Practice exercise (made-up values, not clinical guidance). A 50 kg patient has a fluid goal of 30 mL/kg/day and receives all fluid through a feeding tube. The formula is 76% free water and runs at 75 mL/h for 20 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.
50 kg30 mL/kg/day76%75 mL/h · 20 hevery 6 h
V = mL
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). A child who weighs 15 kg receives 7.5% dextrose at 57 mL/h. Find the glucose infusion rate GIR in mg/kg/min. Round to two decimal places.
15 kg7.5%57 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 total intake I in mL. Count ice chips as half their volume.
Practice exercise (made-up values, not clinical guidance). A 500 mL bag was started at 06:00 and runs by pump at 50 mL/h. How many mL V are left in the bag at 08:00?
500 mL50 mL/h06:00 → 08:00
V = mL
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: V = 90 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
30·50 = 1500 mL/day
Free water from the formula
75·20 = 1500 mL
1500·0.76 = 1140 mL
Water still needed
1500 − 1140 = 360 mL/day
Volume per flush
24/6 = 4 flushes
V = 360/4 = 90 mL
Answer
V = 90 mL
2.Enteral & parenteral nutrition calculations
Answer: GIR = 4.75 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
7.5% = 75 mg/mL
Dextrose per minute
75·57/60 = 71.25 mg/min
Per kilogram
GIR = 71.25/15 = 4.75 mg/kg/min
Answer
GIR = 4.75 mg/kg/min
Shortcut: GIR = % dextrose × mL/h/(6 × kg).
3.IV fluids & fluid balance
Answer: I = 1000 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: 120 + 120 + 200 = 440 mL
ice chips: 120/2 = 60 mL
IV infusion: 50·8 = 400 mL
IV antibiotic: 1·100 = 100 mL
I = 1000 mL
Answer
I = 1000 mL
4.IV fluids & fluid balance
Answer: V = 400 mL
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.