Practice exercise (made-up values, not clinical guidance). A 66 kg patient needs 1.3 g of protein per kg a day. The tube feed contains 40 g of protein per litre and runs at 40 mL/h for 20 hours a day. How many grams of extra protein ΔP a day are still needed? Round to one decimal place.
66 kg1.3 g/kg/day40 g/L40 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 25% dextrose and 5% amino acids, plus 500 mL of 20% lipid emulsion (2 kcal/mL). Find the total energy E the patient receives in kcal per day. Round to the nearest whole number.
2400 mLdextrose 25%amino acids 5%lipid 500 mL · 2 kcal/mL
E = 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 12-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 1000 mL infusion starts at 10:30 at 120 mL/h. After 4 hours the rate is changed to 80 mL/h and is not changed again. How many hours t after the start will the bag be empty? Round to one decimal place.
1000 mL120 mL/h · 4 h80 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: ΔP = 53.8 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
1.3·66 = 85.8 g/day
Protein from the feed
40·20 = 800 mL = 0.8 L
0.8·40 = 32 g/day
Shortfall
ΔP = 85.8 − 32 = 53.8 g/day
Answer
ΔP = 53.8 g/day
2.Enteral & parenteral nutrition calculations
Answer: E = 3520 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: 25·2400/100 = 600 g
amino acids: 5·2400/100 = 120 g
Kilocalories per component
dextrose: 600·3.4 = 2040 kcal
amino acids: 120·4 = 480 kcal
lipid: 500·2 = 1000 kcal
Total energy
E = 2040 + 480 + 1000 = 3520 kcal/day
Answer
E = 3520 kcal/day
3.IV fluids & fluid balance
Answer: B = 1160 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: 240 + 100 = 340 mL
IV infusion: 125·12 = 1500 mL
IV antibiotic: 2·100 = 200 mL
total intake = 2040 mL
Total output
400 + 250 + 30 + 200 = 880 mL
Balance
B = 2040 − 880 = 1160 mL
Answer
B = 1160 mL
Positive: more fluid went in than came out.
4.IV fluids & fluid balance
Answer: t = 10.5 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.
First part
120·4 = 480 mL
1000 − 480 = 520 mL left
Second part
520/80 = 6.5 h
Total time
t = 4 + 6.5 = 10.5 h
Answer
t = 10.5 h
That is about 10 h 30 min, so the bag runs out at about 21:00.