Practice exercise (made-up values, not clinical guidance). A man is 175 cm tall and weighs 104 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.
175 cm104 kgman
%IBW = %
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). A critically ill man is 182 cm tall and weighs 183 kg. The practice protocol gives 2 g of protein per kg of ideal body weight (Devine) per day if the BMI is 30 to under 40 kg/m², and 2.5 g/kg of ideal body weight per day if the BMI is 40 kg/m² or more. Find the protein goal P in g/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 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 1000 mL bag runs by pump at 120 mL/h. At 11:30, 250 mL have already been infused. How many hours t until the bag is empty? Round to one decimal place.
1000 mL250 mL infused120 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: %IBW = 148 %
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)
175 cm/2.54 = 68.9 in
IBW = 50 + 2.3·(68.9 − 60) = 70.46 kg
Percentage of ideal body weight
%IBW = 104/70.46·100 = 147.6 ≈ 148%
Answer
%IBW = 148%
2.Enteral & parenteral nutrition calculations
Answer: P = 192 g/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). The protein goal is 2 g/kg of ideal body weight per day for BMI 30–40 and up to 2.5 g/kg of ideal body weight per day for BMI 40 and above. The numbers are for practice only; at the bedside always follow local protocols and have high-risk doses double-checked.
Body mass index
BMI = 183/1.82² = 55.25 kg/m²
Ideal body weight (Devine)
182 cm/2.54 = 71.65 in
IBW = 50 + 2.3·(71.65 − 60) = 76.8 kg
Protein goal
BMI 40 or more: 2.5 g per kg of ideal body weight.
P = 2.5·76.8 = 192 g/day
Answer
P = 192 g/day
3.IV fluids & fluid balance
Answer: I = 1450 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: 150 + 240 + 100 = 490 mL
ice chips: 120/2 = 60 mL
IV infusion: 100·8 = 800 mL
IV antibiotic: 1·100 = 100 mL
I = 1450 mL
Answer
I = 1450 mL
4.IV fluids & fluid balance
Answer: t = 6.3 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 − 250 = 750 mL
Time
t = 750/120 = 6.25 ≈ 6.3 h
Answer
t = 6.3 h
That is about 6 h 15 min, so the bag runs out at about 17:45.