Practice exercise (made-up values, not clinical guidance). An 84 kg patient needs 1.8 g of protein per kg a day. The tube feed contains 63 g of protein per litre and runs at 50 mL/h for 24 hours a day. How many grams of extra protein ΔP a day are still needed? Round to one decimal place.
84 kg1.8 g/kg/day63 g/L50 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 176 cm tall and weighs 140 kg. The practice protocol gives 12 kcal/kg of actual body weight per day if the BMI is 30–50 kg/m², and 23 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 12-hour shift. The IV infusion ran at the rate shown for the whole shift. Find the fluid balance B = intake − output in mL (a negative answer means a net loss). Count ice chips as half their volume.
Practice exercise (made-up values, not clinical guidance). A 500 mL bag was started at 11:30 and runs by pump at 60 mL/h. How many mL V are left in the bag at 14:30?
500 mL60 mL/h11:30 → 14:30
V = mL
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: ΔP = 75.6 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
1.8·84 = 151.2 g/day
Protein from the feed
50·24 = 1200 mL = 1.2 L
1.2·63 = 75.6 g/day
Shortfall
ΔP = 151.2 − 75.6 = 75.6 g/day
Answer
ΔP = 75.6 g/day
2.Enteral & parenteral nutrition calculations
Answer: E = 1680 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 = 140/1.76² = 45.2 kg/m²
Energy goal
BMI 30–50: kcal per kg of actual body weight.
E = 12·140 = 1680 kcal/day
Answer
E = 1680 kcal/day
3.IV fluids & fluid balance
Answer: B = 895 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.
Total intake
oral: 100 + 100 = 200 mL
ice chips: 240/2 = 120 mL
IV infusion: 125·12 = 1500 mL
IV antibiotic: 1·100 = 100 mL
total intake = 1920 mL
Total output
225 + 300 + 500 = 1025 mL
Balance
B = 1920 − 1025 = 895 mL
Answer
B = 895 mL
Positive: more fluid went in than came out.
4.IV fluids & fluid balance
Answer: V = 320 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.