Practice exercise (made-up values, not clinical guidance). Use the Devine formula to find the ideal body weight IBW of a woman who is 161 cm tall (1 in = 2.54 cm). Round to one decimal place.
161 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 1200 mL of parenteral nutrition with final concentrations of 15% dextrose and 3.5% amino acids, plus 250 mL of 10% lipid emulsion (1.1 kcal/mL). Find the total energy E the patient receives in kcal per day. Round to the nearest whole number.
1200 mLdextrose 15%amino acids 3.5%lipid 250 mL · 1.1 kcal/mL
E = kcal/day
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 500 mL bag runs by pump at 75 mL/h. At 07:30, 300 mL have already been infused. How many hours t until the bag is empty? Round to one decimal place.
500 mL300 mL infused75 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: IBW = 53.3 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
161 cm/2.54 = 63.39 in
Ideal body weight (Devine)
IBW = 45.5 + 2.3·(63.39 − 60) = 53.29 ≈ 53.3 kg
Answer
IBW = 53.3 kg
2.Enteral & parenteral nutrition calculations
Answer: E = 1055 kcal/day
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: 3.5·1200/100 = 42 g
Kilocalories per component
dextrose: 180·3.4 = 612 kcal
amino acids: 42·4 = 168 kcal
lipid: 250·1.1 = 275 kcal
Total energy
E = 612 + 168 + 275 = 1055 kcal/day
Answer
E = 1055 kcal/day
3.IV fluids & fluid balance
Answer: B = −35 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 + 250 = 370 mL
IV infusion: 80·12 = 960 mL
IV antibiotic: 1·50 = 50 mL
total intake = 1380 mL
Total output
375 + 350 + 400 + 90 + 200 = 1415 mL
Balance
B = 1380 − 1415 = −35 mL
Answer
B = −35 mL
Negative: the patient lost more fluid than went in.
4.IV fluids & fluid balance
Answer: t = 2.7 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 − 300 = 200 mL
Time
t = 200/75 = 2.667 ≈ 2.7 h
Answer
t = 2.7 h
That is about 2 h 40 min, so the bag runs out at about 10:10.