Practice exercise (made-up values, not clinical guidance). A 79 kg patient needs 1.3 g of protein per kg a day. The tube feed contains 55 g of protein per litre and runs at 40 mL/h for 24 hours a day. A protein powder supplies 10 g of protein per scoop. How many scoops n a day are needed to cover the shortfall? Round up to a whole scoop.
79 kg1.3 g/kg/day55 g/L40 mL/h · 24 h10 g/scoop
n =
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). Over 24 hours a patient receives 1000 mL of parenteral nutrition with final concentrations of 20% dextrose and 4% amino acids, plus 250 mL of 20% lipid emulsion (2 kcal/mL). Find the non-protein energy NPC in kcal per day. Round to the nearest whole number.
1000 mLdextrose 20%amino acids 4%lipid 250 mL · 2 kcal/mL
NPC = kcal/day
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 500 mL bag runs by pump at 50 mL/h. At 16:00, 100 mL have already been infused. How many hours t until the bag is empty? Round to one decimal place.
500 mL100 mL infused50 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: n = 5
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
1.3·79 = 102.7 g/day
Protein from the feed
40·24 = 960 mL = 0.96 L
0.96·55 = 52.8 g/day
Shortfall
ΔP = 102.7 − 52.8 = 49.9 g
Scoops
49.9/10 = 4.99 → n = 5
Answer
n = 5
2.Enteral & parenteral nutrition calculations
Answer: NPC = 1180 kcal/day
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.
Grams of dextrose and amino acids
dextrose: 20·1000/100 = 200 g
amino acids: 4·1000/100 = 40 g
Kilocalories per component
dextrose: 200·3.4 = 680 kcal
amino acids: 40·4 = 160 kcal
lipid: 250·2 = 500 kcal
Non-protein energy
NPC = 680 + 500 = 1180 kcal/day
Answer
NPC = 1180 kcal/day
3.IV fluids & fluid balance
Answer: B = 815 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 + 120 + 240 = 540 mL
IV infusion: 125·8 = 1000 mL
IV antibiotic: 1·100 = 100 mL
total intake = 1640 mL
Total output
450 + 325 + 50 = 825 mL
Balance
B = 1640 − 825 = 815 mL
Answer
B = 815 mL
Positive: more fluid went in than came out.
4.IV fluids & fluid balance
Answer: t = 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 − 100 = 400 mL
Time
t = 400/50 = 8 h
Answer
t = 8 h
That is about 8 h 00 min, so the bag runs out at about 00:00.