Practice exercise (made-up values, not clinical guidance). A 50 kg patient needs 1.3 g of protein per kg a day. The tube feed contains 44 g of protein per litre and runs at 45 mL/h for 20 hours a day. How many grams of extra protein ΔP a day are still needed? Round to one decimal place.
50 kg1.3 g/kg/day44 g/L45 mL/h · 20 h
ΔP = g/day
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). A 77 kg adult receives 1200 mL of parenteral nutrition containing 12.5% dextrose, infused over 12 hours. Find the glucose infusion rate GIR in mg/kg/min. Round to two decimal places.
77 kg1200 mLdextrose 12.5%12 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 52 kg. Find the average urine output U in mL/kg/h. Round to two decimal places.
52 kg12 hurine: 475 mLurine: 275 mLwound drain: 100 mL
U = mL/kg/h
4.IV fluids & fluid balanceHard
Practice exercise (made-up values, not clinical guidance). A 500 mL infusion starts at 18:30 at 125 mL/h. After 3 hours the rate is changed to 150 mL/h and is not changed again. How many hours t after the start will the bag be empty? Round to one decimal place.
500 mL125 mL/h · 3 h150 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: ΔP = 25.4 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
1.3·50 = 65 g/day
Protein from the feed
45·20 = 900 mL = 0.9 L
0.9·44 = 39.6 g/day
Shortfall
ΔP = 65 − 39.6 = 25.4 g/day
Answer
ΔP = 25.4 g/day
2.Enteral & parenteral nutrition calculations
Answer: GIR = 2.71 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 in the bag
12.5·1200/100 = 150 g = 150 000 mg
Minutes of infusion
12·60 = 720 min
Glucose infusion rate
GIR = 150 000/(77·720) = 2.706 ≈ 2.71 mg/kg/min
Answer
GIR = 2.71 mg/kg/min
3.IV fluids & fluid balance
Answer: U = 1.2 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
475 + 275 = 750 mL
Per kilogram per hour
U = 750/(52·12) = 1.202 ≈ 1.2 mL/kg/h
Answer
U = 1.2 mL/kg/h
4.IV fluids & fluid balance
Answer: t = 3.8 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
125·3 = 375 mL
500 − 375 = 125 mL left
Second part
125/150 = 0.8333 h
Total time
t = 3 + 0.8333 = 3.833 ≈ 3.8 h
Answer
t = 3.8 h
That is about 3 h 50 min, so the bag runs out at about 22:20.