV infusion: 100·12 = 1200 mL
IV antibiotic: 2·100 = 200 mL
I = 1790 mL
Answer
I = 1790 mL
4.IV fluids & fluid balance
Answer: t = 7.8 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
75·2 = 150 mL
500 − 150 = 350 mL left
Second part
350/60 = 5.833 h
Total time
t = 2 + 5.833 = 7.833 ≈ 7.8 h
Answer
t = 7.8 h
That is about 7 h 50 min, so the bag runs out at about 23:20.