Practice exercise (made-up values, not clinical guidance). Use the Devine formula to find the ideal body weight IBW of a woman who is 158 cm tall (1 in = 2.54 cm). Round to one decimal place.
158 cmwoman1 in = 2.54 cm
IBW = kg
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). A child who weighs 7.5 kg receives 10% dextrose at 19 mL/h. Find the glucose infusion rate GIR in mg/kg/min. Round to two decimal places.
7.5 kg10%19 mL/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 12-hour shift. The patient weighs 110 kg. Find the average urine output U in mL/kg/h. Round to two decimal places.
110 kg12 hurine: 225 mLurine: 350 mL
U = mL/kg/h
4.IV fluids & fluid balanceHard
Practice exercise (made-up values, not clinical guidance). A 500 mL bag runs by pump at 75 mL/h. At 10:30, 250 mL have already been infused. How many hours t until the bag is empty? Round to one decimal place.
500 mL250 mL infused75 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: IBW = 50.6 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
158 cm/2.54 = 62.2 in
Ideal body weight (Devine)
IBW = 45.5 + 2.3·(62.2 − 60) = 50.57 ≈ 50.6 kg
Answer
IBW = 50.6 kg
2.Enteral & parenteral nutrition calculations
Answer: GIR = 4.22 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 concentration
10% = 100 mg/mL
Dextrose per minute
100·19/60 = 31.67 mg/min
Per kilogram
GIR = 31.67/7.5 = 4.222 ≈ 4.22 mg/kg/min
Answer
GIR = 4.22 mg/kg/min
Shortcut: GIR = % dextrose × mL/h/(6 × kg).
3.IV fluids & fluid balance
Answer: U = 0.44 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
225 + 350 = 575 mL
Per kilogram per hour
U = 575/(110·12) = 0.4356 ≈ 0.44 mL/kg/h
Answer
U = 0.44 mL/kg/h
4.IV fluids & fluid balance
Answer: t = 3.3 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 − 250 = 250 mL
Time
t = 250/75 = 3.333 ≈ 3.3 h
Answer
t = 3.3 h
That is about 3 h 20 min, so the bag runs out at about 13:50.