Practice exercise (made-up values, not clinical guidance). A 76 kg patient needs 1.2 g of protein per kg a day. The tube feed contains 40 g of protein per litre and runs at 70 mL/h for 16 hours a day. How many grams of extra protein ΔP a day are still needed? Round to one decimal place.
76 kg1.2 g/kg/day40 g/L70 mL/h · 16 h
ΔP = g/day
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). A child who weighs 14 kg receives 7.5% dextrose at 50 mL/h. Find the glucose infusion rate GIR in mg/kg/min. Round to two decimal places.
14 kg7.5%50 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 IV infusion ran at the rate shown for the whole shift. Find the total intake I in mL.
tea: 240 mLjuice: 120 mLmilk: 100 mLIV infusion: 50 mL/h × 12 hIV antibiotic: 1 × 100 mL
I = mL
4.IV fluids & fluid balanceHard
Practice exercise (made-up values, not clinical guidance). A 500 mL bag runs by pump at 80 mL/h. At 10:30, 200 mL have already been infused. How many hours t until the bag is empty? Round to one decimal place.
500 mL200 mL infused80 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: ΔP = 46.4 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
1.2·76 = 91.2 g/day
Protein from the feed
70·16 = 1120 mL = 1.12 L
1.12·40 = 44.8 g/day
Shortfall
ΔP = 91.2 − 44.8 = 46.4 g/day
Answer
ΔP = 46.4 g/day
2.Enteral & parenteral nutrition calculations
Answer: GIR = 4.46 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
7.5% = 75 mg/mL
Dextrose per minute
75·50/60 = 62.5 mg/min
Per kilogram
GIR = 62.5/14 = 4.464 ≈ 4.46 mg/kg/min
Answer
GIR = 4.46 mg/kg/min
Shortcut: GIR = % dextrose × mL/h/(6 × kg).
3.IV fluids & fluid balance
Answer: I = 1160 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.
Add the intake
oral: 240 + 120 + 100 = 460 mL
IV infusion: 50·12 = 600 mL
IV antibiotic: 1·100 = 100 mL
I = 1160 mL
Answer
I = 1160 mL
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.
Volume left
500 − 200 = 300 mL
Time
t = 300/80 = 3.75 ≈ 3.8 h
Answer
t = 3.8 h
That is about 3 h 45 min, so the bag runs out at about 14:15.