Practice exercise (made-up values, not clinical guidance). An 88 kg patient has a fluid goal of 30 mL/kg/day and receives all fluid through a feeding tube. The formula is 70% free water and runs at 75 mL/h for 18 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.
88 kg30 mL/kg/day70%75 mL/h · 18 hevery 4 h
V = mL
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). A child who weighs 6 kg receives 5% dextrose at 26 mL/h. Find the glucose infusion rate GIR in mg/kg/min. Round to two decimal places.
6 kg5%26 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 12-hour shift. The patient weighs 102 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 12:30 at 150 mL/h. After 3 hours the rate is changed to 100 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 mL150 mL/h · 3 h100 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: V = 283 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
30·88 = 2640 mL/day
Free water from the formula
75·18 = 1350 mL
1350·0.7 = 945 mL
Water still needed
2640 − 945 = 1695 mL/day
Volume per flush
24/4 = 6 flushes
V = 1695/6 = 282.5 ≈ 283 mL
Answer
V = 283 mL
2.Enteral & parenteral nutrition calculations
Answer: GIR = 3.61 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
5% = 50 mg/mL
Dextrose per minute
50·26/60 = 21.67 mg/min
Per kilogram
GIR = 21.67/6 = 3.611 ≈ 3.61 mg/kg/min
Answer
GIR = 3.61 mg/kg/min
Shortcut: GIR = % dextrose × mL/h/(6 × kg).
3.IV fluids & fluid balance
Answer: U = 1 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
275 + 275 + 225 + 450 = 1225 mL
Per kilogram per hour
U = 1225/(102·12) = 1.001 ≈ 1 mL/kg/h
Answer
U = 1 mL/kg/h
4.IV fluids & fluid balance
Answer: t = 8.5 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
150·3 = 450 mL
1000 − 450 = 550 mL left
Second part
550/100 = 5.5 h
Total time
t = 3 + 5.5 = 8.5 h
Answer
t = 8.5 h
That is about 8 h 30 min, so the bag runs out at about 21:00.