Practice exercise (made-up values, not clinical guidance). A 61 kg patient has a fluid goal of 35 mL/kg/day and receives all fluid through a feeding tube. The formula is 81% free water and runs at 80 mL/h for 20 hours a day. The rest of the fluid is given as water flushes every 4 hours. What volume V is each flush? Round to the nearest whole number.
61 kg35 mL/kg/day81%80 mL/h · 20 hevery 4 h
V = mL
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). A child who weighs 17.5 kg receives 12.5% dextrose at 33 mL/h. Find the glucose infusion rate GIR in mg/kg/min. Round to two decimal places.
17.5 kg12.5%33 mL/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 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 50 mL/h. At 21:00, 650 mL have already been infused. How many hours t until the bag is empty? Round to one decimal place.
1000 mL650 mL infused50 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: V = 140 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
35·61 = 2135 mL/day
Free water from the formula
80·20 = 1600 mL
1600·0.81 = 1296 mL
Water still needed
2135 − 1296 = 839 mL/day
Volume per flush
24/4 = 6 flushes
V = 839/6 = 139.8 ≈ 140 mL
Answer
V = 140 mL
2.Enteral & parenteral nutrition calculations
Answer: GIR = 3.93 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 concentration
12.5% = 125 mg/mL
Dextrose per minute
125·33/60 = 68.75 mg/min
Per kilogram
GIR = 68.75/17.5 = 3.929 ≈ 3.93 mg/kg/min
Answer
GIR = 3.93 mg/kg/min
Shortcut: GIR = % dextrose × mL/h/(6 × kg).
3.IV fluids & fluid balance
Answer: B = −500 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: 250 + 100 = 350 mL
IV infusion: 50·8 = 400 mL
IV antibiotic: 2·100 = 200 mL
total intake = 950 mL
Total output
150 + 425 + 450 + 275 + 150 = 1450 mL
Balance
B = 950 − 1450 = −500 mL
Answer
B = −500 mL
Negative: the patient lost more fluid than went in.
4.IV fluids & fluid balance
Answer: t = 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 − 650 = 350 mL
Time
t = 350/50 = 7 h
Answer
t = 7 h
That is about 7 h 00 min, so the bag runs out at about 04:00.