Practice exercise (made-up values, not clinical guidance). Use the Devine formula to find the ideal body weight IBW of a man who is 164 cm tall (1 in = 2.54 cm). Round to one decimal place.
164 cmman1 in = 2.54 cm
IBW = kg
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). Over 24 hours a patient receives 1500 mL of parenteral nutrition with final concentrations of 15% dextrose and 5% amino acids, plus 500 mL of 20% lipid emulsion (2 kcal/mL). Find the non-protein kilocalorie to nitrogen ratio NPC : N (the number x in x : 1). Round to the nearest whole number.
1500 mLdextrose 15%amino acids 5%lipid 500 mL · 2 kcal/mL
NPC : N =
3.IV fluids & fluid balanceMedium
Practice exercise (made-up values, not clinical guidance). The record shows a patient's intake and output for one 12-hour shift. The IV infusion ran at the rate shown for the whole shift. Find the total intake I in mL. Count ice chips as half their volume.
juice: 120 mLsoup: 180 mLice chips: 240 mLIV infusion: 125 mL/h × 12 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 14:00 and runs by pump at 50 mL/h. How many mL V are left in the bag at 17:30?
500 mL50 mL/h14:00 → 17:30
V = mL
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: IBW = 60.5 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
164 cm/2.54 = 64.57 in
Ideal body weight (Devine)
IBW = 50 + 2.3·(64.57 − 60) = 60.5 kg
Answer
IBW = 60.5 kg
2.Enteral & parenteral nutrition calculations
Answer: NPC : N = 147
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.
Grams of dextrose and amino acids
dextrose: 15·1500/100 = 225 g
amino acids: 5·1500/100 = 75 g
Kilocalories per component
dextrose: 225·3.4 = 765 kcal
amino acids: 75·4 = 300 kcal
lipid: 500·2 = 1000 kcal
Non-protein kcal and nitrogen
NPC = 765 + 1000 = 1765 kcal
N = 75/6.25 = 12 g
Ratio
NPC : N = 1765/12 = 147.1 ≈ 147 : 1
Answer
NPC : N = 147
Ratios of about 150 : 1 are typical for stable patients; lower ratios give relatively more protein.
3.IV fluids & fluid balance
Answer: I = 2020 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: 120 + 180 = 300 mL
ice chips: 240/2 = 120 mL
IV infusion: 125·12 = 1500 mL
IV antibiotic: 2·50 = 100 mL
I = 2020 mL
Answer
I = 2020 mL
4.IV fluids & fluid balance
Answer: V = 325 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.