Practice exercise (made-up values, not clinical guidance). A 72 kg patient has a fluid goal of 35 mL/kg/day and receives all fluid through a feeding tube. The formula is 76% free water and runs at 60 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.
72 kg35 mL/kg/day76%60 mL/h · 20 hevery 4 h
V = mL
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). A 109 kg adult receives 2400 mL of parenteral nutrition containing 17.5% dextrose, infused over 18 hours. Find the glucose infusion rate GIR in mg/kg/min. Round to two decimal places.
109 kg2400 mLdextrose 17.5%18 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 1000 mL infusion starts at 12:30 at 75 mL/h. After 4 hours the rate is changed to 50 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 mL75 mL/h · 4 h50 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: V = 268 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
35·72 = 2520 mL/day
Free water from the formula
60·20 = 1200 mL
1200·0.76 = 912 mL
Water still needed
2520 − 912 = 1608 mL/day
Volume per flush
24/4 = 6 flushes
V = 1608/6 = 268 mL
Answer
V = 268 mL
2.Enteral & parenteral nutrition calculations
Answer: GIR = 3.57 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
17.5·2400/100 = 420 g = 420 000 mg
Minutes of infusion
18·60 = 1080 min
Glucose infusion rate
GIR = 420 000/(109·1080) = 3.568 ≈ 3.57 mg/kg/min
Answer
GIR = 3.57 mg/kg/min
3.IV fluids & fluid balance
Answer: B = 170 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: 240 + 120 = 360 mL
IV infusion: 80·12 = 960 mL
IV antibiotic: 1·100 = 100 mL
total intake = 1420 mL
Total output
150 + 175 + 400 + 325 + 50 + 150 = 1250 mL
Balance
B = 1420 − 1250 = 170 mL
Answer
B = 170 mL
Positive: more fluid went in than came out.
4.IV fluids & fluid balance
Answer: t = 18 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
75·4 = 300 mL
1000 − 300 = 700 mL left
Second part
700/50 = 14 h
Total time
t = 4 + 14 = 18 h
Answer
t = 18 h
That is about 18 h 00 min, so the bag runs out at about 06:30.