Practice exercise (made-up values, not clinical guidance). A 70 kg patient needs 1.3 g of protein per kg a day. The tube feed contains 44 g of protein per litre and runs at 70 mL/h for 24 hours a day. How many grams of extra protein ΔP a day are still needed? Round to one decimal place.
70 kg1.3 g/kg/day44 g/L70 mL/h · 24 h
ΔP = g/day
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). Over 24 hours a patient receives 1200 mL of parenteral nutrition with final concentrations of 25% dextrose and 4.25% 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.
1200 mLdextrose 25%amino acids 4.25%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 8-hour shift. The IV infusion ran at the rate shown for the whole shift. Find the total intake I in mL.
milk: 100 mLwater: 240 mLjuice: 120 mLIV infusion: 125 mL/h × 8 hIV antibiotic: 2 × 100 mL
I = mL
4.IV fluids & fluid balanceHard
Practice exercise (made-up values, not clinical guidance). A 1000 mL bag runs by pump at 50 mL/h. At 09:00, 500 mL have already been infused. How many hours t until the bag is empty? Round to one decimal place.
1000 mL500 mL infused50 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: ΔP = 17.1 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
1.3·70 = 91 g/day
Protein from the feed
70·24 = 1680 mL = 1.68 L
1.68·44 = 73.92 g/day
Shortfall
ΔP = 91 − 73.92 = 17.08 ≈ 17.1 g/day
Answer
ΔP = 17.1 g/day
2.Enteral & parenteral nutrition calculations
Answer: NPC : N = 150
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: 25·1200/100 = 300 g
amino acids: 4.25·1200/100 = 51 g
Kilocalories per component
dextrose: 300·3.4 = 1020 kcal
amino acids: 51·4 = 204 kcal
lipid: 100·2 = 200 kcal
Non-protein kcal and nitrogen
NPC = 1020 + 200 = 1220 kcal
N = 51/6.25 = 8.16 g
Ratio
NPC : N = 1220/8.16 = 149.5 ≈ 150 : 1
Answer
NPC : N = 150
Ratios of about 150 : 1 are typical for stable patients; lower ratios give relatively more protein.
3.IV fluids & fluid balance
Answer: I = 1660 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.
Add the intake
oral: 100 + 240 + 120 = 460 mL
IV infusion: 125·8 = 1000 mL
IV antibiotic: 2·100 = 200 mL
I = 1660 mL
Answer
I = 1660 mL
4.IV fluids & fluid balance
Answer: t = 10 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 − 500 = 500 mL
Time
t = 500/50 = 10 h
Answer
t = 10 h
That is about 10 h 00 min, so the bag runs out at about 19:00.