Practice exercise (made-up values, not clinical guidance). A woman is 178 cm tall and weighs 91 kg. Find the actual weight as a percentage of the ideal body weight, %IBW, using the Devine formula (1 in = 2.54 cm). Round to the nearest whole number.
178 cm91 kgwoman
%IBW = %
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). A 105 kg adult receives 1800 mL of parenteral nutrition containing 25% dextrose, infused over 24 hours. Find the glucose infusion rate GIR in mg/kg/min. Round to two decimal places.
105 kg1800 mLdextrose 25%24 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 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 100 mL/h. At 12:30, 100 mL have already been infused. How many hours t until the bag is empty? Round to one decimal place.
500 mL100 mL infused100 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: %IBW = 132 %
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.
Ideal body weight (Devine)
178 cm/2.54 = 70.08 in
IBW = 45.5 + 2.3·(70.08 − 60) = 68.68 kg
Percentage of ideal body weight
%IBW = 91/68.68·100 = 132.5 ≈ 132%
Answer
%IBW = 132%
2.Enteral & parenteral nutrition calculations
Answer: GIR = 2.98 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
25·1800/100 = 450 g = 450 000 mg
Minutes of infusion
24·60 = 1440 min
Glucose infusion rate
GIR = 450 000/(105·1440) = 2.976 ≈ 2.98 mg/kg/min
Answer
GIR = 2.98 mg/kg/min
3.IV fluids & fluid balance
Answer: B = 430 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: 200 + 150 + 120 = 470 mL
IV infusion: 125·8 = 1000 mL
IV antibiotic: 1·100 = 100 mL
total intake = 1570 mL
Total output
475 + 450 + 175 + 40 = 1140 mL
Balance
B = 1570 − 1140 = 430 mL
Answer
B = 430 mL
Positive: more fluid went in than came out.
4.IV fluids & fluid balance
Answer: t = 4 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 − 100 = 400 mL
Time
t = 400/100 = 4 h
Answer
t = 4 h
That is about 4 h 00 min, so the bag runs out at about 16:30.