Practice exercise (made-up values, not clinical guidance). A 55 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 75 mL/h for 20 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.
55 kg35 mL/kg/day84%75 mL/h · 20 hevery 8 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 12.5% dextrose and 6% amino acids, plus 500 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 12.5%amino acids 6%lipid 500 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 52 kg. Find the average urine output U in mL/kg/h. Round to two decimal places.
Practice exercise (made-up values, not clinical guidance). A 500 mL bag was started at 13:45 and runs by pump at 60 mL/h. How many mL V are left in the bag at 18:15?
500 mL60 mL/h13:45 → 18:15
V = mL
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: V = 222 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
35·55 = 1925 mL/day
Free water from the formula
75·20 = 1500 mL
1500·0.84 = 1260 mL
Water still needed
1925 − 1260 = 665 mL/day
Volume per flush
24/8 = 3 flushes
V = 665/3 = 221.7 ≈ 222 mL
Answer
V = 222 mL
2.Enteral & parenteral nutrition calculations
Answer: NPC : N = 131
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: 12.5·1200/100 = 150 g
amino acids: 6·1200/100 = 72 g
Kilocalories per component
dextrose: 150·3.4 = 510 kcal
amino acids: 72·4 = 288 kcal
lipid: 500·2 = 1000 kcal
Non-protein kcal and nitrogen
NPC = 510 + 1000 = 1510 kcal
N = 72/6.25 = 11.52 g
Ratio
NPC : N = 1510/11.52 = 131.1 ≈ 131 : 1
Answer
NPC : N = 131
Ratios of about 150 : 1 are typical for stable patients; lower ratios give relatively more protein.
3.IV fluids & fluid balance
Answer: U = 2 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
350 + 250 + 150 + 500 = 1250 mL
Per kilogram per hour
U = 1250/(52·12) = 2.003 ≈ 2 mL/kg/h
Answer
U = 2 mL/kg/h
4.IV fluids & fluid balance
Answer: V = 230 mL
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.