Practice exercise (made-up values, not clinical guidance). A 100 kg patient needs 1.3 g of protein per kg a day. The tube feed contains 63 g of protein per litre and runs at 55 mL/h for 24 hours a day. How many grams of extra protein ΔP a day are still needed? Round to one decimal place.
100 kg1.3 g/kg/day63 g/L55 mL/h · 24 h
ΔP = g/day
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). A critically ill man is 183 cm tall and weighs 105 kg. The practice protocol gives 13 kcal/kg of actual body weight per day if the BMI is 30–50 kg/m², and 24 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 8-hour shift. The patient weighs 81 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 runs by pump at 60 mL/h. At 15:00, 600 mL have already been infused. How many hours t until the bag is empty? Round to one decimal place.
1000 mL600 mL infused60 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: ΔP = 46.8 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
1.3·100 = 130 g/day
Protein from the feed
55·24 = 1320 mL = 1.32 L
1.32·63 = 83.16 g/day
Shortfall
ΔP = 130 − 83.16 = 46.84 ≈ 46.8 g/day
Answer
ΔP = 46.8 g/day
2.Enteral & parenteral nutrition calculations
Answer: E = 1365 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 = 105/1.83² = 31.35 kg/m²
Energy goal
BMI 30–50: kcal per kg of actual body weight.
E = 13·105 = 1365 kcal/day
Answer
E = 1365 kcal/day
3.IV fluids & fluid balance
Answer: U = 1.04 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
450 + 225 = 675 mL
Per kilogram per hour
U = 675/(81·8) = 1.042 ≈ 1.04 mL/kg/h
Answer
U = 1.04 mL/kg/h
4.IV fluids & fluid balance
Answer: t = 6.7 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.
Volume left
1000 − 600 = 400 mL
Time
t = 400/60 = 6.667 ≈ 6.7 h
Answer
t = 6.7 h
That is about 6 h 40 min, so the bag runs out at about 21:40.