Practice exercise (made-up values, not clinical guidance). Use the Devine formula to find the ideal body weight IBW of a woman who is 165 cm tall (1 in = 2.54 cm). Round to one decimal place.
165 cmwoman1 in = 2.54 cm
IBW = kg
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). Over 24 hours a patient receives 2400 mL of parenteral nutrition with final concentrations of 10% dextrose and 6% 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.
2400 mLdextrose 10%amino acids 6%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 IV infusion ran at the rate shown for the whole shift. Find the total intake I in mL.
juice: 120 mLsoup: 250 mLtea: 150 mLIV infusion: 100 mL/h × 8 hIV antibiotic: 1 × 100 mL
I = mL
4.IV fluids & fluid balanceHard
Practice exercise (made-up values, not clinical guidance). A 1000 mL bag runs by pump at 100 mL/h. At 15:30, 50 mL have already been infused. How many hours t until the bag is empty? Round to one decimal place.
1000 mL50 mL infused100 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: IBW = 56.9 kg
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.
Height in inches
165 cm/2.54 = 64.96 in
Ideal body weight (Devine)
IBW = 45.5 + 2.3·(64.96 − 60) = 56.91 ≈ 56.9 kg
Answer
IBW = 56.9 kg
2.Enteral & parenteral nutrition calculations
Answer: NPC : N = 59
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: 10·2400/100 = 240 g
amino acids: 6·2400/100 = 144 g
Kilocalories per component
dextrose: 240·3.4 = 816 kcal
amino acids: 144·4 = 576 kcal
lipid: 500·1.1 = 550 kcal
Non-protein kcal and nitrogen
NPC = 816 + 550 = 1366 kcal
N = 144/6.25 = 23.04 g
Ratio
NPC : N = 1366/23.04 = 59.29 ≈ 59 : 1
Answer
NPC : N = 59
Ratios of about 150 : 1 are typical for stable patients; lower ratios give relatively more protein.
3.IV fluids & fluid balance
Answer: I = 1420 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.
Add the intake
oral: 120 + 250 + 150 = 520 mL
IV infusion: 100·8 = 800 mL
IV antibiotic: 1·100 = 100 mL
I = 1420 mL
Answer
I = 1420 mL
4.IV fluids & fluid balance
Answer: t = 9.5 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
1000 − 50 = 950 mL
Time
t = 950/100 = 9.5 h
Answer
t = 9.5 h
That is about 9 h 30 min, so the bag runs out at about 01:00.