Practice exercise (made-up values, not clinical guidance). An 87 kg patient has a fluid goal of 35 mL/kg/day and receives all fluid through a feeding tube. The formula is 81% free water and runs at 85 mL/h for 24 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.
87 kg35 mL/kg/day81%85 mL/h · 24 hevery 4 h
V = mL
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). A critically ill woman is 160 cm tall and weighs 84 kg. The practice protocol gives 12 kcal/kg of actual body weight per day if the BMI is 30–50 kg/m², and 22 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 patient weighs 107 kg. Find the average urine output U in mL/kg/h. Round to two decimal places.
107 kg8 hurine: 400 mLurine: 150 mLurine: 225 mL
U = mL/kg/h
4.IV fluids & fluid balanceHard
Practice exercise (made-up values, not clinical guidance). A 500 mL bag runs by pump at 100 mL/h. At 15:00, 100 mL have already been infused. How many hours t until the bag is empty? Round to one decimal place.
500 mL100 mL infused100 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: V = 232 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
35·87 = 3045 mL/day
Free water from the formula
85·24 = 2040 mL
2040·0.81 = 1652 mL
Water still needed
3045 − 1652 = 1393 mL/day
Volume per flush
24/4 = 6 flushes
V = 1393/6 = 232.1 ≈ 232 mL
Answer
V = 232 mL
2.Enteral & parenteral nutrition calculations
Answer: E = 1008 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 = 84/1.6² = 32.81 kg/m²
Energy goal
BMI 30–50: kcal per kg of actual body weight.
E = 12·84 = 1008 kcal/day
Answer
E = 1008 kcal/day
3.IV fluids & fluid balance
Answer: U = 0.91 mL/kg/h
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 urine
400 + 150 + 225 = 775 mL
Per kilogram per hour
U = 775/(107·8) = 0.9054 ≈ 0.91 mL/kg/h
Answer
U = 0.91 mL/kg/h
4.IV fluids & fluid balance
Answer: t = 4 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 − 100 = 400 mL
Time
t = 400/100 = 4 h
Answer
t = 4 h
That is about 4 h 00 min, so the bag runs out at about 19:00.