Practice exercise (made-up values, not clinical guidance). A 95 kg patient needs 1.3 g of protein per kg a day. The tube feed contains 40 g of protein per litre and runs at 70 mL/h for 18 hours a day. A protein powder supplies 7 g of protein per scoop. How many scoops n a day are needed to cover the shortfall? Round up to a whole scoop.
95 kg1.3 g/kg/day40 g/L70 mL/h · 18 h7 g/scoop
n =
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). A critically ill woman is 175 cm tall and weighs 99 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 8-hour shift. The patient weighs 106 kg. Find the average urine output U in mL/kg/h. Round to two decimal places.
106 kg8 hurine: 150 mLurine: 425 mLwound drain: 80 mL
U = mL/kg/h
4.IV fluids & fluid balanceHard
Practice exercise (made-up values, not clinical guidance). A 500 mL infusion starts at 14:30 at 125 mL/h. After 2 hours the rate is changed to 50 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 h50 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: n = 11
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
1.3·95 = 123.5 g/day
Protein from the feed
70·18 = 1260 mL = 1.26 L
1.26·40 = 50.4 g/day
Shortfall
ΔP = 123.5 − 50.4 = 73.1 g
Scoops
73.1/7 = 10.44 → n = 11
Answer
n = 11
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 = 99/1.75² = 32.33 kg/m²
Ideal body weight (Devine)
175 cm/2.54 = 68.9 in
IBW = 45.5 + 2.3·(68.9 − 60) = 65.96 kg
Protein goal
BMI 30 to under 40: 2 g per kg of ideal body weight.
P = 2·65.96 = 131.9 ≈ 132 g/day
Answer
P = 132 g/day
3.IV fluids & fluid balance
Answer: U = 0.68 mL/kg/h
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 urine
150 + 425 = 575 mL
Per kilogram per hour
U = 575/(106·8) = 0.6781 ≈ 0.68 mL/kg/h
Answer
U = 0.68 mL/kg/h
4.IV fluids & fluid balance
Answer: t = 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.
First part
125·2 = 250 mL
500 − 250 = 250 mL left
Second part
250/50 = 5 h
Total time
t = 2 + 5 = 7 h
Answer
t = 7 h
That is about 7 h 00 min, so the bag runs out at about 21:30.