Practice exercise (made-up values, not clinical guidance). An 83 kg patient needs 1.8 g of protein per kg a day. The tube feed contains 68 g of protein per litre and runs at 45 mL/h for 24 hours a day. How many grams of extra protein ΔP a day are still needed? Round to one decimal place.
83 kg1.8 g/kg/day68 g/L45 mL/h · 24 h
ΔP = g/day
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). An 80 kg adult receives 1000 mL of parenteral nutrition containing 20% dextrose, infused over 24 hours. Find the glucose infusion rate GIR in mg/kg/min. Round to two decimal places.
80 kg1000 mLdextrose 20%24 h
GIR = mg/kg/min
3.IV fluids & fluid balanceMedium
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 67 kg. Find the average urine output U in mL/kg/h. Round to two decimal places.
67 kg8 hurine: 325 mLurine: 175 mLwound drain: 80 mL
U = mL/kg/h
4.IV fluids & fluid balanceHard
Practice exercise (made-up values, not clinical guidance). A 1000 mL bag runs by pump at 125 mL/h. At 21:30, 750 mL have already been infused. How many hours t until the bag is empty? Round to one decimal place.
1000 mL750 mL infused125 mL/h
t = h
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: ΔP = 76 g/day
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.
Protein needed
1.8·83 = 149.4 g/day
Protein from the feed
45·24 = 1080 mL = 1.08 L
1.08·68 = 73.44 g/day
Shortfall
ΔP = 149.4 − 73.44 = 75.96 ≈ 76 g/day
Answer
ΔP = 76 g/day
2.Enteral & parenteral nutrition calculations
Answer: GIR = 1.74 mg/kg/min
Parenteral nutrition: dextrose provides 3.4 kcal/g, amino acids 4 kcal/g and lipid emulsion the kcal/mL stated (2 kcal/mL for 20%, 1.1 kcal/mL for 10%). Grams = % × mL/100. Non-protein kcal (NPC) = dextrose + lipid kcal; nitrogen = protein/6.25. The glucose infusion rate (GIR) in mg/kg/min = dextrose mg/(kg × minutes). The numbers are for practice only; at the bedside always follow local protocols and have high-risk doses double-checked.
Dextrose in the bag
20·1000/100 = 200 g = 200 000 mg
Minutes of infusion
24·60 = 1440 min
Glucose infusion rate
GIR = 200 000/(80·1440) = 1.736 ≈ 1.74 mg/kg/min
Answer
GIR = 1.74 mg/kg/min
3.IV fluids & fluid balance
Answer: U = 0.93 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
325 + 175 = 500 mL
Per kilogram per hour
U = 500/(67·8) = 0.9328 ≈ 0.93 mL/kg/h
Answer
U = 0.93 mL/kg/h
4.IV fluids & fluid balance
Answer: t = 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
1000 − 750 = 250 mL
Time
t = 250/125 = 2 h
Answer
t = 2 h
That is about 2 h 00 min, so the bag runs out at about 23:30.