Practice exercise (made-up values, not clinical guidance). A 71 kg adult (BMI below 30) needs 25 kcal/kg/day. The tube feed provides 1.5 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.
71 kg25 kcal/kg/day1.5 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 1500 mL of parenteral nutrition with final concentrations of 17.5% dextrose and 4.25% 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 17.5%amino acids 4.25%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 103 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 runs by pump at 100 mL/h. At 21:00, 150 mL have already been infused. How many hours t until the bag is empty? Round to one decimal place.
500 mL150 mL infused100 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: R = 49 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 = 25·71 = 1775 kcal/day
Daily volume
V = 1775/1.5 = 1183 mL/day
Pump rate
R = 1183/24 = 49.31 ≈ 49 mL/h
Answer
R = 49 mL/h
2.Enteral & parenteral nutrition calculations
Answer: NPC : N = 141
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: 17.5·1500/100 = 262.5 g
amino acids: 4.25·1500/100 = 63.75 g
Kilocalories per component
dextrose: 262.5·3.4 = 892.5 kcal
amino acids: 63.75·4 = 255 kcal
lipid: 500·1.1 = 550 kcal
Non-protein kcal and nitrogen
NPC = 892.5 + 550 = 1443 kcal
N = 63.75/6.25 = 10.2 g
Ratio
NPC : N = 1443/10.2 = 141.4 ≈ 141 : 1
Answer
NPC : N = 141
Ratios of about 150 : 1 are typical for stable patients; lower ratios give relatively more protein.
3.IV fluids & fluid balance
Answer: U = 1 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 + 475 = 825 mL
Per kilogram per hour
U = 825/(103·8) = 1.001 ≈ 1 mL/kg/h
Answer
U = 1 mL/kg/h
4.IV fluids & fluid balance
Answer: t = 3.5 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.
Volume left
500 − 150 = 350 mL
Time
t = 350/100 = 3.5 h
Answer
t = 3.5 h
That is about 3 h 30 min, so the bag runs out at about 00:30.