Practice exercise (made-up values, not clinical guidance). A 51 kg patient has a fluid goal of 30 mL/kg/day and receives all fluid through a feeding tube. The formula is 81% free water and runs at 50 mL/h for 18 hours a day. The rest of the fluid is given as water flushes every 6 hours. What volume V is each flush? Round to the nearest whole number.
51 kg30 mL/kg/day81%50 mL/h · 18 hevery 6 h
V = mL
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). A 77 kg adult receives 1200 mL of parenteral nutrition containing 20% dextrose, infused over 18 hours. Find the glucose infusion rate GIR in mg/kg/min. Round to two decimal places.
77 kg1200 mLdextrose 20%18 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 IV infusion ran at the rate shown for the whole shift. Find the total intake I in mL. Count ice chips as half their volume.
Practice exercise (made-up values, not clinical guidance). A 500 mL bag runs by pump at 100 mL/h. At 12:30, 300 mL have already been infused. How many hours t until the bag is empty? Round to one decimal place.
500 mL300 mL infused100 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: V = 200 mL
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.
Fluid goal
30·51 = 1530 mL/day
Free water from the formula
50·18 = 900 mL
900·0.81 = 729 mL
Water still needed
1530 − 729 = 801 mL/day
Volume per flush
24/6 = 4 flushes
V = 801/4 = 200.3 ≈ 200 mL
Answer
V = 200 mL
2.Enteral & parenteral nutrition calculations
Answer: GIR = 2.89 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
18·60 = 1080 min
Glucose infusion rate
GIR = 240 000/(77·1080) = 2.886 ≈ 2.89 mg/kg/min
Answer
GIR = 2.89 mg/kg/min
3.IV fluids & fluid balance
Answer: I = 1780 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: 240 + 240 + 200 = 680 mL
ice chips: 200/2 = 100 mL
IV infusion: 100·8 = 800 mL
IV antibiotic: 2·100 = 200 mL
I = 1780 mL
Answer
I = 1780 mL
4.IV fluids & fluid balance
Answer: t = 2 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 − 300 = 200 mL
Time
t = 200/100 = 2 h
Answer
t = 2 h
That is about 2 h 00 min, so the bag runs out at about 14:30.