Practice exercise (made-up values, not clinical guidance). An 83 kg adult (BMI below 30) needs 25 kcal/kg/day. The tube feed provides 2 kcal/mL and runs by pump for 20 hours a day. At what rate R do you set the pump, in mL/h? Round to the nearest whole number.
83 kg25 kcal/kg/day2 kcal/mL20 h
R = mL/h
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). Over 24 hours a patient receives 2000 mL of parenteral nutrition with final concentrations of 10% dextrose and 6% amino acids, plus 250 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.
2000 mLdextrose 10%amino acids 6%lipid 250 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 8-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 bag runs by pump at 50 mL/h. At 16:30, 450 mL have already been infused. How many hours t until the bag is empty? Round to one decimal place.
1000 mL450 mL infused50 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: R = 52 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 = 25·83 = 2075 kcal/day
Daily volume
V = 2075/2 = 1038 mL/day
Pump rate
R = 1038/20 = 51.88 ≈ 52 mL/h
Answer
R = 52 mL/h
2.Enteral & parenteral nutrition calculations
Answer: NPC : N = 61
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: 10·2000/100 = 200 g
amino acids: 6·2000/100 = 120 g
Kilocalories per component
dextrose: 200·3.4 = 680 kcal
amino acids: 120·4 = 480 kcal
lipid: 250·2 = 500 kcal
Non-protein kcal and nitrogen
NPC = 680 + 500 = 1180 kcal
N = 120/6.25 = 19.2 g
Ratio
NPC : N = 1180/19.2 = 61.46 ≈ 61 : 1
Answer
NPC : N = 61
Ratios of about 150 : 1 are typical for stable patients; lower ratios give relatively more protein.
3.IV fluids & fluid balance
Answer: B = −260 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: 200 + 300 + 100 = 600 mL
IV infusion: 75·8 = 600 mL
IV antibiotic: 2·50 = 100 mL
total intake = 1300 mL
Total output
400 + 500 + 250 + 150 + 110 + 150 = 1560 mL
Balance
B = 1300 − 1560 = −260 mL
Answer
B = −260 mL
Negative: the patient lost more fluid than went in.
4.IV fluids & fluid balance
Answer: t = 11 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 − 450 = 550 mL
Time
t = 550/50 = 11 h
Answer
t = 11 h
That is about 11 h 00 min, so the bag runs out at about 03:30.