Practice exercise (made-up values, not clinical guidance). An 88 kg patient needs 1.3 g of protein per kg a day. The tube feed contains 84 g of protein per litre and runs at 45 mL/h for 16 hours a day. How many grams of extra protein ΔP a day are still needed? Round to one decimal place.
88 kg1.3 g/kg/day84 g/L45 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 167 cm tall and weighs 99 kg. The practice protocol gives 12 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 45 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 150 mL/h. At 10:30, 50 mL have already been infused. How many hours t until the bag is empty? Round to one decimal place.
1000 mL50 mL infused150 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: ΔP = 53.9 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
1.3·88 = 114.4 g/day
Protein from the feed
45·16 = 720 mL = 0.72 L
0.72·84 = 60.48 g/day
Shortfall
ΔP = 114.4 − 60.48 = 53.92 ≈ 53.9 g/day
Answer
ΔP = 53.9 g/day
2.Enteral & parenteral nutrition calculations
Answer: E = 1188 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 = 99/1.67² = 35.5 kg/m²
Energy goal
BMI 30–50: kcal per kg of actual body weight.
E = 12·99 = 1188 kcal/day
Answer
E = 1188 kcal/day
3.IV fluids & fluid balance
Answer: U = 1.74 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
275 + 350 = 625 mL
Per kilogram per hour
U = 625/(45·8) = 1.736 ≈ 1.74 mL/kg/h
Answer
U = 1.74 mL/kg/h
4.IV fluids & fluid balance
Answer: t = 6.3 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 − 50 = 950 mL
Time
t = 950/150 = 6.333 ≈ 6.3 h
Answer
t = 6.3 h
That is about 6 h 20 min, so the bag runs out at about 16:50.