Practice exercise (made-up values, not clinical guidance). A woman is 164 cm tall and weighs 42 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.
164 cm42 kgwoman
%IBW = %
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). A critically ill man is 168 cm tall and weighs 115 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.
milk: 240 mLsoup: 200 mLIV infusion: 75 mL/h × 8 hIV antibiotic: 1 × 100 mL
I = mL
4.IV fluids & fluid balanceHard
Practice exercise (made-up values, not clinical guidance). A 1000 mL bag was started at 12:00 and runs by pump at 125 mL/h. How many mL V are left in the bag at 13:00?
1000 mL125 mL/h12:00 → 13:00
V = mL
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: %IBW = 75 %
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)
164 cm/2.54 = 64.57 in
IBW = 45.5 + 2.3·(64.57 − 60) = 56 kg
Percentage of ideal body weight
%IBW = 42/56·100 = 74.99 ≈ 75%
Answer
%IBW = 75%
2.Enteral & parenteral nutrition calculations
Answer: P = 160 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 = 115/1.68² = 40.75 kg/m²
Ideal body weight (Devine)
168 cm/2.54 = 66.14 in
IBW = 50 + 2.3·(66.14 − 60) = 64.13 kg
Protein goal
BMI 40 or more: 2.5 g per kg of ideal body weight.
P = 2.5·64.13 = 160.3 ≈ 160 g/day
Answer
P = 160 g/day
3.IV fluids & fluid balance
Answer: I = 1140 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: 240 + 200 = 440 mL
IV infusion: 75·8 = 600 mL
IV antibiotic: 1·100 = 100 mL
I = 1140 mL
Answer
I = 1140 mL
4.IV fluids & fluid balance
Answer: V = 875 mL
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.