Practice exercise (made-up values, not clinical guidance). A 60 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 70 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.
60 kg30 mL/kg/day70%70 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 13 kg receives 10% dextrose at 30 mL/h. Find the glucose infusion rate GIR in mg/kg/min. Round to two decimal places.
13 kg10%30 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 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 500 mL infusion starts at 07:00 at 120 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.
500 mL120 mL/h · 3 h100 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: V = 205 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
30·60 = 1800 mL/day
Free water from the formula
70·20 = 1400 mL
1400·0.7 = 980 mL
Water still needed
1800 − 980 = 820 mL/day
Volume per flush
24/6 = 4 flushes
V = 820/4 = 205 mL
Answer
V = 205 mL
2.Enteral & parenteral nutrition calculations
Answer: GIR = 3.85 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
10% = 100 mg/mL
Dextrose per minute
100·30/60 = 50 mg/min
Per kilogram
GIR = 50/13 = 3.846 ≈ 3.85 mg/kg/min
Answer
GIR = 3.85 mg/kg/min
Shortcut: GIR = % dextrose × mL/h/(6 × kg).
3.IV fluids & fluid balance
Answer: B = −130 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: 200 + 240 + 180 = 620 mL
IV infusion: 50·12 = 600 mL
IV antibiotic: 1·50 = 50 mL
total intake = 1270 mL
Total output
350 + 300 + 325 + 425 = 1400 mL
Balance
B = 1270 − 1400 = −130 mL
Answer
B = −130 mL
Negative: the patient lost more fluid than went in.
4.IV fluids & fluid balance
Answer: t = 4.4 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
120·3 = 360 mL
500 − 360 = 140 mL left
Second part
140/100 = 1.4 h
Total time
t = 3 + 1.4 = 4.4 h
Answer
t = 4.4 h
That is about 4 h 24 min, so the bag runs out at about 11:24.