Practice exercise (made-up values, not clinical guidance). Use the Devine formula to find the ideal body weight IBW of a woman who is 154 cm tall (1 in = 2.54 cm). Round to one decimal place.
154 cmwoman1 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 1000 mL of parenteral nutrition with final concentrations of 25% dextrose and 6% amino acids, plus 500 mL of 10% lipid emulsion (1.1 kcal/mL). Find the non-protein kilocalorie to nitrogen ratio NPC : N (the number x in x : 1). Round to the nearest whole number.
1000 mLdextrose 25%amino acids 6%lipid 500 mL · 1.1 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 fluid balance B = intake − output in mL (a negative answer means a net loss).
Practice exercise (made-up values, not clinical guidance). A 500 mL bag was started at 10:45 and runs by pump at 75 mL/h. How many mL V are left in the bag at 14:45?
500 mL75 mL/h10:45 → 14:45
V = mL
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: IBW = 46.9 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
154 cm/2.54 = 60.63 in
Ideal body weight (Devine)
IBW = 45.5 + 2.3·(60.63 − 60) = 46.95 ≈ 46.9 kg
Answer
IBW = 46.9 kg
2.Enteral & parenteral nutrition calculations
Answer: NPC : N = 146
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: 25·1000/100 = 250 g
amino acids: 6·1000/100 = 60 g
Kilocalories per component
dextrose: 250·3.4 = 850 kcal
amino acids: 60·4 = 240 kcal
lipid: 500·1.1 = 550 kcal
Non-protein kcal and nitrogen
NPC = 850 + 550 = 1400 kcal
N = 60/6.25 = 9.6 g
Ratio
NPC : N = 1400/9.6 = 145.8 ≈ 146 : 1
Answer
NPC : N = 146
Ratios of about 150 : 1 are typical for stable patients; lower ratios give relatively more protein.
3.IV fluids & fluid balance
Answer: B = 755 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 + 150 + 200 = 500 mL
IV infusion: 125·12 = 1500 mL
IV antibiotic: 1·100 = 100 mL
total intake = 2100 mL
Total output
300 + 450 + 200 + 275 + 120 = 1345 mL
Balance
B = 2100 − 1345 = 755 mL
Answer
B = 755 mL
Positive: more fluid went in than came out.
4.IV fluids & fluid balance
Answer: V = 200 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.