Practice exercise (made-up values, not clinical guidance). A woman is 171 cm tall and weighs 88 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.
171 cm88 kgwoman
%IBW = %
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). A critically ill man is 182 cm tall and weighs 127 kg. The practice protocol gives 12 kcal/kg of actual body weight per day if the BMI is 30–50 kg/m², and 23 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 patient weighs 80 kg. Find the average urine output U in mL/kg/h. Round to two decimal places.
Practice exercise (made-up values, not clinical guidance). A 1000 mL infusion starts at 07:00 at 150 mL/h. After 2 hours the rate is changed to 50 mL/h and is not changed again. How many hours t after the start will the bag be empty? Round to one decimal place.
1000 mL150 mL/h · 2 h50 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: %IBW = 141 %
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)
171 cm/2.54 = 67.32 in
IBW = 45.5 + 2.3·(67.32 − 60) = 62.34 kg
Percentage of ideal body weight
%IBW = 88/62.34·100 = 141.2 ≈ 141%
Answer
%IBW = 141%
2.Enteral & parenteral nutrition calculations
Answer: E = 1524 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 = 127/1.82² = 38.34 kg/m²
Energy goal
BMI 30–50: kcal per kg of actual body weight.
E = 12·127 = 1524 kcal/day
Answer
E = 1524 kcal/day
3.IV fluids & fluid balance
Answer: U = 0.81 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
375 + 250 + 150 = 775 mL
Per kilogram per hour
U = 775/(80·12) = 0.8073 ≈ 0.81 mL/kg/h
Answer
U = 0.81 mL/kg/h
4.IV fluids & fluid balance
Answer: t = 16 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
150·2 = 300 mL
1000 − 300 = 700 mL left
Second part
700/50 = 14 h
Total time
t = 2 + 14 = 16 h
Answer
t = 16 h
That is about 16 h 00 min, so the bag runs out at about 23:00.