Practice exercise (made-up values, not clinical guidance). Use the Devine formula to find the ideal body weight IBW of a woman who is 160 cm tall (1 in = 2.54 cm). Round to one decimal place.
160 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 2000 mL of parenteral nutrition with final concentrations of 25% 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.
2000 mLdextrose 25%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 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). Count ice chips as half their volume.
Practice exercise (made-up values, not clinical guidance). A 500 mL bag was started at 11:00 and runs by pump at 50 mL/h. How many mL V are left in the bag at 14:30?
500 mL50 mL/h11:00 → 14:30
V = mL
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: IBW = 52.4 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
160 cm/2.54 = 62.99 in
Ideal body weight (Devine)
IBW = 45.5 + 2.3·(62.99 − 60) = 52.38 ≈ 52.4 kg
Answer
IBW = 52.4 kg
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: 25·2000/100 = 500 g
amino acids: 6·2000/100 = 120 g
Kilocalories per component
dextrose: 500·3.4 = 1700 kcal
amino acids: 120·4 = 480 kcal
lipid: 500·2 = 1000 kcal
Non-protein kcal and nitrogen
NPC = 1700 + 1000 = 2700 kcal
N = 120/6.25 = 19.2 g
Ratio
NPC : N = 2700/19.2 = 140.6 ≈ 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: B = 1230 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 + 300 + 180 = 600 mL
ice chips: 120/2 = 60 mL
IV infusion: 100·12 = 1200 mL
IV antibiotic: 1·100 = 100 mL
total intake = 1960 mL
Total output
425 + 275 + 30 = 730 mL
Balance
B = 1960 − 730 = 1230 mL
Answer
B = 1230 mL
Positive: more fluid went in than came out.
4.IV fluids & fluid balance
Answer: V = 325 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.