Practice exercise (made-up values, not clinical guidance). A woman is 153 cm tall and weighs 42 kg. Find the actual weight as a percentage of the ideal body weight, %IBW, using the Devine formula (1 in = 2.54 cm). Round to the nearest whole number.
153 cm42 kgwoman
%IBW = %
2.Enteral & parenteral nutrition calculationsHard
Practice exercise (made-up values, not clinical guidance). Over 24 hours a patient receives 2400 mL of parenteral nutrition with final concentrations of 17.5% dextrose and 5% amino acids, plus 250 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.
2400 mLdextrose 17.5%amino acids 5%lipid 250 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 1000 mL bag was started at 10:15 and runs by pump at 120 mL/h. How many mL V are left in the bag at 15:45?
1000 mL120 mL/h10:15 → 15:45
V = mL
3Solutions
1.Enteral & parenteral nutrition calculations
Answer: %IBW = 91 %
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.
Ideal body weight (Devine)
153 cm/2.54 = 60.24 in
IBW = 45.5 + 2.3·(60.24 − 60) = 46.04 kg
Percentage of ideal body weight
%IBW = 42/46.04·100 = 91.22 ≈ 91%
Answer
%IBW = 91%
2.Enteral & parenteral nutrition calculations
Answer: NPC : N = 89
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: 17.5·2400/100 = 420 g
amino acids: 5·2400/100 = 120 g
Kilocalories per component
dextrose: 420·3.4 = 1428 kcal
amino acids: 120·4 = 480 kcal
lipid: 250·1.1 = 275 kcal
Non-protein kcal and nitrogen
NPC = 1428 + 275 = 1703 kcal
N = 120/6.25 = 19.2 g
Ratio
NPC : N = 1703/19.2 = 88.7 ≈ 89 : 1
Answer
NPC : N = 89
Ratios of about 150 : 1 are typical for stable patients; lower ratios give relatively more protein.
3.IV fluids & fluid balance
Answer: B = 475 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 + 240 + 350 = 740 mL
IV infusion: 80·12 = 960 mL
IV antibiotic: 1·100 = 100 mL
total intake = 1800 mL
Total output
175 + 375 + 425 + 350 = 1325 mL
Balance
B = 1800 − 1325 = 475 mL
Answer
B = 475 mL
Positive: more fluid went in than came out.
4.IV fluids & fluid balance
Answer: V = 340 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.