Practice exercise (made-up values, not clinical guidance). A 59 kg adult (BMI below 30) needs 25 kcal/kg/day. The tube feed provides 1 kcal/mL and runs by pump for 24 hours a day. At what rate R do you set the pump, in mL/h? Round to the nearest whole number.
59 kg25 kcal/kg/day1 kcal/mL24 h
R = mL/h
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). A critically ill man is 176 cm tall and weighs 178 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 fluid balance B = intake − output in mL (a negative answer means a net loss). Count ice chips as half their volume.
Practice exercise (made-up values, not clinical guidance). A 1000 mL infusion starts at 11:00 at 125 mL/h. After 4 hours the rate is changed to 75 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 mL125 mL/h · 4 h75 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: R = 61 mL/h
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.
Energy needed
E = 25·59 = 1475 kcal/day
Daily volume
V = 1475/1 = 1475 mL/day
Pump rate
R = 1475/24 = 61.46 ≈ 61 mL/h
Answer
R = 61 mL/h
2.Enteral & parenteral nutrition calculations
Answer: P = 178 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 = 178/1.76² = 57.46 kg/m²
Ideal body weight (Devine)
176 cm/2.54 = 69.29 in
IBW = 50 + 2.3·(69.29 − 60) = 71.37 kg
Protein goal
BMI 40 or more: 2.5 g per kg of ideal body weight.
P = 2.5·71.37 = 178.4 ≈ 178 g/day
Answer
P = 178 g/day
3.IV fluids & fluid balance
Answer: B = −105 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.
Total intake
oral: 240 + 150 = 390 mL
ice chips: 240/2 = 120 mL
IV infusion: 75·8 = 600 mL
IV antibiotic: 1·100 = 100 mL
total intake = 1210 mL
Total output
325 + 400 + 150 + 400 + 40 = 1315 mL
Balance
B = 1210 − 1315 = −105 mL
Answer
B = −105 mL
Negative: the patient lost more fluid than went in.
4.IV fluids & fluid balance
Answer: t = 10.7 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
125·4 = 500 mL
1000 − 500 = 500 mL left
Second part
500/75 = 6.667 h
Total time
t = 4 + 6.667 = 10.67 ≈ 10.7 h
Answer
t = 10.7 h
That is about 10 h 40 min, so the bag runs out at about 21:40.