Practice exercise (made-up values, not clinical guidance). A woman is 169 cm tall and weighs 93 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.
169 cm93 kgwoman
%IBW = %
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). A critically ill woman is 177 cm tall and weighs 121 kg. The practice protocol gives 13 kcal/kg of actual body weight per day if the BMI is 30–50 kg/m², and 24 kcal/kg of ideal body weight (Devine) per day if the BMI is above 50 kg/m². Find the energy goal E in kcal/day. Round to the nearest whole number.
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 total intake I in mL. Count ice chips as half their volume.
Practice exercise (made-up values, not clinical guidance). A 1000 mL bag runs by pump at 75 mL/h. At 10:00, 750 mL have already been infused. How many hours t until the bag is empty? Round to one decimal place.
1000 mL750 mL infused75 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: %IBW = 154 %
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)
169 cm/2.54 = 66.54 in
IBW = 45.5 + 2.3·(66.54 − 60) = 60.53 kg
Percentage of ideal body weight
%IBW = 93/60.53·100 = 153.6 ≈ 154%
Answer
%IBW = 154%
2.Enteral & parenteral nutrition calculations
Answer: E = 1573 kcal/day
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. Obesity in critical illness (ASPEN/SCCM 2016): BMI = weight/height² (kg/m²). For BMI 30–50 the energy goal is 11–14 kcal/kg of actual body weight per day; above 50 it is 22–25 kcal/kg of ideal body weight per day. The numbers are for practice only; at the bedside always follow local protocols and have high-risk doses double-checked.
Body mass index
BMI = 121/1.77² = 38.62 kg/m²
Energy goal
BMI 30–50: kcal per kg of actual body weight.
E = 13·121 = 1573 kcal/day
Answer
E = 1573 kcal/day
3.IV fluids & fluid balance
Answer: I = 1670 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 + 250 + 100 = 550 mL
ice chips: 240/2 = 120 mL
IV infusion: 75·12 = 900 mL
IV antibiotic: 2·50 = 100 mL
I = 1670 mL
Answer
I = 1670 mL
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
1000 − 750 = 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 13:20.