Practice exercise (made-up values, not clinical guidance). An 80 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 70 mL/h for 18 hours a day. How many grams of extra protein ΔP a day are still needed? Round to one decimal place.
80 kg1.3 g/kg/day63 g/L70 mL/h · 18 h
ΔP = g/day
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). A child who weighs 15 kg receives 12.5% dextrose at 33 mL/h. Find the glucose infusion rate GIR in mg/kg/min. Round to two decimal places.
15 kg12.5%33 mL/h
GIR = mg/kg/min
3.IV fluids & fluid balanceMedium
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 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 infusion starts at 13:00 at 125 mL/h. After 4 hours the rate is changed to 60 mL/h and is not changed again. How many hours t after the start will the bag be empty? Round to one decimal place.
1000 mL125 mL/h · 4 h60 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: ΔP = 24.6 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
1.3·80 = 104 g/day
Protein from the feed
70·18 = 1260 mL = 1.26 L
1.26·63 = 79.38 g/day
Shortfall
ΔP = 104 − 79.38 = 24.62 ≈ 24.6 g/day
Answer
ΔP = 24.6 g/day
2.Enteral & parenteral nutrition calculations
Answer: GIR = 4.58 mg/kg/min
Parenteral nutrition: dextrose provides 3.4 kcal/g, amino acids 4 kcal/g and lipid emulsion the kcal/mL stated (2 kcal/mL for 20%, 1.1 kcal/mL for 10%). Grams = % × mL/100. Non-protein kcal (NPC) = dextrose + lipid kcal; nitrogen = protein/6.25. The glucose infusion rate (GIR) in mg/kg/min = dextrose mg/(kg × minutes). The numbers are for practice only; at the bedside always follow local protocols and have high-risk doses double-checked.
Dextrose concentration
12.5% = 125 mg/mL
Dextrose per minute
125·33/60 = 68.75 mg/min
Per kilogram
GIR = 68.75/15 = 4.583 ≈ 4.58 mg/kg/min
Answer
GIR = 4.58 mg/kg/min
Shortcut: GIR = % dextrose × mL/h/(6 × kg).
3.IV fluids & fluid balance
Answer: U = 1.67 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 + 225 + 400 = 900 mL
Per kilogram per hour
U = 900/(45·12) = 1.667 ≈ 1.67 mL/kg/h
Answer
U = 1.67 mL/kg/h
4.IV fluids & fluid balance
Answer: t = 12.3 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.
First part
125·4 = 500 mL
1000 − 500 = 500 mL left
Second part
500/60 = 8.333 h
Total time
t = 4 + 8.333 = 12.33 ≈ 12.3 h
Answer
t = 12.3 h
That is about 12 h 20 min, so the bag runs out at about 01:20.