Practice exercise (made-up values, not clinical guidance). An 81 kg patient needs 1.5 g of protein per kg a day. The tube feed contains 55 g of protein per litre and runs at 85 mL/h for 18 hours a day. How many grams of extra protein ΔP a day are still needed? Round to one decimal place.
81 kg1.5 g/kg/day55 g/L85 mL/h · 18 h
ΔP = g/day
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). A 73 kg adult receives 1200 mL of parenteral nutrition containing 20% dextrose, infused over 12 hours. Find the glucose infusion rate GIR in mg/kg/min. Round to two decimal places.
73 kg1200 mLdextrose 20%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 8-hour shift. The patient weighs 45 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 infusion starts at 18:00 at 80 mL/h. After 2 hours the rate is changed to 150 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 mL80 mL/h · 2 h150 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: ΔP = 37.4 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
1.5·81 = 121.5 g/day
Protein from the feed
85·18 = 1530 mL = 1.53 L
1.53·55 = 84.15 g/day
Shortfall
ΔP = 121.5 − 84.15 = 37.35 ≈ 37.4 g/day
Answer
ΔP = 37.4 g/day
2.Enteral & parenteral nutrition calculations
Answer: GIR = 4.57 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
20·1200/100 = 240 g = 240 000 mg
Minutes of infusion
12·60 = 720 min
Glucose infusion rate
GIR = 240 000/(73·720) = 4.566 ≈ 4.57 mg/kg/min
Answer
GIR = 4.57 mg/kg/min
3.IV fluids & fluid balance
Answer: U = 1.53 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
400 + 150 = 550 mL
Per kilogram per hour
U = 550/(45·8) = 1.528 ≈ 1.53 mL/kg/h
Answer
U = 1.53 mL/kg/h
4.IV fluids & fluid balance
Answer: t = 7.6 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
80·2 = 160 mL
1000 − 160 = 840 mL left
Second part
840/150 = 5.6 h
Total time
t = 2 + 5.6 = 7.6 h
Answer
t = 7.6 h
That is about 7 h 36 min, so the bag runs out at about 01:36.