Practice exercise (made-up values, not clinical guidance). A 62 kg patient has a fluid goal of 35 mL/kg/day and receives all fluid through a feeding tube. The formula is 84% free water and runs at 45 mL/h for 24 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.
62 kg35 mL/kg/day84%45 mL/h · 24 hevery 4 h
V = mL
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). A 45 kg adult receives 1000 mL of parenteral nutrition containing 17.5% dextrose, infused over 24 hours. Find the glucose infusion rate GIR in mg/kg/min. Round to two decimal places.
45 kg1000 mLdextrose 17.5%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 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). Count ice chips as half their volume.
Practice exercise (made-up values, not clinical guidance). A 1000 mL bag runs by pump at 75 mL/h. At 14:30, 200 mL have already been infused. How many hours t until the bag is empty? Round to one decimal place.
1000 mL200 mL infused75 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: V = 210 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
35·62 = 2170 mL/day
Free water from the formula
45·24 = 1080 mL
1080·0.84 = 907.2 mL
Water still needed
2170 − 907.2 = 1263 mL/day
Volume per flush
24/4 = 6 flushes
V = 1263/6 = 210.5 ≈ 210 mL
Answer
V = 210 mL
2.Enteral & parenteral nutrition calculations
Answer: GIR = 2.7 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
17.5·1000/100 = 175 g = 175 000 mg
Minutes of infusion
24·60 = 1440 min
Glucose infusion rate
GIR = 175 000/(45·1440) = 2.701 ≈ 2.7 mg/kg/min
Answer
GIR = 2.7 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: 100 + 120 = 220 mL
ice chips: 120/2 = 60 mL
IV infusion: 75·12 = 900 mL
IV antibiotic: 2·100 = 200 mL
total intake = 1380 mL
Total output
400 + 400 + 450 + 100 + 200 = 1550 mL
Balance
B = 1380 − 1550 = −170 mL
Answer
B = −170 mL
Negative: the patient lost more fluid than went in.
4.IV fluids & fluid balance
Answer: t = 10.7 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.
Volume left
1000 − 200 = 800 mL
Time
t = 800/75 = 10.67 ≈ 10.7 h
Answer
t = 10.7 h
That is about 10 h 40 min, so the bag runs out at about 01:10.