Practice exercise (made-up values, not clinical guidance). A 51 kg patient needs 2 g of protein per kg a day. The tube feed contains 84 g of protein per litre and runs at 40 mL/h for 16 hours a day. How many grams of extra protein ΔP a day are still needed? Round to one decimal place.
51 kg2 g/kg/day84 g/L40 mL/h · 16 h
ΔP = g/day
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 25% dextrose and 5% amino acids, plus 500 mL of 10% lipid emulsion (1.1 kcal/mL). Find the non-protein kilocalorie to nitrogen ratio NPC : N (the number x in x : 1). Round to the nearest whole number.
1000 mLdextrose 25%amino acids 5%lipid 500 mL · 1.1 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 86 kg. Find the average urine output U in mL/kg/h. Round to two decimal places.
Practice exercise (made-up values, not clinical guidance). A 500 mL bag runs by pump at 75 mL/h. At 16:30, 50 mL have already been infused. How many hours t until the bag is empty? Round to one decimal place.
500 mL50 mL infused75 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: ΔP = 48.2 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
2·51 = 102 g/day
Protein from the feed
40·16 = 640 mL = 0.64 L
0.64·84 = 53.76 g/day
Shortfall
ΔP = 102 − 53.76 = 48.24 ≈ 48.2 g/day
Answer
ΔP = 48.2 g/day
2.Enteral & parenteral nutrition calculations
Answer: NPC : N = 175
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: 25·1000/100 = 250 g
amino acids: 5·1000/100 = 50 g
Kilocalories per component
dextrose: 250·3.4 = 850 kcal
amino acids: 50·4 = 200 kcal
lipid: 500·1.1 = 550 kcal
Non-protein kcal and nitrogen
NPC = 850 + 550 = 1400 kcal
N = 50/6.25 = 8 g
Ratio
NPC : N = 1400/8 = 175 : 1
Answer
NPC : N = 175
Ratios of about 150 : 1 are typical for stable patients; lower ratios give relatively more protein.
3.IV fluids & fluid balance
Answer: U = 0.87 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
225 + 475 + 200 = 900 mL
Per kilogram per hour
U = 900/(86·12) = 0.8721 ≈ 0.87 mL/kg/h
Answer
U = 0.87 mL/kg/h
4.IV fluids & fluid balance
Answer: t = 6 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 − 50 = 450 mL
Time
t = 450/75 = 6 h
Answer
t = 6 h
That is about 6 h 00 min, so the bag runs out at about 22:30.