Practice exercise (made-up values, not clinical guidance). A 55 kg patient has a fluid goal of 35 mL/kg/day and receives all fluid through a feeding tube. The formula is 70% free water and runs at 55 mL/h for 18 hours a day. The rest of the fluid is given as water flushes every 4 hours. What volume V is each flush? Round to the nearest whole number.
55 kg35 mL/kg/day70%55 mL/h · 18 hevery 4 h
V = mL
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). A critically ill man is 188 cm tall and weighs 170 kg. The practice protocol gives 13 kcal/kg of actual body weight per day if the BMI is 30–50 kg/m², and 24 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 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 500 mL bag runs by pump at 60 mL/h. At 14:30, 250 mL have already been infused. How many hours t until the bag is empty? Round to one decimal place.
500 mL250 mL infused60 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: V = 205 mL
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.
Fluid goal
35·55 = 1925 mL/day
Free water from the formula
55·18 = 990 mL
990·0.7 = 693 mL
Water still needed
1925 − 693 = 1232 mL/day
Volume per flush
24/4 = 6 flushes
V = 1232/6 = 205.3 ≈ 205 mL
Answer
V = 205 mL
2.Enteral & parenteral nutrition calculations
Answer: E = 2210 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 = 170/1.88² = 48.1 kg/m²
Energy goal
BMI 30–50: kcal per kg of actual body weight.
E = 13·170 = 2210 kcal/day
Answer
E = 2210 kcal/day
3.IV fluids & fluid balance
Answer: B = −290 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: 150 + 120 + 150 = 420 mL
ice chips: 100/2 = 50 mL
IV infusion: 75·8 = 600 mL
IV antibiotic: 1·100 = 100 mL
total intake = 1170 mL
Total output
450 + 350 + 400 + 60 + 200 = 1460 mL
Balance
B = 1170 − 1460 = −290 mL
Answer
B = −290 mL
Negative: the patient lost more fluid than went in.
4.IV fluids & fluid balance
Answer: t = 4.2 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
500 − 250 = 250 mL
Time
t = 250/60 = 4.167 ≈ 4.2 h
Answer
t = 4.2 h
That is about 4 h 10 min, so the bag runs out at about 18:40.