Practice exercise (made-up values, not clinical guidance). An 89 kg patient needs 2 g of protein per kg a day. The tube feed contains 84 g of protein per litre and runs at 90 mL/h for 16 hours a day. How many grams of extra protein ΔP a day are still needed? Round to one decimal place.
89 kg2 g/kg/day84 g/L90 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 168 cm tall and weighs 109 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 patient weighs 70 kg. Find the average urine output U in mL/kg/h. Round to two decimal places.
Practice exercise (made-up values, not clinical guidance). A 1000 mL bag was started at 07:15 and runs by pump at 50 mL/h. How many mL V are left in the bag at 09:15?
1000 mL50 mL/h07:15 → 09:15
V = mL
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: ΔP = 57 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
2·89 = 178 g/day
Protein from the feed
90·16 = 1440 mL = 1.44 L
1.44·84 = 121 g/day
Shortfall
ΔP = 178 − 121 = 57.04 ≈ 57 g/day
Answer
ΔP = 57 g/day
2.Enteral & parenteral nutrition calculations
Answer: P = 119 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 = 109/1.68² = 38.62 kg/m²
Ideal body weight (Devine)
168 cm/2.54 = 66.14 in
IBW = 45.5 + 2.3·(66.14 − 60) = 59.63 kg
Protein goal
BMI 30 to under 40: 2 g per kg of ideal body weight.
P = 2·59.63 = 119.3 ≈ 119 g/day
Answer
P = 119 g/day
3.IV fluids & fluid balance
Answer: U = 0.36 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 + 150 = 300 mL
Per kilogram per hour
U = 300/(70·12) = 0.3571 ≈ 0.36 mL/kg/h
Answer
U = 0.36 mL/kg/h
4.IV fluids & fluid balance
Answer: V = 900 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.