Practice exercise (made-up values, not clinical guidance). A 60 kg patient needs 1.8 g of protein per kg a day. The tube feed contains 68 g of protein per litre and runs at 60 mL/h for 16 hours a day. How many grams of extra protein ΔP a day are still needed? Round to one decimal place.
60 kg1.8 g/kg/day68 g/L60 mL/h · 16 h
ΔP = g/day
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). A child who weighs 10 kg receives 10% dextrose at 51 mL/h. Find the glucose infusion rate GIR in mg/kg/min. Round to two decimal places.
10 kg10%51 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 8-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).
Practice exercise (made-up values, not clinical guidance). A 1000 mL bag runs by pump at 150 mL/h. At 21:00, 400 mL have already been infused. How many hours t until the bag is empty? Round to one decimal place.
1000 mL400 mL infused150 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: ΔP = 42.7 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
1.8·60 = 108 g/day
Protein from the feed
60·16 = 960 mL = 0.96 L
0.96·68 = 65.28 g/day
Shortfall
ΔP = 108 − 65.28 = 42.72 ≈ 42.7 g/day
Answer
ΔP = 42.7 g/day
2.Enteral & parenteral nutrition calculations
Answer: GIR = 8.5 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
10% = 100 mg/mL
Dextrose per minute
100·51/60 = 85 mg/min
Per kilogram
GIR = 85/10 = 8.5 mg/kg/min
Answer
GIR = 8.5 mg/kg/min
Shortcut: GIR = % dextrose × mL/h/(6 × kg).
3.IV fluids & fluid balance
Answer: B = −630 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: 180 + 200 = 380 mL
IV infusion: 50·8 = 400 mL
IV antibiotic: 1·100 = 100 mL
total intake = 880 mL
Total output
350 + 225 + 500 + 325 + 110 = 1510 mL
Balance
B = 880 − 1510 = −630 mL
Answer
B = −630 mL
Negative: the patient lost more fluid than went in.
4.IV fluids & fluid balance
Answer: t = 4 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 − 400 = 600 mL
Time
t = 600/150 = 4 h
Answer
t = 4 h
That is about 4 h 00 min, so the bag runs out at about 01:00.