Practice exercise (made-up values, not clinical guidance). A 78 kg patient has a fluid goal of 30 mL/kg/day and receives all fluid through a feeding tube. The formula is 84% free water and runs at 90 mL/h for 24 hours a day. The rest of the fluid is given as water flushes every 8 hours. What volume V is each flush? Round to the nearest whole number.
78 kg30 mL/kg/day84%90 mL/h · 24 hevery 8 h
V = mL
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). Over 24 hours a patient receives 1500 mL of parenteral nutrition with final concentrations of 12.5% dextrose and 5% amino acids, plus 500 mL of 10% lipid emulsion (1.1 kcal/mL). Find the non-protein kilocalorie to nitrogen ratio NPC : N (the number x in x : 1). Round to the nearest whole number.
1500 mLdextrose 12.5%amino acids 5%lipid 500 mL · 1.1 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 8-hour shift. The patient weighs 87 kg. Find the average urine output U in mL/kg/h. Round to two decimal places.
87 kg8 hurine: 400 mLurine: 400 mLurine: 300 mL
U = mL/kg/h
4.IV fluids & fluid balanceHard
Practice exercise (made-up values, not clinical guidance). A 1000 mL infusion starts at 09:00 at 75 mL/h. After 3 hours the rate is changed to 80 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 · 3 h80 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: V = 175 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
30·78 = 2340 mL/day
Free water from the formula
90·24 = 2160 mL
2160·0.84 = 1814 mL
Water still needed
2340 − 1814 = 525.6 mL/day
Volume per flush
24/8 = 3 flushes
V = 525.6/3 = 175.2 ≈ 175 mL
Answer
V = 175 mL
2.Enteral & parenteral nutrition calculations
Answer: NPC : N = 99
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: 12.5·1500/100 = 187.5 g
amino acids: 5·1500/100 = 75 g
Kilocalories per component
dextrose: 187.5·3.4 = 637.5 kcal
amino acids: 75·4 = 300 kcal
lipid: 500·1.1 = 550 kcal
Non-protein kcal and nitrogen
NPC = 637.5 + 550 = 1188 kcal
N = 75/6.25 = 12 g
Ratio
NPC : N = 1188/12 = 98.96 ≈ 99 : 1
Answer
NPC : N = 99
Ratios of about 150 : 1 are typical for stable patients; lower ratios give relatively more protein.
3.IV fluids & fluid balance
Answer: U = 1.58 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
400 + 400 + 300 = 1100 mL
Per kilogram per hour
U = 1100/(87·8) = 1.58 mL/kg/h
Answer
U = 1.58 mL/kg/h
4.IV fluids & fluid balance
Answer: t = 12.7 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
75·3 = 225 mL
1000 − 225 = 775 mL left
Second part
775/80 = 9.688 h
Total time
t = 3 + 9.688 = 12.69 ≈ 12.7 h
Answer
t = 12.7 h
That is about 12 h 41 min, so the bag runs out at about 21:41.