Practice exercise (made-up values, not clinical guidance). A 68 kg patient needs 1.3 g of protein per kg a day. The tube feed contains 44 g of protein per litre and runs at 85 mL/h for 18 hours a day. How many grams of extra protein ΔP a day are still needed? Round to one decimal place.
68 kg1.3 g/kg/day44 g/L85 mL/h · 18 h
ΔP = g/day
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). A critically ill man is 170 cm tall and weighs 94 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. Count ice chips as half their volume.
Practice exercise (made-up values, not clinical guidance). A 1000 mL bag was started at 09:30 and runs by pump at 50 mL/h. How many mL V are left in the bag at 15:30?
1000 mL50 mL/h09:30 → 15:30
V = mL
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: ΔP = 21.1 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
1.3·68 = 88.4 g/day
Protein from the feed
85·18 = 1530 mL = 1.53 L
1.53·44 = 67.32 g/day
Shortfall
ΔP = 88.4 − 67.32 = 21.08 ≈ 21.1 g/day
Answer
ΔP = 21.1 g/day
2.Enteral & parenteral nutrition calculations
Answer: P = 132 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 = 94/1.7² = 32.53 kg/m²
Ideal body weight (Devine)
170 cm/2.54 = 66.93 in
IBW = 50 + 2.3·(66.93 − 60) = 65.94 kg
Protein goal
BMI 30 to under 40: 2 g per kg of ideal body weight.
P = 2·65.94 = 131.9 ≈ 132 g/day
Answer
P = 132 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 + 300 = 550 mL
ice chips: 200/2 = 100 mL
IV infusion: 50·12 = 600 mL
IV antibiotic: 1·100 = 100 mL
I = 1350 mL
Answer
I = 1350 mL
4.IV fluids & fluid balance
Answer: V = 700 mL
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.