Practice exercise (made-up values, not clinical guidance). A 58 kg adult (BMI below 30) needs 35 kcal/kg/day. The tube feed provides 1 kcal/mL and runs by pump for 24 hours a day. At what rate R do you set the pump, in mL/h? Round to the nearest whole number.
58 kg35 kcal/kg/day1 kcal/mL24 h
R = mL/h
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 15% 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.
1200 mLdextrose 15%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 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 08:30 at 80 mL/h. After 3 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 mL80 mL/h · 3 h50 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: R = 85 mL/h
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.
Energy needed
E = 35·58 = 2030 kcal/day
Daily volume
V = 2030/1 = 2030 mL/day
Pump rate
R = 2030/24 = 84.58 ≈ 85 mL/h
Answer
R = 85 mL/h
2.Enteral & parenteral nutrition calculations
Answer: NPC : N = 121
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: 15·1200/100 = 180 g
amino acids: 5·1200/100 = 60 g
Kilocalories per component
dextrose: 180·3.4 = 612 kcal
amino acids: 60·4 = 240 kcal
lipid: 500·1.1 = 550 kcal
Non-protein kcal and nitrogen
NPC = 612 + 550 = 1162 kcal
N = 60/6.25 = 9.6 g
Ratio
NPC : N = 1162/9.6 = 121 : 1
Answer
NPC : N = 121
Ratios of about 150 : 1 are typical for stable patients; lower ratios give relatively more protein.
3.IV fluids & fluid balance
Answer: B = 595 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: 120 + 200 = 320 mL
IV infusion: 100·12 = 1200 mL
IV antibiotic: 1·50 = 50 mL
total intake = 1570 mL
Total output
450 + 350 + 175 = 975 mL
Balance
B = 1570 − 975 = 595 mL
Answer
B = 595 mL
Positive: more fluid went in than came out.
4.IV fluids & fluid balance
Answer: t = 18.2 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
80·3 = 240 mL
1000 − 240 = 760 mL left
Second part
760/50 = 15.2 h
Total time
t = 3 + 15.2 = 18.2 h
Answer
t = 18.2 h
That is about 18 h 12 min, so the bag runs out at about 02:42.