Practice exercise (made-up values, not clinical guidance). A 90 kg patient needs 1.5 g of protein per kg a day. The tube feed contains 68 g of protein per litre and runs at 90 mL/h for 18 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.
90 kg1.5 g/kg/day68 g/L90 mL/h · 18 h5 g/scoop
n =
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). A 51 kg adult receives 1200 mL of parenteral nutrition containing 12.5% dextrose, infused over 12 hours. Find the glucose infusion rate GIR in mg/kg/min. Round to two decimal places.
51 kg1200 mLdextrose 12.5%12 h
GIR = mg/kg/min
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 500 mL bag runs by pump at 50 mL/h. At 11:00, 50 mL have already been infused. How many hours t until the bag is empty? Round to one decimal place.
500 mL50 mL infused50 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: n = 5
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
1.5·90 = 135 g/day
Protein from the feed
90·18 = 1620 mL = 1.62 L
1.62·68 = 110.2 g/day
Shortfall
ΔP = 135 − 110.2 = 24.84 g
Scoops
24.84/5 = 4.968 → n = 5
Answer
n = 5
2.Enteral & parenteral nutrition calculations
Answer: GIR = 4.08 mg/kg/min
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.
Dextrose in the bag
12.5·1200/100 = 150 g = 150 000 mg
Minutes of infusion
12·60 = 720 min
Glucose infusion rate
GIR = 150 000/(51·720) = 4.085 ≈ 4.08 mg/kg/min
Answer
GIR = 4.08 mg/kg/min
3.IV fluids & fluid balance
Answer: B = 20 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: 60·12 = 720 mL
IV antibiotic: 1·100 = 100 mL
total intake = 1160 mL
Total output
275 + 400 + 375 + 90 = 1140 mL
Balance
B = 1160 − 1140 = 20 mL
Answer
B = 20 mL
Positive: more fluid went in than came out.
4.IV fluids & fluid balance
Answer: t = 9 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 = 450/50 = 9 h
Answer
t = 9 h
That is about 9 h 00 min, so the bag runs out at about 20:00.