Practice exercise (made-up values, not clinical guidance). Use the Devine formula to find the ideal body weight IBW of a man who is 177 cm tall (1 in = 2.54 cm). Round to one decimal place.
177 cmman1 in = 2.54 cm
IBW = kg
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). A 79 kg adult receives 1800 mL of parenteral nutrition containing 12.5% dextrose, infused over 16 hours. Find the glucose infusion rate GIR in mg/kg/min. Round to two decimal places.
79 kg1800 mLdextrose 12.5%16 h
GIR = mg/kg/min
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. Count ice chips as half their volume.
Practice exercise (made-up values, not clinical guidance). A 500 mL infusion starts at 11:00 at 100 mL/h. After 4 hours the rate is changed to 200 mL/h and is not changed again. How many hours t after the start will the bag be empty? Round to one decimal place.
500 mL100 mL/h · 4 h200 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: IBW = 72.3 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
177 cm/2.54 = 69.69 in
Ideal body weight (Devine)
IBW = 50 + 2.3·(69.69 − 60) = 72.28 ≈ 72.3 kg
Answer
IBW = 72.3 kg
2.Enteral & parenteral nutrition calculations
Answer: GIR = 2.97 mg/kg/min
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.
Dextrose in the bag
12.5·1800/100 = 225 g = 225 000 mg
Minutes of infusion
16·60 = 960 min
Glucose infusion rate
GIR = 225 000/(79·960) = 2.967 ≈ 2.97 mg/kg/min
Answer
GIR = 2.97 mg/kg/min
3.IV fluids & fluid balance
Answer: I = 1400 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: 200 + 200 + 200 = 600 mL
ice chips: 200/2 = 100 mL
IV infusion: 75·8 = 600 mL
IV antibiotic: 2·50 = 100 mL
I = 1400 mL
Answer
I = 1400 mL
4.IV fluids & fluid balance
Answer: t = 4.5 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.
First part
100·4 = 400 mL
500 − 400 = 100 mL left
Second part
100/200 = 0.5 h
Total time
t = 4 + 0.5 = 4.5 h
Answer
t = 4.5 h
That is about 4 h 30 min, so the bag runs out at about 15:30.