Practice exercise (made-up values, not clinical guidance). A 69 kg patient needs 1.8 g of protein per kg a day. The tube feed contains 84 g of protein per litre and runs at 60 mL/h for 20 hours a day. A protein powder supplies 7 g of protein per scoop. How many scoops n a day are needed to cover the shortfall? Round up to a whole scoop.
69 kg1.8 g/kg/day84 g/L60 mL/h · 20 h7 g/scoop
n =
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). Over 24 hours a patient receives 1500 mL of parenteral nutrition with final concentrations of 12.5% dextrose and 6% amino acids, plus 250 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.
1500 mLdextrose 12.5%amino acids 6%lipid 250 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 8-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 bag runs by pump at 75 mL/h. At 06:00, 350 mL have already been infused. How many hours t until the bag is empty? Round to one decimal place.
1000 mL350 mL infused75 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: n = 4
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
1.8·69 = 124.2 g/day
Protein from the feed
60·20 = 1200 mL = 1.2 L
1.2·84 = 100.8 g/day
Shortfall
ΔP = 124.2 − 100.8 = 23.4 g
Scoops
23.4/7 = 3.343 → n = 4
Answer
n = 4
2.Enteral & parenteral nutrition calculations
Answer: NPC : N = 63
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: 12.5·1500/100 = 187.5 g
amino acids: 6·1500/100 = 90 g
Kilocalories per component
dextrose: 187.5·3.4 = 637.5 kcal
amino acids: 90·4 = 360 kcal
lipid: 250·1.1 = 275 kcal
Non-protein kcal and nitrogen
NPC = 637.5 + 275 = 912.5 kcal
N = 90/6.25 = 14.4 g
Ratio
NPC : N = 912.5/14.4 = 63.37 ≈ 63 : 1
Answer
NPC : N = 63
Ratios of about 150 : 1 are typical for stable patients; lower ratios give relatively more protein.
3.IV fluids & fluid balance
Answer: B = −855 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 + 180 = 420 mL
IV infusion: 50·8 = 400 mL
IV antibiotic: 1·50 = 50 mL
total intake = 870 mL
Total output
400 + 425 + 400 + 500 = 1725 mL
Balance
B = 870 − 1725 = −855 mL
Answer
B = −855 mL
Negative: the patient lost more fluid than went in.
4.IV fluids & fluid balance
Answer: t = 8.7 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 − 350 = 650 mL
Time
t = 650/75 = 8.667 ≈ 8.7 h
Answer
t = 8.7 h
That is about 8 h 40 min, so the bag runs out at about 14:40.