Practice exercise (made-up values, not clinical guidance). A 61 kg patient has a fluid goal of 30 mL/kg/day and receives all fluid through a feeding tube. The formula is 81% free water and runs at 75 mL/h for 18 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.
61 kg30 mL/kg/day81%75 mL/h · 18 hevery 6 h
V = mL
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). Over 24 hours a patient receives 1200 mL of parenteral nutrition with final concentrations of 10% dextrose and 3.5% amino acids, plus 100 mL of 20% lipid emulsion (2 kcal/mL). Find the non-protein kilocalorie to nitrogen ratio NPC : N (the number x in x : 1). Round to the nearest whole number.
1200 mLdextrose 10%amino acids 3.5%lipid 100 mL · 2 kcal/mL
NPC : N =
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 88 kg. Find the average urine output U in mL/kg/h. Round to two decimal places.
88 kg12 hurine: 425 mLurine: 225 mLvomit: 200 mL
U = mL/kg/h
4.IV fluids & fluid balanceHard
Practice exercise (made-up values, not clinical guidance). A 1000 mL infusion starts at 08:00 at 75 mL/h. After 4 hours the rate is changed to 200 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 h200 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: V = 184 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
30·61 = 1830 mL/day
Free water from the formula
75·18 = 1350 mL
1350·0.81 = 1094 mL
Water still needed
1830 − 1094 = 736.5 mL/day
Volume per flush
24/6 = 4 flushes
V = 736.5/4 = 184.1 ≈ 184 mL
Answer
V = 184 mL
2.Enteral & parenteral nutrition calculations
Answer: NPC : N = 90
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.
Grams of dextrose and amino acids
dextrose: 10·1200/100 = 120 g
amino acids: 3.5·1200/100 = 42 g
Kilocalories per component
dextrose: 120·3.4 = 408 kcal
amino acids: 42·4 = 168 kcal
lipid: 100·2 = 200 kcal
Non-protein kcal and nitrogen
NPC = 408 + 200 = 608 kcal
N = 42/6.25 = 6.72 g
Ratio
NPC : N = 608/6.72 = 90.48 ≈ 90 : 1
Answer
NPC : N = 90
Ratios of about 150 : 1 are typical for stable patients; lower ratios give relatively more protein.
3.IV fluids & fluid balance
Answer: U = 0.62 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
425 + 225 = 650 mL
Per kilogram per hour
U = 650/(88·12) = 0.6155 ≈ 0.62 mL/kg/h
Answer
U = 0.62 mL/kg/h
4.IV fluids & fluid balance
Answer: t = 7.5 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
75·4 = 300 mL
1000 − 300 = 700 mL left
Second part
700/200 = 3.5 h
Total time
t = 4 + 3.5 = 7.5 h
Answer
t = 7.5 h
That is about 7 h 30 min, so the bag runs out at about 15:30.