Practice exercise (made-up values, not clinical guidance). A 63 kg patient needs 1.8 g of protein per kg a day. The tube feed contains 40 g of protein per litre and runs at 80 mL/h for 20 hours a day. How many grams of extra protein ΔP a day are still needed? Round to one decimal place.
63 kg1.8 g/kg/day40 g/L80 mL/h · 20 h
ΔP = g/day
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). Over 24 hours a patient receives 2400 mL of parenteral nutrition with final concentrations of 10% dextrose and 3.5% amino acids, plus 250 mL of 20% lipid emulsion (2 kcal/mL). Find the non-protein kilocalorie to nitrogen ratio NPC : N (the number x in x : 1). Round to the nearest whole number.
2400 mLdextrose 10%amino acids 3.5%lipid 250 mL · 2 kcal/mL
NPC : N =
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 56 kg. Find the average urine output U in mL/kg/h. Round to two decimal places.
56 kg12 hurine: 375 mLurine: 425 mLwound drain: 70 mL
U = mL/kg/h
4.IV fluids & fluid balanceHard
Practice exercise (made-up values, not clinical guidance). A 500 mL bag runs by pump at 75 mL/h. At 10:00, 100 mL have already been infused. How many hours t until the bag is empty? Round to one decimal place.
500 mL100 mL infused75 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: ΔP = 49.4 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
1.8·63 = 113.4 g/day
Protein from the feed
80·20 = 1600 mL = 1.6 L
1.6·40 = 64 g/day
Shortfall
ΔP = 113.4 − 64 = 49.4 g/day
Answer
ΔP = 49.4 g/day
2.Enteral & parenteral nutrition calculations
Answer: NPC : N = 98
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: 10·2400/100 = 240 g
amino acids: 3.5·2400/100 = 84 g
Kilocalories per component
dextrose: 240·3.4 = 816 kcal
amino acids: 84·4 = 336 kcal
lipid: 250·2 = 500 kcal
Non-protein kcal and nitrogen
NPC = 816 + 500 = 1316 kcal
N = 84/6.25 = 13.44 g
Ratio
NPC : N = 1316/13.44 = 97.92 ≈ 98 : 1
Answer
NPC : N = 98
Ratios of about 150 : 1 are typical for stable patients; lower ratios give relatively more protein.
3.IV fluids & fluid balance
Answer: U = 1.19 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
375 + 425 = 800 mL
Per kilogram per hour
U = 800/(56·12) = 1.19 mL/kg/h
Answer
U = 1.19 mL/kg/h
4.IV fluids & fluid balance
Answer: t = 5.3 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.
Volume left
500 − 100 = 400 mL
Time
t = 400/75 = 5.333 ≈ 5.3 h
Answer
t = 5.3 h
That is about 5 h 20 min, so the bag runs out at about 15:20.