Practice exercise (made-up values, not clinical guidance). Use the Devine formula to find the ideal body weight IBW of a man who is 184 cm tall (1 in = 2.54 cm). Round to one decimal place.
184 cmman1 in = 2.54 cm
IBW = kg
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). A critically ill woman is 172 cm tall and weighs 137 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.
tea: 240 mLsoup: 250 mLmilk: 240 mLIV infusion: 100 mL/h × 8 hIV antibiotic: 2 × 50 mL
I = mL
4.IV fluids & fluid balanceHard
Practice exercise (made-up values, not clinical guidance). A 500 mL bag was started at 13:45 and runs by pump at 120 mL/h. How many mL V are left in the bag at 15:15?
500 mL120 mL/h13:45 → 15:15
V = mL
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: IBW = 78.6 kg
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.
Height in inches
184 cm/2.54 = 72.44 in
Ideal body weight (Devine)
IBW = 50 + 2.3·(72.44 − 60) = 78.61 ≈ 78.6 kg
Answer
IBW = 78.6 kg
2.Enteral & parenteral nutrition calculations
Answer: P = 158 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 = 137/1.72² = 46.31 kg/m²
Ideal body weight (Devine)
172 cm/2.54 = 67.72 in
IBW = 45.5 + 2.3·(67.72 − 60) = 63.25 kg
Protein goal
BMI 40 or more: 2.5 g per kg of ideal body weight.
P = 2.5·63.25 = 158.1 ≈ 158 g/day
Answer
P = 158 g/day
3.IV fluids & fluid balance
Answer: I = 1630 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 + 250 + 240 = 730 mL
IV infusion: 100·8 = 800 mL
IV antibiotic: 2·50 = 100 mL
I = 1630 mL
Answer
I = 1630 mL
4.IV fluids & fluid balance
Answer: V = 320 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.