Practice exercise (made-up values, not clinical guidance). A 94 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 90 mL/h for 24 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.
94 kg30 mL/kg/day76%90 mL/h · 24 hevery 6 h
V = mL
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). A 51 kg adult receives 1800 mL of parenteral nutrition containing 20% dextrose, infused over 24 hours. Find the glucose infusion rate GIR in mg/kg/min. Round to two decimal places.
51 kg1800 mLdextrose 20%24 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 500 mL infusion starts at 08:00 at 125 mL/h. After 3 hours the rate is changed to 75 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 mL125 mL/h · 3 h75 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: V = 295 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
30·94 = 2820 mL/day
Free water from the formula
90·24 = 2160 mL
2160·0.76 = 1642 mL
Water still needed
2820 − 1642 = 1178 mL/day
Volume per flush
24/6 = 4 flushes
V = 1178/4 = 294.6 ≈ 295 mL
Answer
V = 295 mL
2.Enteral & parenteral nutrition calculations
Answer: GIR = 4.9 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
20·1800/100 = 360 g = 360 000 mg
Minutes of infusion
24·60 = 1440 min
Glucose infusion rate
GIR = 360 000/(51·1440) = 4.902 ≈ 4.9 mg/kg/min
Answer
GIR = 4.9 mg/kg/min
3.IV fluids & fluid balance
Answer: B = 450 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 + 200 + 120 = 520 mL
IV infusion: 125·8 = 1000 mL
IV antibiotic: 1·50 = 50 mL
total intake = 1570 mL
Total output
150 + 225 + 500 + 175 + 70 = 1120 mL
Balance
B = 1570 − 1120 = 450 mL
Answer
B = 450 mL
Positive: more fluid went in than came out.
4.IV fluids & fluid balance
Answer: t = 4.7 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.
First part
125·3 = 375 mL
500 − 375 = 125 mL left
Second part
125/75 = 1.667 h
Total time
t = 3 + 1.667 = 4.667 ≈ 4.7 h
Answer
t = 4.7 h
That is about 4 h 40 min, so the bag runs out at about 12:40.