Practice exercise (made-up values, not clinical guidance). A 73 kg patient needs 1.5 g of protein per kg a day. The tube feed contains 44 g of protein per litre and runs at 80 mL/h for 24 hours a day. A protein powder supplies 5 g of protein per scoop. How many scoops n a day are needed to cover the shortfall? Round up to a whole scoop.
73 kg1.5 g/kg/day44 g/L80 mL/h · 24 h5 g/scoop
n =
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 17.5% dextrose and 4% amino acids, plus 100 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 17.5%amino acids 4%lipid 100 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 74 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 1000 mL bag runs by pump at 50 mL/h. At 17:00, 650 mL have already been infused. How many hours t until the bag is empty? Round to one decimal place.
1000 mL650 mL infused50 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: n = 6
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
1.5·73 = 109.5 g/day
Protein from the feed
80·24 = 1920 mL = 1.92 L
1.92·44 = 84.48 g/day
Shortfall
ΔP = 109.5 − 84.48 = 25.02 g
Scoops
25.02/5 = 5.004 → n = 6
Answer
n = 6
2.Enteral & parenteral nutrition calculations
Answer: NPC : N = 106
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: 17.5·2400/100 = 420 g
amino acids: 4·2400/100 = 96 g
Kilocalories per component
dextrose: 420·3.4 = 1428 kcal
amino acids: 96·4 = 384 kcal
lipid: 100·2 = 200 kcal
Non-protein kcal and nitrogen
NPC = 1428 + 200 = 1628 kcal
N = 96/6.25 = 15.36 g
Ratio
NPC : N = 1628/15.36 = 106 : 1
Answer
NPC : N = 106
Ratios of about 150 : 1 are typical for stable patients; lower ratios give relatively more protein.
3.IV fluids & fluid balance
Answer: U = 1.35 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
500 + 425 + 275 = 1200 mL
Per kilogram per hour
U = 1200/(74·12) = 1.351 ≈ 1.35 mL/kg/h
Answer
U = 1.35 mL/kg/h
4.IV fluids & fluid balance
Answer: t = 7 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 − 650 = 350 mL
Time
t = 350/50 = 7 h
Answer
t = 7 h
That is about 7 h 00 min, so the bag runs out at about 00:00.